Removed hardware down sampling hack from GeoemtryTechnique and replaced with Terrain::g/setSampleRatio()

usage.

examples/osgmultitexturecontrol/osgmultitexturecontrol.cpp

@@ -259,6 +259,7 @@ int main( int argc, char **argv )
         {
             terrain = new osgTerrain::Terrain;
             terrain->addChild(rootnode);
+            terrain->setSampleRatio(0.25f);
 
             rootnode = terrain;
         }    

include/osgTerrain/Terrain

@@ -36,6 +36,14 @@ class OSGTERRAIN_EXPORT Terrain : public osg::Group
 
         virtual void traverse(osg::NodeVisitor& nv);
         
+        /** Set the sample ratio hint that TerrainTile should use when building geometry.
+          * Defaults to 1.0, which means use all original sample points.*/
+        void setSampleRatio(float ratio) { _sampleRatio  = ratio; }
+
+        /** Get the sample ratio hint.*/
+        float getSampleRatio() const { return _sampleRatio; }
+        
+        
         /** Get the TerrainTile for a given TileID.*/
         TerrainTile* getTile(const TileID& tileID);
 
@@ -54,10 +62,11 @@ class OSGTERRAIN_EXPORT Terrain : public osg::Group
         typedef std::map< TileID, TerrainTile* >    TerrainTileMap;
         typedef std::set< TerrainTile* >            TerrainTileSet;
 
+        float                               _sampleRatio;
+
         mutable OpenThreads::Mutex          _mutex;
         TerrainTileSet                      _terrainTileSet;
         TerrainTileMap                      _terrainTileMap;
-        
 
        
 };

src/osgTerrain/GeometryTechnique.cpp

@@ -13,6 +13,7 @@
 
 #include <osgTerrain/GeometryTechnique>
 #include <osgTerrain/TerrainTile>
+#include <osgTerrain/Terrain>
 
 #include <osgUtil/SmoothingVisitor>
 
@@ -228,23 +229,25 @@ void GeometryTechnique::generateGeometry(Locator* masterLocator, const osg::Vec3
         numRows = elevationLayer->getNumRows();
     }
     
+    float sampleRatio = _terrainTile->getTerrain() ? _terrainTile->getTerrain()->getSampleRatio() : 1.0f;
     
     double i_sampleFactor = 1.0;
     double j_sampleFactor = 1.0;
 
-    unsigned int targetSize = 32;
-    if (numColumns==64 && numColumns>targetSize)
+    if (sampleRatio!=1.0f)
     {
+    
         unsigned int originalNumColumns = numColumns;
         unsigned int originalNumRows = numRows;
     
-        numColumns = targetSize;
-        numRows = targetSize;
+        numColumns = std::max((unsigned int) (float(originalNumColumns)*sqrtf(sampleRatio)), 4u);
+        numRows = std::max((unsigned int) (float(originalNumRows)*sqrtf(sampleRatio)),4u);
 
         i_sampleFactor = double(originalNumColumns-1)/double(numColumns-1);
         j_sampleFactor = double(originalNumRows-1)/double(numRows-1);
     }
     
+    
 
     bool treatBoundariesToValidDataAsDefaultValue = _terrainTile->getTreatBoundariesToValidDataAsDefaultValue();
     osg::notify(osg::INFO)<<"TreatBoundariesToValidDataAsDefaultValue="<<treatBoundariesToValidDataAsDefaultValue<<std::endl;

src/osgTerrain/Terrain.cpp

@@ -17,12 +17,14 @@
 using namespace osg;
 using namespace osgTerrain;
 
-Terrain::Terrain()
+Terrain::Terrain():
+    _sampleRatio(1.0)
 {
 }
 
 Terrain::Terrain(const Terrain& ts, const osg::CopyOp& copyop):
-    osg::Group(ts,copyop)
+    osg::Group(ts,copyop),
+    _sampleRatio(ts._sampleRatio)
 {
 }