diff --git a/CMakeLists.txt b/CMakeLists.txt
index 04c20c51..2a2e849f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -125,9 +125,14 @@ option(ENABLE_SOUND     "Set to OFF to disable building SimGear's sound support"
 option(USE_AEONWAVE     "Set to ON to use AeonWave instead of OpenAL" ON)
 option(ENABLE_PKGUTIL   "Set to ON to build the sg_pkgutil application (default)" ON)
 option(ENABLE_DNS       "Set to ON to use udns library and DNS service resolver" ON)
-option(ENABLE_SIMD      "Enable SSE/SSE2 support for x86 compilers" ON)
+option(ENABLE_SIMD      "Enable SSE/SSE2 support for compilers" ON)
+option(ENABLE_SIMD_CODE	"Enable SSE/SSE2 support code for compilers" OFF)
 option(ENABLE_OPENMP    "Enable OpenMP compiler support" OFF)
 
+if (NOT ENABLE_SIMD AND ENABLE_SIMD_CODE)
+  set(ENABLE_SIMD_CODE OFF)
+endif()
+
 include (DetectArch)
 
 # until the fstream fix is applied and generally available in OSG,
@@ -412,8 +417,8 @@ if(CMAKE_COMPILER_IS_GNUCXX)
         "${CMAKE_CXX_FLAGS} -O0 -fno-omit-frame-pointer -fno-inline")
     elseif (ENABLE_SIMD)
       if (X86 OR X86_64)
-        set(CMAKE_C_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse")
-        set(CMAKE_CXX_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse")
+        set(CMAKE_C_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse -ftree-vectorize -ftree-slp-vectorize")
+        set(CMAKE_CXX_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse -ftree-vectorize -ftree-slp-vectorize")
       endif()
     endif()
 
@@ -440,8 +445,8 @@ if (CLANG)
         "${CMAKE_CXX_FLAGS} -O0 -fno-omit-frame-pointer -fno-inline-functions")
     elseif (ENABLE_SIMD)
       if (X86 OR X86_64)
-        set(CMAKE_C_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse")
-        set(CMAKE_CXX_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse")
+        set(CMAKE_C_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse -ftree-vectorize -ftree-slp-vectorize")
+        set(CMAKE_CXX_FLAGS_RELEASE "-O3 -msse2 -mfpmath=sse -ftree-vectorize -ftree-slp-vectorize")
       endif()
     endif()
 endif()
diff --git a/simgear/canvas/ShivaVG/src/shPath.c b/simgear/canvas/ShivaVG/src/shPath.c
index 835fcd08..9c2c1ba2 100644
--- a/simgear/canvas/ShivaVG/src/shPath.c
+++ b/simgear/canvas/ShivaVG/src/shPath.c
@@ -1193,7 +1193,7 @@ VG_API_CALL VGboolean vgInterpolatePath(VGPath dstPath, VGPath startPath,
   SHfloat *procData1, *procData2;
   SHint procSegCount1=0, procSegCount2=0;
   SHint procDataCount1=0, procDataCount2=0;
-  SHuint8 *newSegs, *newData;
+  SHuint8 *newSegs, *newData=0;
   void *userData[4];
   SHint segment1, segment2;
   SHint segindex, s,d,i;
diff --git a/simgear/canvas/elements/CanvasText.cxx b/simgear/canvas/elements/CanvasText.cxx
index ab226be3..3051045f 100644
--- a/simgear/canvas/elements/CanvasText.cxx
+++ b/simgear/canvas/elements/CanvasText.cxx
@@ -71,8 +71,12 @@ namespace canvas
 
       canvas::Text *_text_element;
 
-      void computePositions(unsigned int contextID) const override;
-  };
+#if OSG_VERSION_LESS_THAN(3,5,6)
+     void computePositions(unsigned int contextID) const override;
+#else
+     void computePositionsImplementation() override;
+#endif
+};
 
   class TextLine
   {
@@ -122,6 +126,8 @@ namespace canvas
 
     _quads = &text->_textureGlyphQuadMap.begin()->second;
 
+
+#if OSG_VERSION_LESS_THAN(3,5,6)
     GlyphQuads::LineNumbers const& line_numbers = _quads->_lineNumbers;
     GlyphQuads::LineNumbers::const_iterator begin_it =
       std::lower_bound(line_numbers.begin(), line_numbers.end(), _line);
@@ -133,6 +139,10 @@ namespace canvas
     _begin = begin_it - line_numbers.begin();
     _end = std::upper_bound(begin_it, line_numbers.end(), _line)
          - line_numbers.begin();
+#else
+//OSG:TODO: Need 3.5.6 version of this
+
+#endif
   }
 
   //----------------------------------------------------------------------------
@@ -162,33 +172,35 @@ namespace canvas
     if( empty() )
       return pos;
 #if OSG_VERSION_LESS_THAN(3,3,5)
-    GlyphQuads::Coords2 const& coords = _quads->_coords;
-#else
-    GlyphQuads::Coords2 refCoords = _quads->_coords;
-    GlyphQuads::Coords2::element_type &coords = *refCoords.get();
-#endif
-    size_t global_i = _begin + i;
+      GlyphQuads::Coords2 const& coords = _quads->_coords;
+#elif OSG_VERSION_LESS_THAN(3,5,6)
+      GlyphQuads::Coords2 refCoords = _quads->_coords;
+      GlyphQuads::Coords2::element_type &coords = *refCoords.get();
+      size_t global_i = _begin + i;
 
-    if( global_i == _begin )
-      // before first character of line
-      pos.x() = coords[_begin * 4].x();
-    else if( global_i == _end )
-      // After Last character of line
-      pos.x() = coords[(_end - 1) * 4 + 2].x();
-    else
-    {
-      float prev_l = coords[(global_i - 1) * 4].x(),
-            prev_r = coords[(global_i - 1) * 4 + 2].x(),
-            cur_l = coords[global_i * 4].x();
-
-      if( prev_l == prev_r )
-        // If previous character width is zero set to begin of next character
-        // (Happens eg. with spaces)
-        pos.x() = cur_l;
+      if (global_i == _begin)
+          // before first character of line
+          pos.x() = coords[_begin * 4].x();
+      else if (global_i == _end)
+          // After Last character of line
+          pos.x() = coords[(_end - 1) * 4 + 2].x();
       else
-        // position at center between characters
-        pos.x() = 0.5 * (prev_r + cur_l);
-    }
+      {
+          float prev_l = coords[(global_i - 1) * 4].x(),
+              prev_r = coords[(global_i - 1) * 4 + 2].x(),
+              cur_l = coords[global_i * 4].x();
+
+          if (prev_l == prev_r)
+              // If previous character width is zero set to begin of next character
+              // (Happens eg. with spaces)
+              pos.x() = cur_l;
+          else
+              // position at center between characters
+              pos.x() = 0.5 * (prev_r + cur_l);
+      }
+#else
+//OSG:TODO: need 3.5.7 version of this.
+#endif
 
     return pos;
   }
@@ -200,12 +212,12 @@ namespace canvas
       return cursorPos(0);
 
     GlyphQuads::Glyphs const& glyphs = _quads->_glyphs;
-    #if OSG_VERSION_LESS_THAN(3,3,5)
+#if OSG_VERSION_LESS_THAN(3,3,5)
     GlyphQuads::Coords2 const& coords = _quads->_coords;
-#else
+#elif OSG_VERSION_LESS_THAN(3,5,6)
+
     GlyphQuads::Coords2 refCoords = _quads->_coords;
     GlyphQuads::Coords2::element_type &coords = *refCoords.get();
-#endif
 
     float const HIT_FRACTION = 0.6;
     float const character_width = _text->getCharacterHeight()
@@ -225,6 +237,10 @@ namespace canvas
     }
 
     return cursorPos(i - _begin);
+#else
+//OSG:TODO: need 3.5.7 version of this.
+	return cursorPos(0);
+#endif
   }
 
   //----------------------------------------------------------------------------
@@ -640,7 +656,7 @@ namespace canvas
     return bb;
   }
 
-  //----------------------------------------------------------------------------
+#if OSG_VERSION_LESS_THAN(3,5,6)
   void Text::TextOSG::computePositions(unsigned int contextID) const
   {
     if( _textureGlyphQuadMap.empty() || _layout == VERTICAL )
@@ -710,6 +726,14 @@ namespace canvas
     return osgText::Text::computePositions(contextID);
   }
 
+#else
+  void Text::TextOSG::computePositionsImplementation() 
+  {
+          TextBase::computePositionsImplementation();
+  }
+#endif
+ //----------------------------------------------------------------------------
+
   //----------------------------------------------------------------------------
   const std::string Text::TYPE_NAME = "text";
 
diff --git a/simgear/debug/logstream.cxx b/simgear/debug/logstream.cxx
index eeda8901..93ba61b5 100644
--- a/simgear/debug/logstream.cxx
+++ b/simgear/debug/logstream.cxx
@@ -518,7 +518,7 @@ public:
 
         // SG_OSG (OSG notify) - will always be displayed regardless of FG log settings as OSG log level is configured 
         // separately and thus it makes more sense to allow these message through.
-        if (p == SG_OSG) return true;
+        if (static_cast<unsigned>(p) == static_cast<unsigned>(SG_OSG)) return true;
 
         p = translatePriority(p);
         if (p >= SG_INFO) return true;
diff --git a/simgear/environment/precipitation.cxx b/simgear/environment/precipitation.cxx
index 1a2b8130..97e58d3a 100644
--- a/simgear/environment/precipitation.cxx
+++ b/simgear/environment/precipitation.cxx
@@ -44,6 +44,10 @@ SGPrecipitation::SGPrecipitation() :
 void SGPrecipitation::setEnabled( bool value )
 {
     _enabled = value;
+    if (!_enabled) {
+        _precipitationEffect->snow(0);
+        _precipitationEffect->rain(0);
+    }
 }
 
 void SGPrecipitation::setDropletExternal( bool value )
@@ -64,6 +68,9 @@ bool SGPrecipitation::getEnabled() const
  */
 osg::Group* SGPrecipitation::build(void)
 {
+    if (!_enabled) 
+        return nullptr;
+
     osg::ref_ptr<osg::Group> group = new osg::Group;
 
