From d8cfc9b1f5fd77cf82e8f9cd677ff4406a9ad476 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Fri, 26 Sep 2008 15:47:31 +0000
Subject: [PATCH] Improved GLSL isosurface support when using a transfer
 function

---
 examples/osgvolume/osgvolume.cpp          |  8 +++++---
 examples/osgvolume/volume_tf_iso_frag.cpp | 21 ++++++++++++++++++---
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/examples/osgvolume/osgvolume.cpp b/examples/osgvolume/osgvolume.cpp
index 2e124b143..b34ccc72c 100644
--- a/examples/osgvolume/osgvolume.cpp
+++ b/examples/osgvolume/osgvolume.cpp
@@ -876,6 +876,9 @@ osg::Node* createShaderModel(ShadingModel shadingModel,
         texture3D->setImage(image_3d.get());
 
         stateset->setTextureAttributeAndModes(0,texture3D,osg::StateAttribute::ON);
+
+        osg::Uniform* baseTextureSampler = new osg::Uniform("baseTexture",0);
+        stateset->addUniform(baseTextureSampler);
     }
     
 
@@ -943,7 +946,7 @@ osg::Node* createShaderModel(ShadingModel shadingModel,
             texture1D->setWrap(osg::Texture::WRAP_R,osg::Texture::CLAMP_TO_EDGE);
             stateset->setTextureAttributeAndModes(0,texture1D,osg::StateAttribute::ON);
 
-            osg::Shader* fragmentShader = osgDB::readShaderFile(osg::Shader::FRAGMENT, "volume-tf-iso.frag");
+            osg::Shader* fragmentShader = osgDB::readShaderFile(osg::Shader::FRAGMENT, "volume_tf_iso.frag");
             if (fragmentShader)
             {
                 program->addShader(fragmentShader);
@@ -1056,6 +1059,7 @@ osg::Node* createShaderModel(ShadingModel shadingModel,
     }
     else
     {    
+
         osg::Shader* fragmentShader = osgDB::readShaderFile(osg::Shader::FRAGMENT, "volume.frag");
         if (fragmentShader)
         {
@@ -1067,8 +1071,6 @@ osg::Node* createShaderModel(ShadingModel shadingModel,
             program->addShader(new osg::Shader(osg::Shader::FRAGMENT, volume_frag));
         }
     }
-    osg::Uniform* baseTextureSampler = new osg::Uniform("baseTexture",0);
-    stateset->addUniform(baseTextureSampler);
 
     osg::Uniform* sampleDensity = new osg::Uniform("sampleDensity", 0.01f);
     stateset->addUniform(sampleDensity);
diff --git a/examples/osgvolume/volume_tf_iso_frag.cpp b/examples/osgvolume/volume_tf_iso_frag.cpp
index ada3e14b3..3453f03d4 100644
--- a/examples/osgvolume/volume_tf_iso_frag.cpp
+++ b/examples/osgvolume/volume_tf_iso_frag.cpp
@@ -1,4 +1,4 @@
-char volume_tf_iso_frag[] = "uniform sampler3D baseTexture;\n"
+char volume_tf_iso_frag[] = "uniform sampler3D normalMap;\n"
                             "uniform sampler1D tfTexture;\n"
                             "uniform float sampleDensity;\n"
                             "uniform float transparency;\n"
@@ -13,6 +13,8 @@ char volume_tf_iso_frag[] = "uniform sampler3D baseTexture;\n"
                             "    vec3 t0 = (texgen * vertexPos).xyz;\n"
                             "    vec3 te = (texgen * cameraPos).xyz;\n"
                             "\n"
+                            "    vec3 eyeDirection = normalize(te-t0);\n"
+                            "\n"
                             "    if (te.x>=0.0 && te.x<=1.0 &&\n"
                             "        te.y>=0.0 && te.y<=1.0 &&\n"
                             "        te.z>=0.0 && te.z<=1.0)\n"
@@ -73,12 +75,25 @@ char volume_tf_iso_frag[] = "uniform sampler3D baseTexture;\n"
                             "    vec4 fragColor = vec4(0.0, 0.0, 0.0, 0.0); \n"
                             "    while(num_iterations>0.0)\n"
                             "    {\n"
-                            "        float v = texture3D( baseTexture, texcoord).s;\n"
+                            "        vec4 normal = texture3D( normalMap, texcoord);\n"
+                            "        float v = normal.w;\n"
                             "        vec4 color = texture1D( tfTexture, v);\n"
-                            "        if (alphaCutOff<color.w)\n"
+                            "\n"
+                            "        normal.x = normal.x*2.0-1.0;\n"
+                            "        normal.y = normal.y*2.0-1.0;\n"
+                            "        normal.z = normal.z*2.0-1.0;\n"
+                            "        \n"
+                            "        float lightScale = 0.1 +  max(dot(normal.xyz, eyeDirection), 0.0);\n"
+                            "        color.x *= lightScale;\n"
+                            "        color.y *= lightScale;\n"
+                            "        color.z *= lightScale;\n"
+                            "        color.w = 1.0;\n"
+                            "    \n"
+                            "        if (v>=alphaCutOff)\n"
                             "        {\n"
                             "            fragColor = color;\n"
                             "        }\n"
+                            "\n"
                             "        texcoord += deltaTexCoord; \n"
                             "\n"
                             "        --num_iterations;\n"