Added support for min to max level ranges for Layers in support of VirtualPlanetBuilder usage of this.

src/osgPlugins/osgTerrain/Terrain.cpp

@@ -185,6 +185,18 @@ osgTerrain::Layer* readLayer(osgDB::Input& fr, bool& itrAdvanced)
         itrAdvanced = true;
     }
         
+    unsigned int minLevel=0;
+    if (fr.read("MinLevel",minLevel))
+    {
+        itrAdvanced = true;
+    }
+
+    unsigned int maxLevel = MAXIMUM_NUMBER_OF_LEVELS;
+    if (fr.read("MaxLevel",maxLevel))
+    {
+        itrAdvanced = true;
+    }
+
 
     if (fr.matchSequence("CompositeLayer {"))
     {
@@ -291,6 +303,9 @@ osgTerrain::Layer* readLayer(osgDB::Input& fr, bool& itrAdvanced)
         layer->setLocator(locator.get());
     }
     
+    layer->setMinLevel(minLevel);
+    layer->setMaxLevel(maxLevel);
+    
     return layer.release();
 }
 
@@ -554,6 +569,16 @@ bool writeLayer(const osgTerrain::Layer& layer, osgDB::Output& fw)
         writeLocator(*layer.getLocator(),fw);
     }
 
+    if (layer.getMinLevel()!=0)
+    {
+        fw.indent()<<"MinLevel "<<layer.getMinLevel()<<std::endl;
+    } 
+
+    if (layer.getMinLevel()!=MAXIMUM_NUMBER_OF_LEVELS)
+    {
+        fw.indent()<<"MaxLevel "<<layer.getMaxLevel()<<std::endl;
+    } 
+
     const osgTerrain::ProxyLayer* proxyLayer = dynamic_cast<const osgTerrain::ProxyLayer*>(&layer);
     if (proxyLayer)
     {

src/osgTerrain/Layer.cpp

@@ -16,13 +16,17 @@
 
 using namespace osgTerrain;
 
-Layer::Layer()
+Layer::Layer():
+    _minLevel(0),
+    _maxLevel(MAXIMUM_NUMBER_OF_LEVELS)
 {
 }
 
 Layer::Layer(const Layer& layer,const osg::CopyOp& copyop):
     osg::Object(layer,copyop),
-    _filename(layer._filename)
+    _filename(layer._filename),
+    _minLevel(layer._minLevel),
+    _maxLevel(layer._maxLevel)
 {
 }