     _precipitationEffect->snow(0);	
@@ -227,6 +234,9 @@ void SGPrecipitation::setWindProperty(double heading, double speed)
  */
 bool SGPrecipitation::update(void)
 {
+    if (!_enabled)
+        return false;
+
     if (this->_freeze) {
         if (this->_rain_intensity > 0) {
 		this->_snow_intensity = this->_rain_intensity;
diff --git a/simgear/io/HTTPClient.cxx b/simgear/io/HTTPClient.cxx
index fe6fa737..0c31354b 100644
--- a/simgear/io/HTTPClient.cxx
+++ b/simgear/io/HTTPClient.cxx
@@ -273,6 +273,10 @@ void Client::makeRequest(const Request_ptr& r)
     curl_easy_setopt(curlRequest, CURLOPT_USERAGENT, d->userAgent.c_str());
     curl_easy_setopt(curlRequest, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
 
+    if (sglog().would_log(SG_TERRASYNC, SG_DEBUG)) {
+        curl_easy_setopt(curlRequest, CURLOPT_VERBOSE, 1);
+    }
+
     curl_easy_setopt(curlRequest, CURLOPT_FOLLOWLOCATION, 1);
 
     if (!d->proxy.empty()) {
diff --git a/simgear/io/sg_file.cxx b/simgear/io/sg_file.cxx
index be629e7e..fcba988e 100644
--- a/simgear/io/sg_file.cxx
+++ b/simgear/io/sg_file.cxx
@@ -64,6 +64,31 @@ SGFile::SGFile( int existingFd ) :
 SGFile::~SGFile() {
 }
 
+#include <simgear/misc/sg_hash.hxx>
+#include <simgear/structure/exception.hxx>
+#include "simgear/misc/strutils.hxx"
+
+std::string SGFile::computeHash()
+{
+    if (!file_name.exists())
+        return std::string();
+    simgear::sha1nfo info;
+    sha1_init(&info);
+    char* buf = static_cast<char*>(malloc(1024 * 1024));
+    size_t readLen;
+    SGBinaryFile f(file_name);
+    if (!f.open(SG_IO_IN)) {
+        throw sg_io_exception("Couldn't open file for compute hash", file_name);
+    }
+    while ((readLen = f.read(buf, 1024 * 1024)) > 0) {
+        sha1_write(&info, buf, readLen);
+    }
+
+    f.close();
+    free(buf);
+    std::string hashBytes((char*)sha1_result(&info), HASH_LENGTH);
+    return simgear::strutils::encodeHex(hashBytes);
+}
 
 // open the file based on specified direction
 bool SGFile::open( const SGProtocolDir d ) {
diff --git a/simgear/io/sg_file.hxx b/simgear/io/sg_file.hxx
index 613f097c..59de6ba7 100644
--- a/simgear/io/sg_file.hxx
+++ b/simgear/io/sg_file.hxx
@@ -87,6 +87,9 @@ public:
 
     /** @return true of eof conditions exists */
     virtual bool eof() const { return eof_flag; };
+
+    std::string computeHash();
+
 };
 
 class SGBinaryFile : public SGFile {
diff --git a/simgear/math/simd.hxx b/simgear/math/simd.hxx
index a2847775..162820ac 100644
--- a/simgear/math/simd.hxx
+++ b/simgear/math/simd.hxx
@@ -309,7 +309,7 @@ inline simd4_t<T,N> operator*(simd4_t<T,N> v, T f) {
     return v;
 }
 
-#ifdef ENABLE_SIMD
+#ifdef ENABLE_SIMD_CODE
 
 # ifdef __SSE__
 namespace simd4
@@ -1305,7 +1305,7 @@ inline simd4_t<int,N> max(simd4_t<int,N> v1, const simd4_t<int,N>& v2) {
 
 # endif
 
-#endif /* ENABLE_SIMD */
+#endif /* ENABLE_SIMD_CODE */
 
 #endif /* __SIMD_H__ */
 
diff --git a/simgear/math/simd4x4.hxx b/simgear/math/simd4x4.hxx
index 69203511..26db560f 100644
--- a/simgear/math/simd4x4.hxx
+++ b/simgear/math/simd4x4.hxx
@@ -289,7 +289,7 @@ inline simd4x4_t<T,N> operator*(const simd4x4_t<T,N>& m1, const simd4x4_t<T,N>&
 }
 
 
-#ifdef ENABLE_SIMD
+#ifdef ENABLE_SIMD_CODE
 
 # ifdef __SSE__
 template<>
@@ -1191,7 +1191,7 @@ inline simd4_t<int,3> transform<int>(const simd4x4_t<int,4>& m, const simd4_t<in
 } /* namespace simd4x */
 # endif
 
-#endif /* ENABLE_SIMD */
+#endif /* ENABLE_SIMD_CODE */
 
 #endif /* __SIMD4X4_H__ */
 
diff --git a/simgear/props/props.cxx b/simgear/props/props.cxx
index 1c21ecee..8b599632 100644
--- a/simgear/props/props.cxx
+++ b/simgear/props/props.cxx
@@ -963,6 +963,11 @@ SGPropertyNode::alias (SGPropertyNode * target)
 {
   if (target && (_type != props::ALIAS) && (!_tied))
   {
+   /* loop protection: check alias chain; must not contain self */
+    for (auto p = target; p; p = ((p->_type == props::ALIAS) ? p->_value.alias : nullptr)) {
+      if (p == this) return false;
+    }
+      
     clearValue();
     get(target);
     _value.alias = target;
@@ -973,7 +978,7 @@ SGPropertyNode::alias (SGPropertyNode * target)
   if (!target)
   {
     SG_LOG(SG_GENERAL, SG_ALERT,
-           "Failed to create alias for " << getPath() << ". "
+           "Failed to set alias " << getPath() << ". "
            "The target property does not exist.");
   }
   else
@@ -981,15 +986,15 @@ SGPropertyNode::alias (SGPropertyNode * target)
   {
     if (_value.alias == target)
         return true; // ok, identical alias requested
-    SG_LOG(SG_GENERAL, SG_ALERT,
-           "Failed to create alias at " << target->getPath() << ". "
-           "Source "<< getPath() << " is already aliasing another property.");
+    SG_LOG(SG_GENERAL, SG_ALERT, "alias(): "<< getPath() <<
+        " is already pointing to " << _value.alias->getPath() <<
+        " so it cannot alias '" << target->getPath() << ". Use unalias() first.");
   }
   else
   if (_tied)
   {
-    SG_LOG(SG_GENERAL, SG_ALERT, "Failed to create alias at " << target->getPath() << ". "
-           "Source " << getPath() << " is a tied property.");
+    SG_LOG(SG_GENERAL, SG_ALERT, "alias(): " << getPath() << 
+        " is a tied property. It cannot alias " << target->getPath() << ".");
   }
 
   return false;
diff --git a/simgear/scene/material/Effect.cxx b/simgear/scene/material/Effect.cxx
index 70792a7a..72f5fba1 100644
--- a/simgear/scene/material/Effect.cxx
+++ b/simgear/scene/material/Effect.cxx
@@ -830,6 +830,9 @@ void reload_shaders()
         if (!fileName.empty()) {
             shader->loadShaderSourceFromFile(fileName);
         }
+        else
+            SG_LOG(SG_INPUT, SG_ALERT, "Could not locate shader: " << fileName);
+
     }
 }
 
@@ -917,8 +920,13 @@ void ShaderProgramBuilder::buildAttribute(Effect* effect, Pass* pass,
         Shader::Type stype = (Shader::Type)shaderKey.second;
         string fileName = SGModelLib::findDataFile(shaderName, options);
         if (fileName.empty())
+        {
+            SG_LOG(SG_INPUT, SG_ALERT, "Could not locate shader" << shaderName);
+
+
             throw BuilderException(string("couldn't find shader ") +
-                                   shaderName);
+                shaderName);
+        }
         resolvedKey.shaders.push_back(ShaderKey(fileName, stype));
     }
     ProgramMap::iterator resitr = resolvedProgramMap.find(resolvedKey);
@@ -1405,8 +1413,11 @@ bool makeParametersFromStateSet(SGPropertyNode* effectRoot, const StateSet* ss)
 
 // Walk the techniques property tree, building techniques and
 // passes.
+static SGMutex  realizeTechniques_lock;
 bool Effect::realizeTechniques(const SGReaderWriterOptions* options)
 {
+    SGGuard<SGMutex> g(realizeTechniques_lock);
+
     if (_isRealized)
         return true;
     PropertyList tniqList = root->getChildren("technique");
diff --git a/simgear/scene/material/TextureBuilder.cxx b/simgear/scene/material/TextureBuilder.cxx
index fa571912..43343169 100644
--- a/simgear/scene/material/TextureBuilder.cxx
+++ b/simgear/scene/material/TextureBuilder.cxx
@@ -76,7 +76,7 @@ osg::Texture* TextureBuilder::buildFromType(Effect* effect, Pass* pass, const st
 
 typedef boost::tuple<string, Texture::FilterMode, Texture::FilterMode,
                      Texture::WrapMode, Texture::WrapMode, Texture::WrapMode,
-                     string, MipMapTuple> TexTuple;
+                     string, MipMapTuple, ImageInternalFormat> TexTuple;
 
 EffectNameValue<TexEnv::Mode> texEnvModesInit[] =
 {
@@ -239,6 +239,17 @@ TexTuple makeTexTuple(Effect* effect, const SGPropertyNode* props,
         }
     }
 
+    const SGPropertyNode* pInternalFormat = getEffectPropertyChild(effect, props, "internal-format");
+    pInternalFormat = props->getChild("internal-format");
+    ImageInternalFormat iformat = ImageInternalFormat::Unspecified;
+    if (pInternalFormat) {
+        std::string internalFormat = pInternalFormat->getStringValue();
+        if (internalFormat == "normalized") {
+            iformat = ImageInternalFormat::Normalized;
+            SG_LOG(SG_INPUT, SG_ALERT, "internal-format normalized '" << imageName << "'");
+        }
+    }
+
     const SGPropertyNode* pMipmapControl
         = getEffectPropertyChild(effect, props, "mipmap-control");
     MipMapTuple mipmapFunctions( AUTOMATIC, AUTOMATIC, AUTOMATIC, AUTOMATIC );
@@ -246,7 +257,7 @@ TexTuple makeTexTuple(Effect* effect, const SGPropertyNode* props,
         mipmapFunctions = makeMipMapTuple(effect, pMipmapControl, options);
 
     return TexTuple(absFileName, minFilter, magFilter, sWrap, tWrap, rWrap,
-                    texType, mipmapFunctions);
+                    texType, mipmapFunctions, iformat);
 }
 
 bool setAttrs(const TexTuple& attrs, Texture* tex,
@@ -257,7 +268,19 @@ bool setAttrs(const TexTuple& attrs, Texture* tex,
         return false;
 
     osgDB::ReaderWriter::ReadResult result;
+
+    // load texture for effect
+    SGReaderWriterOptions::LoadOriginHint origLOH = options->getLoadOriginHint();
+    if(attrs.get<8>() == ImageInternalFormat::Normalized)
+        options->setLoadOriginHint(SGReaderWriterOptions::LoadOriginHint::ORIGIN_EFFECTS_NORMALIZED);
+    else
+        options->setLoadOriginHint(SGReaderWriterOptions::LoadOriginHint::ORIGIN_EFFECTS);
+#if OSG_VERSION_LESS_THAN(3,4,2)
     result = osgDB::readImageFile(imageName, options);
+#else
+    result = osgDB::readRefImageFile(imageName, options);
+#endif
+    options->setLoadOriginHint(origLOH);
     osg::ref_ptr<osg::Image> image;
     if (result.success())
         image = result.getImage();
@@ -585,36 +608,64 @@ Texture* CubeMapBuilder::build(Effect* effect, Pass* pass, const SGPropertyNode*
         cubeTexture->setWrap(osg::Texture3D::WRAP_R, osg::Texture::CLAMP_TO_EDGE);
 
         osgDB::ReaderWriter::ReadResult result;
+        SGReaderWriterOptions* wOpts = (SGReaderWriterOptions*)options;
+        SGReaderWriterOptions::LoadOriginHint origLOH = wOpts->getLoadOriginHint();
+        wOpts->setLoadOriginHint(SGReaderWriterOptions::LoadOriginHint::ORIGIN_EFFECTS);
+#if OSG_VERSION_LESS_THAN(3,4,0)
         result = osgDB::readImageFile(_tuple.get<0>(), options);
+#else
+        result = osgDB::readRefImageFile(_tuple.get<0>(), options);
+#endif
         if(result.success()) {
             osg::Image* image = result.getImage();
             cubeTexture->setImage(TextureCubeMap::POSITIVE_X, image);
         }
+#if OSG_VERSION_LESS_THAN(3,4,0)
         result = osgDB::readImageFile(_tuple.get<1>(), options);
+#else
+        result = osgDB::readRefImageFile(_tuple.get<1>(), options);
+#endif
         if(result.success()) {
             osg::Image* image = result.getImage();
             cubeTexture->setImage(TextureCubeMap::NEGATIVE_X, image);
         }
+#if OSG_VERSION_LESS_THAN(3,4,0)
         result = osgDB::readImageFile(_tuple.get<2>(), options);
+#else
+        result = osgDB::readRefImageFile(_tuple.get<2>(), options);
+#endif
         if(result.success()) {
             osg::Image* image = result.getImage();
             cubeTexture->setImage(TextureCubeMap::POSITIVE_Y, image);
         }
+#if OSG_VERSION_LESS_THAN(3,4,0)
         result = osgDB::readImageFile(_tuple.get<3>(), options);
+#else
+        result = osgDB::readRefImageFile(_tuple.get<3>(), options);
+#endif
         if(result.success()) {
             osg::Image* image = result.getImage();
             cubeTexture->setImage(TextureCubeMap::NEGATIVE_Y, image);
         }
+#if OSG_VERSION_LESS_THAN(3,4,0)
         result = osgDB::readImageFile(_tuple.get<4>(), options);
+#else
+        result = osgDB::readRefImageFile(_tuple.get<4>(), options);
+#endif
         if(result.success()) {
             osg::Image* image = result.getImage();
             cubeTexture->setImage(TextureCubeMap::POSITIVE_Z, image);
         }
+#if OSG_VERSION_LESS_THAN(3,4,0)
         result = osgDB::readImageFile(_tuple.get<5>(), options);
+#else
+        result = osgDB::readRefImageFile(_tuple.get<5>(), options);
+#endif
         if(result.success()) {
             osg::Image* image = result.getImage();
             cubeTexture->setImage(TextureCubeMap::NEGATIVE_Z, image);
         }
+        wOpts->setLoadOriginHint(origLOH);
 
         if (itr == _cubemaps.end())
             _cubemaps[_tuple] = cubeTexture;
@@ -634,7 +685,11 @@ Texture* CubeMapBuilder::build(Effect* effect, Pass* pass, const SGPropertyNode*
             return cubeTexture.release();
 
         osgDB::ReaderWriter::ReadResult result;
+#if OSG_VERSION_LESS_THAN(3,4,0)
         result = osgDB::readImageFile(texname, options);
+#else
+        result = osgDB::readRefImageFile(texname, options);
+#endif
         if(result.success()) {
             osg::Image* image = result.getImage();
             image->flipVertical();   // Seems like the image coordinates are somewhat funny, flip to get better ones
diff --git a/simgear/scene/material/mat.cxx b/simgear/scene/material/mat.cxx
index 916d4cbd..0eaa37a6 100644
--- a/simgear/scene/material/mat.cxx
+++ b/simgear/scene/material/mat.cxx
@@ -227,7 +227,11 @@ SGMaterial::read_properties(const SGReaderWriterOptions* options,
             }
             else
             {
+#if OSG_VERSION_LESS_THAN(3,4,0)
                 osg::Image* image = osgDB::readImageFile(fullMaskPath, options);
+#else
+                osg::Image* image = osgDB::readRefImageFile(fullMaskPath, options);
+#endif
                 if (image && image->valid())
                 {
                     Texture2DRef object_mask = new osg::Texture2D;
diff --git a/simgear/scene/material/mipmap.hxx b/simgear/scene/material/mipmap.hxx
index 0a908c59..75b29231 100644
--- a/simgear/scene/material/mipmap.hxx
+++ b/simgear/scene/material/mipmap.hxx
@@ -31,14 +31,18 @@ class Effect;
 class SGReaderWriterOptions;
 
 namespace effect {
-enum MipMapFunction {
-    AUTOMATIC,
-    AVERAGE,
-    SUM,
-    PRODUCT,
-    MIN,
-    MAX
-};
+    enum MipMapFunction {
+        AUTOMATIC,
+        AVERAGE,
+        SUM,
+        PRODUCT,
+        MIN,
+        MAX
+    };
+    enum ImageInternalFormat {
+        Unspecified,
+        Normalized,
+    };
 
 typedef boost::tuple<MipMapFunction, MipMapFunction, MipMapFunction, MipMapFunction> MipMapTuple;
 
diff --git a/simgear/scene/model/BVHDebugCollectVisitor.hxx b/simgear/scene/model/BVHDebugCollectVisitor.hxx
index e99779ff..8e7be665 100644
--- a/simgear/scene/model/BVHDebugCollectVisitor.hxx
+++ b/simgear/scene/model/BVHDebugCollectVisitor.hxx
@@ -111,6 +111,11 @@ public:
         if (transform->getNumChildren())
             _group->addChild(transform.get());
     }
+    virtual void apply(BVHPageNode& leaf)
+    {
+        leaf.traverse(*this);
+    }
+
     virtual void apply(BVHLineGeometry&)
     {
     }
diff --git a/simgear/scene/model/BVHPageNodeOSG.cxx b/simgear/scene/model/BVHPageNodeOSG.cxx
index e8051847..a2f15bcb 100644
--- a/simgear/scene/model/BVHPageNodeOSG.cxx
+++ b/simgear/scene/model/BVHPageNodeOSG.cxx
@@ -215,7 +215,11 @@ public:
                 if (pagedLOD.getMinRange(i) <= 0) {
                     osg::ref_ptr<const osgDB::Options> options;
                     options = getOptions(pagedLOD.getDatabaseOptions(), pagedLOD.getDatabasePath());
+#if OSG_VERSION_LESS_THAN(3,4,0)
+                    node = osgDB::readNodeFile(pagedLOD.getFileName(i), options.get());
+#else
                     node = osgDB::readRefNodeFile(pagedLOD.getFileName(i), options.get());
+#endif
                 }
                 if (!node.valid())
                     node = new osg::Group;
@@ -256,7 +260,11 @@ public:
             osg::ref_ptr<const osgDB::Options> options;
             options = getOptions(proxyNode.getDatabaseOptions(), proxyNode.getDatabasePath());
             osg::ref_ptr<osg::Node> node;
+#if OSG_VERSION_LESS_THAN(3,4,0)
+            node = osgDB::readNodeFile(proxyNode.getFileName(i), options.get());
+#else
             node = osgDB::readRefNodeFile(proxyNode.getFileName(i), options.get());
+#endif
             if (!node.valid())
                 node = new osg::Group;
             if (i < proxyNode.getNumChildren())
@@ -353,7 +361,11 @@ SGSharedPtr<BVHNode>
 BVHPageNodeOSG::load(const std::string& name, const osg::ref_ptr<const osg::Referenced>& options)
 {
     osg::ref_ptr<osg::Node> node;
+#if OSG_VERSION_LESS_THAN(3,4,0)
+    node = osgDB::readNodeFile(name, dynamic_cast<const osgDB::Options*>(options.get()));
+#else
     node = osgDB::readRefNodeFile(name, dynamic_cast<const osgDB::Options*>(options.get()));
+#endif
     if (!node.valid())
         return SGSharedPtr<BVHNode>();
 
diff --git a/simgear/scene/model/ModelRegistry.cxx b/simgear/scene/model/ModelRegistry.cxx
index 4451fd79..ca2beb1f 100644
--- a/simgear/scene/model/ModelRegistry.cxx
+++ b/simgear/scene/model/ModelRegistry.cxx
@@ -60,6 +60,8 @@
 #include <simgear/props/props.hxx>
 #include <simgear/props/props_io.hxx>
 #include <simgear/props/condition.hxx>
+#include <simgear/io/sg_file.hxx>
+#include <simgear/threads/SGGuard.hxx>
 
 #include "BoundingVolumeBuildVisitor.hxx"
 #include "model.hxx"
@@ -180,9 +182,34 @@ public:
 
 } // namespace
 
-static bool isPowerOfTwo(int width, int height)
+static int nearestPowerOfTwo(unsigned int _v)
 {
-    return (((width & (width - 1)) == 0) && ((height & (height - 1))) == 0);
+    //    uint v; // compute the next highest power of 2 of 32-bit v
+    unsigned int v = (unsigned int)_v;
+    bool neg = _v < 0;
+    if (neg)
+        v = (unsigned int)(-_v);
+
+    v &= (2 << 16) - 1; // make +ve
+
+    // bit twiddle to round up to nearest pot.
+    v--;
+    v |= v >> 1;
+    v |= v >> 2;
+    v |= v >> 4;
+    v |= v >> 8;
+    v |= v >> 16;
+    v++;
+
+    if (neg)
+        _v = -(int)v;
+    else
+        _v = (int)v;
+    return v;
+}
+    static bool isPowerOfTwo(int v)
+{
+    return ((v & (v - 1)) == 0);
 }
 osg::Node* DefaultProcessPolicy::process(osg::Node* node, const std::string& filename,
     const Options* opt)
@@ -205,6 +232,139 @@ osg::Image* getImageByName(const std::string& filename)
     return nullptr;
 }
 #endif
+// a cache which evicts the least recently used item when it is full
+#include <map>
+#include <list>
+#include <utility>
+
+#include <boost/optional.hpp>
+template<class Key, class Value>
+class lru_cache
+{
+public:
+    SGMutex _mutex;
+
+    typedef Key key_type;
+    typedef Value value_type;
+    typedef std::list<key_type> list_type;
+    typedef std::map<
+        key_type,
+        std::pair<value_type, typename list_type::iterator>
+    > map_type;
+
+    lru_cache(size_t capacity)
+        : m_capacity(capacity)
+    {
+    }
+
+    ~lru_cache()
+    {
+    }
+
+
+    size_t size() const
+    {
+        return m_map.size();
+    }
+
+    size_t capacity() const
+    {
+        return m_capacity;
+    }
+
+    bool empty() const
+    {
+        return m_map.empty();
+    }
+
+    bool contains(const key_type &key)
+    {
+        SGGuard<SGMutex> scopeLock(_mutex);
+        return m_map.find(key) != m_map.end();
+    }
+
+    void insert(const key_type &key, const value_type &value)
+    {
+        SGGuard<SGMutex> scopeLock(_mutex);
+        typename map_type::iterator i = m_map.find(key);
+        if (i == m_map.end()) {
+            // insert item into the cache, but first check if it is full
+            if (size() >= m_capacity) {
+                // cache is full, evict the least recently used item
+                evict();
+            }
+
+            // insert the new item
+            m_list.push_front(key);
+            m_map[key] = std::make_pair(value, m_list.begin());
+        }
+    }
+    boost::optional<key_type> findValue(const std::string &requiredValue)
+    {
+        SGGuard<SGMutex> scopeLock(_mutex);
+        for (typename map_type::iterator it = m_map.begin(); it != m_map.end(); ++it)
+            if (it->second.first == requiredValue)
+                return it->first;
+        return boost::none;
+    }
+    boost::optional<value_type> get(const key_type &key)
+    {
+        SGGuard<SGMutex> scopeLock(_mutex);
+        // lookup value in the cache
+        typename map_type::iterator i = m_map.find(key);
+        if (i == m_map.end()) {
+            // value not in cache
+            return boost::none;
+        }
+
+        // return the value, but first update its place in the most
+        // recently used list
+        typename list_type::iterator j = i->second.second;
+        if (j != m_list.begin()) {
+            // move item to the front of the most recently used list
+            m_list.erase(j);
+            m_list.push_front(key);
+
+            // update iterator in map
+            j = m_list.begin();
+            const value_type &value = i->second.first;
+            m_map[key] = std::make_pair(value, j);
+
+            // return the value
+            return value;
+        }
+        else {
+            // the item is already at the front of the most recently
+            // used list so just return it
+            return i->second.first;
+        }
+    }
+
+    void clear()
+    {
+        SGGuard<SGMutex> scopeLock(_mutex);
+        m_map.clear();
+        m_list.clear();
+    }
+
+private:
+    void evict()
+    {
+        SGGuard<SGMutex> scopeLock(_mutex);
+        // evict item from the end of most recently used list
+        typename list_type::iterator i = --m_list.end();
+        m_map.erase(*i);
+        m_list.erase(i);
+    }
+
+private:
+    map_type m_map;
+    list_type m_list;
+    size_t m_capacity;
+};
+lru_cache < std::string, std::string> filename_hash_cache(100000);
+lru_cache < std::string, bool> filesCleaned(100000);
+static bool refreshCache = false;
 
 ReaderWriter::ReadResult
 ModelRegistry::readImage(const string& fileName,
@@ -248,6 +408,8 @@ ModelRegistry::readImage(const string& fileName,
 
     if (cache_active) {
         if (fileExtension != "dds" && fileExtension != "gz") {
+            const SGReaderWriterOptions* sgoptC = dynamic_cast<const SGReaderWriterOptions*>(opt);
+
             std::string root = getPathRoot(absFileName);
             std::string prr = getPathRelative(root, absFileName);
             std::string cache_root = SGSceneFeatures::instance()->getTextureCompressionPath().c_str();
@@ -255,99 +417,231 @@ ModelRegistry::readImage(const string& fileName,
 
             SGPath file(absFileName);
             std::stringstream tstream;
-            tstream << std::hex << file.modTime();
-            newName += "." + tstream.str();
 
-            newName += ".cache.dds";
-            if (!fileExists(newName)) {
-                res = registry->readImageImplementation(absFileName, opt);
+            // calucate and use hash for storing cached image. This also
+            // helps with sharing of identical images between models.
+            if (fileExists(absFileName)) {
+                SGFile f(absFileName);
+                std::string hash;
+                boost::optional<std::string> cachehash = filename_hash_cache.get(absFileName);
+                if (cachehash) {
+                    hash = *cachehash;
+//                    SG_LOG(SG_IO, SG_ALERT, "Hash for " + absFileName + " in cache " + hash);
+                }
+                else {
+//                  SG_LOG(SG_IO, SG_ALERT, "Creating hash for " + absFileName);
+                    hash = f.computeHash();
+                    filename_hash_cache.insert(absFileName, hash);
+                    boost::optional<std::string> cacheFilename = filename_hash_cache.findValue(hash);
 
-                if (res.validImage()) {
-                  osg::ref_ptr<osg::Image> srcImage = res.getImage();
-                  int width = srcImage->s();
-                  bool transparent = srcImage->isImageTranslucent();
-                  int height = srcImage->t();
-
-                  if (height >= max_texture_size)
-                  {
-                      SG_LOG(SG_IO, SG_WARN, "Image texture too high " << width << "," << height << absFileName);
-                      osg::ref_ptr<osg::Image> resizedImage;
-                      int factor = height / max_texture_size;
-                      if (ImageUtils::resizeImage(srcImage, width / factor, height / factor, resizedImage))
-                          srcImage = resizedImage;
-                      width = srcImage->s();
-                      height = srcImage->t();
-                  }
-                  if (width >= max_texture_size)
-                  {
-                      SG_LOG(SG_IO, SG_WARN, "Image texture too wide " << width << "," << height << absFileName);
-                      osg::ref_ptr<osg::Image> resizedImage;
-                      int factor = width / max_texture_size;
-                      if (ImageUtils::resizeImage(srcImage, width / factor, height / factor, resizedImage))
-                          srcImage = resizedImage;
-                      width = srcImage->s();
-                      height = srcImage->t();
-                  }
-
-                  //
-                  // only cache power of two textures that are of a reasonable size
-                  if (width >= 64 && height >= 64 && isPowerOfTwo(width, height)) {
-                      simgear::effect::MipMapTuple mipmapFunctions(simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE);
-
-                      SGPath filePath(newName);
-                      filePath.create_dir();
-
-                      // setup the options string for saving the texture as we don't want OSG to auto flip the texture
-                      // as this complicates loading as it requires a flag to flip it back which will preclude the
-                      // image from being cached because we will have to clone the options to set the flag and thus lose
-                      // the link to the cache in the options from the caller.
-                      osg::ref_ptr<Options> nopt;
-                      nopt = opt->cloneOptions();
-                      std::string optionstring = nopt->getOptionString();
-
-                      if (!optionstring.empty())
-                          optionstring += " ";
-
-                      nopt->setOptionString(optionstring + "ddsNoAutoFlipWrite");
-
-                      /*
-                       * decide if we need to compress this.
-                       */
-                      bool compress = (transparent && compress_transparent) || (!transparent && compress_solid);
-
-                      if (compress) {
-                          if (processor)
-                          {
-                              if (transparent)
-                                  processor->compress(*srcImage, osg::Texture::USE_S3TC_DXT5_COMPRESSION, true, true, osgDB::ImageProcessor::USE_CPU, osgDB::ImageProcessor::PRODUCTION);
-                              else
-                                  processor->compress(*srcImage, osg::Texture::USE_S3TC_DXT1_COMPRESSION, true, true, osgDB::ImageProcessor::USE_CPU, osgDB::ImageProcessor::PRODUCTION);
-                              //processor->generateMipMap(*srcImage, true, osgDB::ImageProcessor::USE_CPU);
-                          }
-                          else {
-                              simgear::effect::MipMapTuple mipmapFunctions(simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE);
-                              SG_LOG(SG_IO, SG_WARN, "Texture compression plugin (osg_nvtt) not available; storing uncompressed image: " << newName);
-                              srcImage = simgear::effect::computeMipmap(srcImage, mipmapFunctions);
-                          }
-                      }
-                      else {
-                          if (processor) {
-                              processor->generateMipMap(*srcImage, true, osgDB::ImageProcessor::USE_CPU);
-                          }
-                          else {
-                              simgear::effect::MipMapTuple mipmapFunctions(simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE);
-                              srcImage = simgear::effect::computeMipmap(srcImage, mipmapFunctions);
-                          }
-                      }
-                      registry->writeImage(*srcImage, newName, nopt);
-                      absFileName = newName;
-                  }
-              }
+                    // possibly a shared texture - but warn the user to allow investigation.
+                    if (cacheFilename && *cacheFilename != absFileName) {
+                        SG_LOG(SG_IO, SG_ALERT, " Already have " + hash + " : " + *cacheFilename + " not "+absFileName);
+                    }
+//                    SG_LOG(SG_IO, SG_ALERT, " >>>> " + hash + " :: " + newName);
+                }
+                newName = cache_root + "/" + hash.substr(0,2) + "/" + hash + ".cache.dds";
             }
             else
+            {
+                tstream << std::hex << file.modTime();
+                newName += "." + tstream.str();
+                newName += ".cache.dds";
+            }
+            bool doRefresh = refreshCache;
+            //if (fileExists(newName) && sgoptC && sgoptC->getLoadOriginHint() == SGReaderWriterOptions::LoadOriginHint::ORIGIN_EFFECTS) {
+            //    doRefresh = true;
+            //    
+            //}
+
+            if (fileExists(newName) && doRefresh) {
+                if (!filesCleaned.contains(newName)) {
+                    SG_LOG(SG_IO, SG_ALERT, "Removing previously cached effects image " + newName);
+                    SGPath(newName).remove();
+                    filesCleaned.insert(newName, true);
+                }
+
+            }
+
+            if (!fileExists(newName)) {
+                res = registry->readImageImplementation(absFileName, opt);
+                if (res.validImage()) {
+                    osg::ref_ptr<osg::Image> srcImage = res.getImage();
+                    int width = srcImage->s();
+                    bool transparent = srcImage->isImageTranslucent();
+                    bool isNormalMap = false;
+                    bool isEffect = false;
+                    /*
+                    * decide if we need to compress this.
+                    */
+                    bool can_compress = (transparent && compress_transparent) || (!transparent && compress_solid);
+
+                    int height = srcImage->t();
+
+                    // use the new file origin to determine any special processing
+                    // we handle the following
+                    // - normal maps
+                    // - images loaded from effects
+                    if (sgoptC && transparent && sgoptC->getLoadOriginHint() == SGReaderWriterOptions::LoadOriginHint::ORIGIN_EFFECTS_NORMALIZED) {
+                        isNormalMap = true;
+                    }
+                    else if (sgoptC && transparent && sgoptC->getLoadOriginHint() == SGReaderWriterOptions::LoadOriginHint::ORIGIN_EFFECTS) {
+                        SG_LOG(SG_IO, SG_ALERT, "From effects transparent " + absFileName);
+                        isEffect = true;
+//                        can_compress = false;
+                    }
+                    else if (sgoptC && transparent && sgoptC->getLoadOriginHint() == SGReaderWriterOptions::LoadOriginHint::ORIGIN_EFFECTS) {
+                        SG_LOG(SG_IO, SG_ALERT, "From effects " + absFileName);
+                        isEffect = true;
+                    }
+                    if (can_compress)
+                    {
+                        std::string pot_message;
+                        bool resize = false;
+                        if (!isPowerOfTwo(width)) {
+                            width = nearestPowerOfTwo(width);
+                            resize = true;
+                            pot_message += std::string(" not POT: resized width to ") + std::to_string(width);
+                        }
+                        if (!isPowerOfTwo(height)) {
+                            height = nearestPowerOfTwo(height);
+                            resize = true;
+                            pot_message += std::string(" not POT: resized height to ") + std::to_string(height);
+                        }
+if (pot_message.size())
+SG_LOG(SG_IO, SG_WARN, pot_message << " " << absFileName);
+
+                        // unlikely that after resizing in height the width will still be outside of the max texture size.
+                        if (height > max_texture_size)
+                        {
+                            SG_LOG(SG_IO, SG_WARN, "Image texture too high (max " << max_texture_size << ") " << width << "," << height << " " << absFileName);
+                            int factor = height / max_texture_size;
+                            height /= factor;
+                            width /= factor;
+                            resize = true;
+                        }
+                        if (width > max_texture_size)
+                        {
+                            SG_LOG(SG_IO, SG_WARN, "Image texture too wide (max " << max_texture_size << ") " << width << "," << height << " " << absFileName);
+                            int factor = width / max_texture_size;
+                            height /= factor;
+                            width /= factor;
+                            resize = true;
+                        }
+                        if (resize) {
+                            osg::ref_ptr<osg::Image> resizedImage;
+
+                            if (ImageUtils::resizeImage(srcImage, width, height, resizedImage))
+                                srcImage = resizedImage;
+                        }
+
+                        //
+                        // only cache power of two textures that are of a reasonable size
+                        if (width >= 4 && height >= 4) {
+
+                            simgear::effect::MipMapTuple mipmapFunctions(simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE);
+
+                            SGPath filePath(newName);
+                            filePath.create_dir();
+
+                            // setup the options string for saving the texture as we don't want OSG to auto flip the texture
+                            // as this complicates loading as it requires a flag to flip it back which will preclude the
+                            // image from being cached because we will have to clone the options to set the flag and thus lose
+                            // the link to the cache in the options from the caller.
+                            osg::ref_ptr<Options> nopt;
+                            nopt = opt->cloneOptions();
+                            std::string optionstring = nopt->getOptionString();
+
+                            if (!optionstring.empty())
+                                optionstring += " ";
+
+                            nopt->setOptionString(optionstring + "ddsNoAutoFlipWrite");
+
+                            //GLenum srcImageType = srcImage->getDataType();
+                            //                            printf("--- %-80s --> f=%8x t=%8x\n", newName.c_str(), srcImage->getPixelFormat(), srcImageType);
+
+                            try
+                            {
+                                if (can_compress) {
+                                    osg::Texture::InternalFormatMode targetFormat = osg::Texture::USE_S3TC_DXT1_COMPRESSION;
+                                    if (isNormalMap) {
+                                        if (transparent) {
+                                            targetFormat = osg::Texture::USE_S3TC_DXT5_COMPRESSION;
+                                        }
+                                        else
+                                            targetFormat = osg::Texture::USE_S3TC_DXT5_COMPRESSION;
+                                    }
+                                    else if (isEffect)
+                                    {
+                                        if (transparent) {
+                                            targetFormat = osg::Texture::USE_S3TC_DXT5_COMPRESSION;
+                                        }
+                                        else
+                                            targetFormat = osg::Texture::USE_S3TC_DXT1_COMPRESSION;
+                                    }
+                                    else{
+                                        if (transparent) {
+                                            targetFormat = osg::Texture::USE_S3TC_DXT3_COMPRESSION;
+                                        }
+                                        else
+                                            targetFormat = osg::Texture::USE_S3TC_DXT1_COMPRESSION;
+                                    }
+
+                                    if (processor)
+                                    {
+                                        SG_LOG(SG_IO, SG_ALERT, "Creating " << targetFormat << " for " + absFileName);
+                                        // normal maps:
+                                        // nvdxt.exe - quality_highest - rescaleKaiser - Kaiser - dxt5nm - norm
+                                        processor->compress(*srcImage, targetFormat, true, true, osgDB::ImageProcessor::USE_CPU, osgDB::ImageProcessor::PRODUCTION);
+                                        SG_LOG(SG_IO, SG_ALERT, "-- finished creating DDS: " + newName);
+                                        //processor->generateMipMap(*srcImage, true, osgDB::ImageProcessor::USE_CPU);
+                                    }
+                                    else {
+                                        simgear::effect::MipMapTuple mipmapFunctions(simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE);
+                                        SG_LOG(SG_IO, SG_WARN, "Texture compression plugin (osg_nvtt) not available; storing uncompressed image: " << absFileName);
+                                        srcImage = simgear::effect::computeMipmap(srcImage, mipmapFunctions);
+                                    }
+                                }
+                                else {
+                                    SG_LOG(SG_IO, SG_ALERT, "Creating uncompressed DDS for " + absFileName);
+                                    if (processor) {
+                                        processor->generateMipMap(*srcImage, true, osgDB::ImageProcessor::USE_CPU);
+                                    }
+                                    else {
+                                        simgear::effect::MipMapTuple mipmapFunctions(simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE);
+                                        srcImage = simgear::effect::computeMipmap(srcImage, mipmapFunctions);
+                                    }
+                                }
+                                //}
+                                //else
+                                //    printf("--- no compress or mipmap of format %s\n", newName.c_str());
+                                registry->writeImage(*srcImage, newName, nopt);
+                                {
+                                    std::string mdlDirectory = cache_root + "/cache-index.txt";
+                                    FILE *f = ::fopen(mdlDirectory.c_str(), "a");
+                                    if (f)
+                                    {
+                                        ::fprintf(f, "%s, %s\n", absFileName.c_str(), newName.c_str());
+                                        ::fclose(f);
+                                    }
+                                }
+                                absFileName = newName;
+                            }
+                            catch (...) {
+                                SG_LOG(SG_IO, SG_ALERT, "Exception processing " << absFileName << " may be corrupted");
+                            }
+                        }
+                        else
+                            SG_LOG(SG_IO, SG_WARN, absFileName + " too small " << width << "," << height);
+                    }
+                }
+            }
+            else {
                 absFileName = newName;
+            }
         }
     }
+
     res = registry->readImageImplementation(absFileName, opt);
 
     if (!res.success()) {
@@ -368,6 +662,18 @@ ModelRegistry::readImage(const string& fileName,
     if (srcImage1->getName().empty()) {
         srcImage1->setName(absFileName);
     }
+    if(cache_active && getFileExtension(absFileName) != "dds")
+    {
+        if (processor) {
+            processor->generateMipMap(*srcImage1, true, osgDB::ImageProcessor::USE_CPU);
+            SG_LOG(SG_IO, SG_ALERT, "Created nvtt mipmaps DDS for " + absFileName);
+        }
+        else {
+            simgear::effect::MipMapTuple mipmapFunctions(simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE, simgear::effect::AVERAGE);
+            srcImage1 = simgear::effect::computeMipmap(srcImage1, mipmapFunctions);
+            SG_LOG(SG_IO, SG_ALERT, "Created sg mipmaps DDS for " + absFileName);
+        }
+    }
 
     if (res.loadedFromCache())
         SG_LOG(SG_IO, SG_BULK, "Returning cached image \""
@@ -449,19 +755,21 @@ ModelRegistry::readImage(const string& fileName,
 }
 
 
-osg::Node* DefaultCachePolicy::find(const string& fileName,
-                                    const Options* opt)
+osg::ref_ptr<osg::Node> DefaultCachePolicy::find(const string& fileName, const Options* opt)
 {
     Registry* registry = Registry::instance();
-    osg::Node* cached
-        = dynamic_cast<Node*>(registry->getFromObjectCache(fileName));
-    if (cached)
-        SG_LOG(SG_IO, SG_BULK, "Got cached model \""
-               << fileName << "\"");
+#if OSG_VERSION_LESS_THAN(3,4,0)
+    osg::ref_ptr<osg::Object> cachedObject = registry->getFromObjectCache(fileName);
+#else
+    osg::ref_ptr<osg::Object> cachedObject = registry->getRefFromObjectCache(fileName);
+#endif
+
+    ref_ptr<osg::Node> cachedNode = dynamic_cast<osg::Node*>(cachedObject.get());
+    if (cachedNode.valid())
+        SG_LOG(SG_IO, SG_BULK, "Got cached model \"" << fileName << "\"");
     else
-        SG_LOG(SG_IO, SG_BULK, "Reading model \""
-               << fileName << "\"");
-    return cached;
+        SG_LOG(SG_IO, SG_BULK, "Reading model \"" << fileName << "\"");
+    return cachedNode;
 }
 
 void DefaultCachePolicy::addToCache(const string& fileName,
diff --git a/simgear/scene/model/ModelRegistry.hxx b/simgear/scene/model/ModelRegistry.hxx
index 8c8e7467..197bb197 100644
--- a/simgear/scene/model/ModelRegistry.hxx
+++ b/simgear/scene/model/ModelRegistry.hxx
@@ -132,7 +132,7 @@ struct DefaultProcessPolicy {
 
 struct DefaultCachePolicy {
     DefaultCachePolicy(const std::string& extension) {}
-    osg::Node* find(const std::string& fileName,
+    osg::ref_ptr<osg::Node> find(const std::string& fileName,
                     const osgDB::Options* opt);
     void addToCache(const std::string& filename, osg::Node* node);
 };
diff --git a/simgear/scene/model/SGReaderWriterXML.cxx b/simgear/scene/model/SGReaderWriterXML.cxx
index 4c6304ac..64ad2754 100644
--- a/simgear/scene/model/SGReaderWriterXML.cxx
+++ b/simgear/scene/model/SGReaderWriterXML.cxx
@@ -56,7 +56,7 @@ using namespace std;
 using namespace simgear;
 using namespace osg;
 
-static osg::Node *
+static std::tuple<int, osg::Node *>
 sgLoad3DModel_internal(const SGPath& path,
                        const osgDB::Options* options,
                        SGPropertyNode *overlay = 0);
@@ -88,8 +88,10 @@ SGReaderWriterXML::readNode(const std::string& name,
         if (!p.exists()) {
           return ReadResult::FILE_NOT_FOUND;
         }
-        
-        result=sgLoad3DModel_internal(p, options);
+
+        static std::tuple<int, osg::Node *> retval;
+        int num_anims;
+        std::tie(num_anims, result) = sgLoad3DModel_internal(p, options);
     } catch (const sg_exception &t) {
         SG_LOG(SG_INPUT, SG_ALERT, "Failed to load model: " << t.getFormattedMessage()
           << "\n\tfrom:" << fileName);
@@ -160,13 +162,13 @@ void makeEffectAnimations(PropertyList& animation_nodes,
         SGPropertyNode* typeProp = animProp->getChild("type");
         if (!typeProp)
             continue;
-        
+
         const char* typeString = typeProp->getStringValue();
         if (!strcmp(typeString, "material")) {
             effectProp
                 = SGMaterialAnimation::makeEffectProperties(animProp);
         } else if (!strcmp(typeString, "shader")) {
-            
+
             SGPropertyNode* shaderProp = animProp->getChild("shader");
             if (!shaderProp || strcmp(shaderProp->getStringValue(), "chrome"))
                 continue;
@@ -215,7 +217,7 @@ private:
     osg::Node::NodeMask nodeMaskSet;
     osg::Node::NodeMask nodeMaskClear;
 };
-    
+
 }
 
 namespace {
@@ -229,7 +231,7 @@ namespace {
             return (typeString == "pick") || (typeString == "knob") || (typeString == "slider") || (typeString == "touch");
         }
     };
-    
+
     bool removeNamedNode(osg::Group* aGroup, const std::string& aName)
     {
         int nKids = aGroup->getNumChildren();
@@ -240,28 +242,28 @@ namespace {
                 return true;
             }
         }
-        
+
         for (int i = 0; i < nKids; i++) {
             osg::Group* childGroup = aGroup->getChild(i)->asGroup();
             if (!childGroup)
                 continue;
-            
+
             if (removeNamedNode(childGroup, aName))
                 return true;
         } // of child groups traversal
-        
+
         return false;
     }
 }
 
-static osg::Node *
+static std::tuple<int, osg::Node *>
 sgLoad3DModel_internal(const SGPath& path,
                        const osgDB::Options* dbOptions,
                        SGPropertyNode *overlay)
 {
     if (!path.exists()) {
       SG_LOG(SG_INPUT, SG_ALERT, "Failed to load file: \"" << path << "\"");
-      return NULL;
+      return std::make_tuple(0, (osg::Node *) NULL);
     }
 
     osg::ref_ptr<SGReaderWriterOptions> options;
@@ -270,19 +272,20 @@ sgLoad3DModel_internal(const SGPath& path,
     SGPath modelpath(path);
     SGPath texturepath(path);
     SGPath modelDir(modelpath.dir());
-    
+    int animationcount = 0;
+
     SGSharedPtr<SGPropertyNode> prop_root = options->getPropertyNode();
     if (!prop_root.valid())
         prop_root = new SGPropertyNode;
     // The model data appear to be only used in the topmost model
     osg::ref_ptr<SGModelData> data = options->getModelData();
     options->setModelData(0);
-    
+
     osg::ref_ptr<osg::Node> model;
     osg::ref_ptr<osg::Group> group;
     SGPropertyNode_ptr props = new SGPropertyNode;
     bool previewMode = (dbOptions->getPluginStringData("SimGear::PREVIEW") == "ON");
-    
+
     // Check for an XML wrapper
     if (modelpath.extension() == "xml") {
        try {
@@ -296,9 +299,9 @@ sgLoad3DModel_internal(const SGPath& path,
             copyProperties(overlay, props);
 
         if (previewMode && props->hasChild("nopreview")) {
-            return NULL;
+            return std::make_tuple(0, (osg::Node *) NULL);
         }
-        
+
         if (props->hasValue("/path")) {
             string modelPathStr = props->getStringValue("/path");
             modelpath = SGModelLib::findDataFile(modelPathStr, NULL, modelDir);
@@ -335,7 +338,11 @@ sgLoad3DModel_internal(const SGPath& path,
 
         options->setDatabasePath(texturepath.local8BitStr());
         osgDB::ReaderWriter::ReadResult modelResult;
+#if OSG_VERSION_LESS_THAN(3,4,0)
         modelResult = osgDB::readNodeFile(modelpath.local8BitStr(), options.get());
+#else
+        modelResult = osgDB::readRefNodeFile(modelpath.local8BitStr(), options.get());
+#endif
         if (!modelResult.validNode())
             throw sg_io_exception("Failed to load 3D model:" + modelResult.message(),
                                   modelpath);
@@ -399,9 +406,9 @@ sgLoad3DModel_internal(const SGPath& path,
 
         SGPath submodelpath;
         osg::ref_ptr<osg::Node> submodel;
-        
+
         string subPathStr = sub_props->getStringValue("path");
-        SGPath submodelPath = SGModelLib::findDataFile(subPathStr, 
+        SGPath submodelPath = SGModelLib::findDataFile(subPathStr,
           NULL, modelDir);
 
         if (submodelPath.isNull()) {
@@ -419,14 +426,16 @@ sgLoad3DModel_internal(const SGPath& path,
         }
 
         try {
-            submodel = sgLoad3DModel_internal(submodelPath, options.get(),
+            int num_anims;
+            std::tie(num_anims, submodel) = sgLoad3DModel_internal(submodelPath, options.get(),
                                               sub_props->getNode("overlay"));
+            animationcount += num_anims;
         } catch (const sg_exception &t) {
             SG_LOG(SG_INPUT, SG_ALERT, "Failed to load submodel: " << t.getFormattedMessage()
               << "\n\tfrom:" << t.getOrigin());
             continue;
         }
-        
+
         if (!submodel)
             continue;
 
@@ -481,7 +490,7 @@ sgLoad3DModel_internal(const SGPath& path,
         }
     }
 
-    if (dbOptions->getPluginStringData("SimGear::PARTICLESYSTEM") != "OFF") {
+    if (GlobalParticleCallback::getEnabled()){//dbOptions->getPluginStringData("SimGear::PARTICLESYSTEM") != "OFF") {
         std::vector<SGPropertyNode_ptr> particle_nodes;
         particle_nodes = props->getChildren("particlesystem");
         for (unsigned i = 0; i < particle_nodes.size(); ++i) {
@@ -491,7 +500,7 @@ sgLoad3DModel_internal(const SGPath& path,
             if (i==0) {
                 if (!texturepath.extension().empty())
                     texturepath = texturepath.dir();
-                
+
                 options2->setDatabasePath(texturepath.local8BitStr());
             }
             group->addChild(Particles::appendParticles(particle_nodes[i],
@@ -510,13 +519,13 @@ sgLoad3DModel_internal(const SGPath& path,
 
     PropertyList effect_nodes = props->getChildren("effect");
     PropertyList animation_nodes = props->getChildren("animation");
-    
+
     if (previewMode) {
         PropertyList::iterator it;
         it = std::remove_if(animation_nodes.begin(), animation_nodes.end(), ExcludeInPreview());
         animation_nodes.erase(it, animation_nodes.end());
     }
-    
+
     // Some material animations (eventually all) are actually effects.
     makeEffectAnimations(animation_nodes, effect_nodes);
     {
@@ -543,13 +552,15 @@ sgLoad3DModel_internal(const SGPath& path,
         /// OSGFIXME: duh, why not only model?????
         SGAnimation::animate(modelData);
     }
-    
+
+    animationcount += animation_nodes.size();
+
     if (!needTransform && group->getNumChildren() < 2) {
         model = group->getChild(0);
         group->removeChild(model.get());
         if (data.valid())
             data->modelLoaded(modelpath.utf8Str(), props, model.get());
-        return model.release();
+        return std::make_tuple(animationcount, model.release());
     }
     if (data.valid())
         data->modelLoaded(modelpath.utf8Str(), props, group.get());
@@ -559,6 +570,7 @@ sgLoad3DModel_internal(const SGPath& path,
         osgDB::writeNodeFile(*group, outputfile);
     }
 
-    return group.release();
-}
+    SG_LOG(SG_GENERAL, SG_DEBUG, "Model " << path << " animation count: " << animationcount);
 
+    return std::make_tuple(animationcount, group.release());
+}
diff --git a/simgear/scene/model/model.cxx b/simgear/scene/model/model.cxx
index 6b34ea9c..737c7597 100644
--- a/simgear/scene/model/model.cxx
+++ b/simgear/scene/model/model.cxx
@@ -43,9 +43,18 @@ SGLoadTexture2D(bool staticTexture, const std::string& path,
 {
   osg::Image* image;
   if (options)
-    image = osgDB::readImageFile(path, options);
+#if OSG_VERSION_LESS_THAN(3,4,0)
+      image = osgDB::readImageFile(path, options);
+#else
+      image = osgDB::readRefImageFile(path, options);
+#endif
   else
-    image = osgDB::readImageFile(path);
+#if OSG_VERSION_LESS_THAN(3,4,0)
+      image = osgDB::readImageFile(path);
+#else
+      image = osgDB::readRefImageFile(path);
+#endif
+
   osg::ref_ptr<osg::Texture2D> texture = new osg::Texture2D;
   texture->setImage(image);
   if (staticTexture)
@@ -141,7 +150,11 @@ Texture2D* TextureUpdateVisitor::textureReplace(int unit, const StateAttribute*
     // If it is empty or they are identical then there is nothing to do
     if (fullLiveryFile.empty() || fullLiveryFile == *fullFilePath)
         return 0;
+#if OSG_VERSION_LESS_THAN(3,4,0)
     Image* newImage = readImageFile(fullLiveryFile);
+#else
+    Image* newImage = readRefImageFile(fullLiveryFile);
+#endif
     if (!newImage)
         return 0;
     CopyOp copyOp(CopyOp::DEEP_COPY_ALL & ~CopyOp::DEEP_COPY_IMAGES);
diff --git a/simgear/scene/model/modellib.cxx b/simgear/scene/model/modellib.cxx
index 7ce382d3..d11e0d21 100644
--- a/simgear/scene/model/modellib.cxx
+++ b/simgear/scene/model/modellib.cxx
@@ -101,7 +101,11 @@ osg::Node* loadFile(const string& path, SGReaderWriterOptions* options)
         options->setInstantiateEffects(true);
     }
 
+#if OSG_VERSION_LESS_THAN(3,4,0)
+    ref_ptr<Node> model = readNodeFile(path, options);
+#else
     ref_ptr<Node> model = readRefNodeFile(path, options);
+#endif
     if (!model)
         return 0;
     else
diff --git a/simgear/scene/sky/cloud.cxx b/simgear/scene/sky/cloud.cxx
index 3c03c514..89a964b7 100644
--- a/simgear/scene/sky/cloud.cxx
+++ b/simgear/scene/sky/cloud.cxx
@@ -485,9 +485,11 @@ SGCloudLayer::rebuild()
 // repaint the cloud layer colors
 bool SGCloudLayer::repaint( const SGVec3f& fog_color ) {
     osg::Vec4f combineColor(toOsg(fog_color), cloud_alpha);
-    osg::TexEnvCombine* combiner
-        = dynamic_cast<osg::TexEnvCombine*>(layer_root->getStateSet()
-                                            ->getTextureAttribute(1, osg::StateAttribute::TEXENV));
+    osg::StateAttribute* textureAtt = layer_root->getStateSet()->getTextureAttribute(1, osg::StateAttribute::TEXENV);
+    osg::TexEnvCombine* combiner = dynamic_cast<osg::TexEnvCombine*>(textureAtt);
+
+    if (combiner == nullptr)
+        return false;
     combiner->setConstantColor(combineColor);
 
     // Set the fog color for the 3D clouds too.
diff --git a/simgear/scene/tgdb/ReaderWriterSPT.cxx b/simgear/scene/tgdb/ReaderWriterSPT.cxx
index cb6f4df1..66fad24b 100644
--- a/simgear/scene/tgdb/ReaderWriterSPT.cxx
+++ b/simgear/scene/tgdb/ReaderWriterSPT.cxx
@@ -208,7 +208,11 @@ ReaderWriterSPT::readObject(const std::string& fileName, const osgDB::Options* o
         imageFileName = osgDB::concatPaths(imageFileName, "Globe");
         imageFileName = osgDB::concatPaths(imageFileName, "world.topo.bathy.200407.3x4096x2048.png");
     }
+#if OSG_VERSION_LESS_THAN(3,4,0)
     if (osg::Image* image = osgDB::readImageFile(imageFileName, options)) {
+#else
+    if (osg::Image* image = osgDB::readRefImageFile(imageFileName, options)) {
+#endif
         osg::Texture2D* texture = new osg::Texture2D;
         texture->setImage(image);
         texture->setWrap(osg::Texture2D::WRAP_S, osg::Texture2D::REPEAT);
@@ -256,7 +260,11 @@ ReaderWriterSPT::createTree(const BucketBox& bucketBox, const LocalOptions& opti
     if (bucketBox.getIsBucketSize()) {
         std::string fileName;
         fileName = bucketBox.getBucket().gen_index_str() + std::string(".stg");
+#if OSG_VERSION_LESS_THAN(3,4,0)
+        return osgDB::readNodeFile(fileName, options._options);
+#else
         return osgDB::readRefNodeFile(fileName, options._options);
+#endif
     } else if (!topLevel && options.isPageLevel(bucketBox.getStartLevel())) {
         return createPagedLOD(bucketBox, options);
     } else {
@@ -314,7 +322,11 @@ ReaderWriterSPT::createPagedLOD(const BucketBox& bucketBox, const LocalOptions&
         std::string fileName = osgDB::findDataFile(lodPath + extensions[i], options._options);
         if (fileName.empty())
             continue;
+#if OSG_VERSION_LESS_THAN(3,4,0)
+        osg::ref_ptr<osg::Node> node = osgDB::readNodeFile(fileName, options._options);
+#else
         osg::ref_ptr<osg::Node> node = osgDB::readRefNodeFile(fileName, options._options);
+#endif
         if (!node.valid())
             continue;
         pagedLOD->addChild(node.get(), range, std::numeric_limits<float>::max());
@@ -412,7 +424,11 @@ ReaderWriterSPT::getLowLODStateSet(const LocalOptions& options) const
     localOptions = static_cast<osgDB::Options*>(options._options->clone(osg::CopyOp()));
     localOptions->setObjectCacheHint(osgDB::Options::CACHE_ALL);
 
+#if OSG_VERSION_LESS_THAN(3,4,0)
+    osg::ref_ptr<osg::Object> object = osgDB::readObjectFile("state.spt", localOptions.get());
+#else
     osg::ref_ptr<osg::Object> object = osgDB::readRefObjectFile("state.spt", localOptions.get());
+#endif
     if (!dynamic_cast<osg::StateSet*>(object.get()))
         return 0;
 
diff --git a/simgear/scene/tgdb/ReaderWriterSTG.cxx b/simgear/scene/tgdb/ReaderWriterSTG.cxx
index 46f73ba9..4a3887a4 100644
--- a/simgear/scene/tgdb/ReaderWriterSTG.cxx
+++ b/simgear/scene/tgdb/ReaderWriterSTG.cxx
@@ -156,7 +156,11 @@ struct ReaderWriterSTG::_ModelBin {
                 proxy->setCenterMode(osg::ProxyNode::UNION_OF_BOUNDING_SPHERE_AND_USER_DEFINED);
                 node = proxy;
             } else {
+#if OSG_VERSION_LESS_THAN(3,4,0)
+                node = osgDB::readNodeFile(o._name, o._options.get());
+#else
                 node = osgDB::readRefNodeFile(o._name, o._options.get());
+#endif
                 if (!node.valid()) {
                     SG_LOG(SG_TERRAIN, SG_ALERT, o._errorLocation << ": Failed to load "
                            << o._token << " '" << o._name << "'");
@@ -553,7 +557,11 @@ struct ReaderWriterSTG::_ModelBin {
         if (_foundBase) {
             for (auto stgObject : _objectList) {
                 osg::ref_ptr<osg::Node> node;
+#if OSG_VERSION_LESS_THAN(3,4,0)
+                node = osgDB::readNodeFile(stgObject._name, stgObject._options.get());
+#else
                 node = osgDB::readRefNodeFile(stgObject._name, stgObject._options.get());
+#endif
                 if (!node.valid()) {
                     SG_LOG(SG_TERRAIN, SG_ALERT, stgObject._errorLocation << ": Failed to load "
                            << stgObject._token << " '" << stgObject._name << "'");
@@ -586,7 +594,7 @@ struct ReaderWriterSTG::_ModelBin {
             i->_elev += elevation(*terrainGroup, SGGeod::fromDeg(i->_lon, i->_lat));
         }
 
-        if (_objectStaticList.empty() && _signList.empty()) {
+        if (_objectStaticList.empty() && _signList.empty() && (_buildingListList.size() == 0)) {
             // The simple case, just return the terrain group
             return terrainGroup.release();
         } else {
diff --git a/simgear/scene/tgdb/SGTileDetailsCallback.hxx b/simgear/scene/tgdb/SGTileDetailsCallback.hxx
index e7612c68..6a16c5da 100644
--- a/simgear/scene/tgdb/SGTileDetailsCallback.hxx
+++ b/simgear/scene/tgdb/SGTileDetailsCallback.hxx
@@ -689,10 +689,13 @@ public:
                 triangleBuildingList.clear();
             }
             
-            SG_LOG(SG_TERRAIN, SG_DEBUG, "Random Buildings: " << ((bin) ? bin->getNumBuildings() : 0));
-            SG_LOG(SG_TERRAIN, SG_DEBUG, "  Dropped due to mask: " << mask_dropped);
-            SG_LOG(SG_TERRAIN, SG_DEBUG, "  Dropped due to random object: " << random_dropped);
-            SG_LOG(SG_TERRAIN, SG_DEBUG, "  Dropped due to other buildings: " << building_dropped);
+            const int numBuildings = (bin) ? bin->getNumBuildings() : 0;
+            if (numBuildings > 0) {
+                SG_LOG(SG_TERRAIN, SG_DEBUG, "computed Random Buildings: " << numBuildings);
+                SG_LOG(SG_TERRAIN, SG_DEBUG, "  Dropped due to mask: " << mask_dropped);
+                SG_LOG(SG_TERRAIN, SG_DEBUG, "  Dropped due to random object: " << random_dropped);
+                SG_LOG(SG_TERRAIN, SG_DEBUG, "  Dropped due to other buildings: " << building_dropped);
+            }
         }
     }
     
diff --git a/simgear/scene/util/SGReaderWriterOptions.hxx b/simgear/scene/util/SGReaderWriterOptions.hxx
index 2760df90..17183944 100644
--- a/simgear/scene/util/SGReaderWriterOptions.hxx
+++ b/simgear/scene/util/SGReaderWriterOptions.hxx
@@ -38,12 +38,22 @@ namespace simgear
 
 class SGReaderWriterOptions : public osgDB::Options {
 public:
+    enum LoadOriginHint
+    {
+        ORIGIN_MODEL,
+        ORIGIN_EFFECTS,
+        ORIGIN_EFFECTS_NORMALIZED,
+    };
+
+    //SGReaderWriterOptions* cloneOptions(const osg::CopyOp& copyop = osg::CopyOp::SHALLOW_COPY) const { return static_cast<SGReaderWriterOptions*>(clone(copyop)); }
+
     SGReaderWriterOptions() :
         _materialLib(0),
         _load_panel(0),
         _model_data(0),
         _instantiateEffects(false),
-        _instantiateMaterialEffects(false)
+        _instantiateMaterialEffects(false),
+        _LoadOriginHint(ORIGIN_MODEL)
     { }
     SGReaderWriterOptions(const std::string& str) :
         osgDB::Options(str),
@@ -51,7 +61,8 @@ public:
         _load_panel(0),
         _model_data(0),
         _instantiateEffects(false),
-        _instantiateMaterialEffects(false)
+        _instantiateMaterialEffects(false),
+        _LoadOriginHint(ORIGIN_MODEL)
     { }
     SGReaderWriterOptions(const osgDB::Options& options,
                           const osg::CopyOp& copyop = osg::CopyOp::SHALLOW_COPY) :
@@ -60,7 +71,8 @@ public:
         _load_panel(0),
         _model_data(0),
         _instantiateEffects(false),
-        _instantiateMaterialEffects(false)
+        _instantiateMaterialEffects(false),
+        _LoadOriginHint(ORIGIN_MODEL)
     { }
     SGReaderWriterOptions(const SGReaderWriterOptions& options,
                           const osg::CopyOp& copyop = osg::CopyOp::SHALLOW_COPY) :
@@ -75,7 +87,8 @@ public:
         _instantiateEffects(options._instantiateEffects),
         _instantiateMaterialEffects(options._instantiateMaterialEffects),
         _materialName(options._materialName),
-        _sceneryPathSuffixes(options._sceneryPathSuffixes)
+        _sceneryPathSuffixes(options._sceneryPathSuffixes),
+        _LoadOriginHint(ORIGIN_MODEL)
     { }
 
     META_Object(simgear, SGReaderWriterOptions);
@@ -139,6 +152,13 @@ public:
     const SGGeod& getLocation() const
     { return _geod; }
 
+    // the load origin defines where the load request has come from.
+    // example usage; to allow the DDS Texture Cache (DTC) to ignore 
+    // any texture that is used in a shader, as these often have special values
+    // encoded into the channels that aren't suitable for conversion.
+    void setLoadOriginHint(LoadOriginHint _v) const { _LoadOriginHint = _v; } 
+    LoadOriginHint getLoadOriginHint() const { return _LoadOriginHint; } 
+
 protected:
     virtual ~SGReaderWriterOptions();
 
@@ -157,6 +177,7 @@ private:
     string _materialName;
     string_list _sceneryPathSuffixes;
     SGGeod _geod;
+    mutable LoadOriginHint _LoadOriginHint;
 };
 
 }
diff --git a/simgear/scene/util/SGSceneFeatures.cxx b/simgear/scene/util/SGSceneFeatures.cxx
index a3549a80..48aecf22 100644
--- a/simgear/scene/util/SGSceneFeatures.cxx
+++ b/simgear/scene/util/SGSceneFeatures.cxx
@@ -40,14 +40,14 @@
 
 SGSceneFeatures::SGSceneFeatures() :
   _textureCompression(UseARBCompression),
-  _shaderLights(true),
-  _pointSpriteLights(true),
-  _distanceAttenuationLights(true),
-  _textureFilter(1),
   _MaxTextureSize(4096),
   _TextureCacheCompressionActive(true),
   _TextureCacheCompressionActiveTransparent(true),
-  _TextureCacheActive(false)
+  _TextureCacheActive(false),
+  _shaderLights(true),
+  _pointSpriteLights(true),
+  _distanceAttenuationLights(true),
+  _textureFilter(1)
 {
 }
 
diff --git a/simgear/simgear_config_cmake.h.in b/simgear/simgear_config_cmake.h.in
index de1b69c6..89492869 100644
--- a/simgear/simgear_config_cmake.h.in
+++ b/simgear/simgear_config_cmake.h.in
@@ -27,4 +27,5 @@
 #cmakedefine ENABLE_SOUND
 #cmakedefine USE_AEONWAVE
 #cmakedefine ENABLE_SIMD
+#cmakedefine ENABLE_SIMD_CODE
 #cmakedefine ENABLE_GDAL
diff --git a/simgear/sound/readwav.cxx b/simgear/sound/readwav.cxx
index 005cf193..d5c16cd2 100644
--- a/simgear/sound/readwav.cxx
+++ b/simgear/sound/readwav.cxx
@@ -65,16 +65,16 @@ namespace
       else if (numChannels == 2 && bitsPerSample == 16) rv = SG_SAMPLE_STEREO16;
       else if (numChannels == 2 && bitsPerSample == 8) rv = SG_SAMPLE_STEREO8;
       else {
-        char msg[65];
-        snprintf(msg, 64, "Unsupported audio format: tracks: %i, bits/sample: %i", numChannels, bitsPerSample);
+        char msg[81];
+        snprintf(msg, 80, "Unsupported audio format: tracks: %i, bits/sample: %i", numChannels, bitsPerSample);
         throw sg_exception(msg);
       }
     } else {
       if (numChannels == 1 && bitsPerSample == 4) rv = SG_SAMPLE_ADPCM; 
       else if (numChannels == 1 && bitsPerSample == 8) rv = SG_SAMPLE_MULAW;
       else {
-        char msg[65];
-        snprintf(msg, 64, "Unsupported compressed audio format: tracks: %i, bits/sample: %i", numChannels, bitsPerSample);
+        char msg[81];
+        snprintf(msg, 80, "Unsupported compressed audio format: tracks: %i, bits/sample: %i", numChannels, bitsPerSample);
         throw sg_exception(msg);
       }
     }
diff --git a/simgear/sound/soundmgr_aeonwave.cxx b/simgear/sound/soundmgr_aeonwave.cxx
index b25fe008..111fa10e 100644
--- a/simgear/sound/soundmgr_aeonwave.cxx
+++ b/simgear/sound/soundmgr_aeonwave.cxx
@@ -8,7 +8,7 @@
 // Modified for the new SoundSystem by Erik Hofman, October 2009
 //
 // Copyright (C) 2001  Curtis L. Olson - http://www.flightgear.org/~curt
-// Copyright (C) 2009 Erik Hofman <erik@ehofman.com>
+// Copyright (C) 2009-2019 Erik Hofman <erik@ehofman.com>
 //
 // This program is free software; you can redistribute it and/or
 // modify it under the terms of the GNU General Public License as
@@ -418,8 +418,8 @@ void SGSoundMgr::release_source( unsigned int source )
     {
         aax::Emitter& emitter = source_it->second;
         enum aaxState state = emitter.state();
-        if (state == AAX_PLAYING || state == AAX_SUSPENDED) {
-           TRY( emitter.set(AAX_STOPPED) );
+        if (state != AAX_PROCESSED) {
+           TRY( emitter.set(AAX_PROCESSED) );
            TRY( d->_aax.remove(emitter) );
         }
         TRY( emitter.remove_buffer() );
@@ -555,7 +555,6 @@ void SGSoundMgr::sample_play( SGSoundSample *sample )
         if (bufid == SGSoundMgr::FAILED_BUFFER ||
             bufid == SGSoundMgr::NO_BUFFER)
         {
-printf("A: release: %i, bufid: %i (%i, %i)\n", sample->get_source(), bufid, SGSoundMgr::FAILED_BUFFER, SGSoundMgr::NO_BUFFER);
             release_source(sample->get_source());
             return;
         }
@@ -590,8 +589,7 @@ void SGSoundMgr::sample_stop( SGSoundSample *sample )
         if ( sample->is_looping() && !stopped) {
 #ifdef ENABLE_SOUND
             aax::Emitter& emitter = d->get_emitter(source);
-            TRY( emitter.set(AAX_STOPPED) );
-            TRY( d->_aax.remove(emitter) );
+            TRY( emitter.set(AAX_PROCESSED) );
 #endif          
             stopped = is_sample_stopped(sample);
         }
@@ -610,8 +608,7 @@ void SGSoundMgr::sample_destroy( SGSoundSample *sample )
         unsigned int source = sample->get_source();
         if ( sample->is_playing() ) {
             aax::Emitter& emitter = d->get_emitter(source);
-            TRY( emitter.set(AAX_STOPPED) );
-            TRY( d->_aax.remove(emitter) );
+            TRY( emitter.set(AAX_PROCESSED) );
         }
         release_source( source );
 #endif
diff --git a/simgear/structure/subsystem_mgr.cxx b/simgear/structure/subsystem_mgr.cxx
index a7294f5f..fc29e883 100644
--- a/simgear/structure/subsystem_mgr.cxx
+++ b/simgear/structure/subsystem_mgr.cxx
@@ -281,7 +281,7 @@ SGSubsystemGroup::incrementalInit()
         notifyDidChange(m->subsystem, State::INIT);
         ++_initPosition;
         
-        if (_initPosition < _members.size()) {
+        if (_initPosition < static_cast<int>(_members.size())) {
             // start init of the next one
             notifyWillChange( _members[_initPosition]->subsystem, State::INIT);
         }
diff --git a/simgear/timing/timestamp.cxx b/simgear/timing/timestamp.cxx
index 7553d322..067a1b95 100644
--- a/simgear/timing/timestamp.cxx
+++ b/simgear/timing/timestamp.cxx
@@ -72,13 +72,33 @@ static clockid_t getClockId()
 
 #endif
 
+#ifdef _WIN32
+static bool qpc_init = false;
+static LARGE_INTEGER s_frequency;
+static BOOL s_use_qpc;
+#endif
+
 void SGTimeStamp::stamp()
 {
 #ifdef _WIN32
-    unsigned int t;
-    t = timeGetTime();
-    _sec = t / 1000;
-    _nsec = ( t - ( _sec * 1000 ) ) * 1000 * 1000;
+    if (!qpc_init) {
+        s_use_qpc = QueryPerformanceFrequency(&s_frequency);
+        qpc_init = true;
+    }
+    if (qpc_init && s_use_qpc) {
+        LARGE_INTEGER now;
+        QueryPerformanceCounter(&now);
+        _sec = now.QuadPart / s_frequency.QuadPart;
+        _nsec = (1000000000LL * (now.QuadPart - _sec * s_frequency.QuadPart)) / s_frequency.QuadPart;
+    }
+    else {
+        unsigned int t;
+
+        t = timeGetTime();
+        _sec = t / 1000;
+        _nsec = (t - (_sec * 1000)) * 1000 * 1000;
+    }
+
 #elif defined(_POSIX_TIMERS) && (0 < _POSIX_TIMERS)
     struct timespec ts;
     clock_gettime(getClockId(), &ts);