Fixed DrawCallback in Drawable and added CullCallback to Drawable

Cull Visitor now checks for a Drawable's CullCallback and calls it
if it exists.  It then prunes based on the return value (bool) of the
cull callback.

include/osg/Drawable

@@ -10,6 +10,7 @@
 #include <osg/State>
 #include <osg/Types>
 #include <osg/Vec2>
+#include <osg/NodeVisitor>
 
 #include <vector>
 #include <map>
@@ -168,7 +169,7 @@ class SG_EXPORT Drawable : public Object
         struct DrawCallback : public osg::Referenced
         {
                 /** do customized draw code.*/
-                virtual void drawImmediateMode(State& state,osg::Drawable* drawable) const;
+                virtual void drawImmediateMode(State& state,osg::Drawable* drawable) const = 0;
         };
         
         friend struct osg::Drawable::DrawCallback;
@@ -182,6 +183,23 @@ class SG_EXPORT Drawable : public Object
         /** Get the const ComputerTransfromCallback.*/
         const DrawCallback* getDrawCallback() const { return _drawCallback.get(); }
 
+        struct CullCallback : public osg::Referenced
+        {
+                /** do customized cull code.*/
+                virtual bool cull(osg::NodeVisitor *visitor, osg::Drawable* drawable) = 0;
+        };
+        
+        friend struct osg::Drawable::CullCallback;
+
+        /** Set the CullCallback which allows users to attach customize the drawing of existing Drawable object.*/
+        void setCullCallback(CullCallback* cc) { _cullCallback=cc; }
+        
+        /** Get the non const ComputerTransfromCallback.*/
+        CullCallback* getCullCallback() { return _cullCallback.get(); }
+        
+        /** Get the const ComputerTransfromCallback.*/
+        const CullCallback* getCullCallback() const { return _cullCallback.get(); }
+
 
         /** draw directly ignoring an OpenGL display list which could be attached.
           * This is the internal draw method which does the drawing itself,
@@ -277,6 +295,7 @@ class SG_EXPORT Drawable : public Object
         mutable bool            _bbox_computed;
         
         ref_ptr<DrawCallback>   _drawCallback;
+        ref_ptr<CullCallback>   _cullCallback;
         
         // static cache of deleted display lists which can only 
         // by completely deleted once the appropriate OpenGL context

src/osg/Drawable.cpp

@@ -38,7 +38,8 @@ Drawable::Drawable(const Drawable& drawable,const CopyOp& copyop):
     _globjList(drawable._globjList),
     _bbox(drawable._bbox),
     _bbox_computed(drawable._bbox_computed),
-    _drawCallback(drawable._drawCallback)
+    _drawCallback(drawable._drawCallback),
+    _cullCallback(drawable._cullCallback)
 {}
 
 Drawable::~Drawable()

src/osg/Texture.cpp

@@ -191,6 +191,7 @@ void Texture::apply(State& state) const
         if (_subloadMode == OFF)
         {
             glBindTexture( GL_TEXTURE_2D, handle );
+            glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, _min_filter);
         }
         else  if (_image.valid() && _image->data())
         {

src/osgUtil/CullVisitor.cpp

@@ -895,11 +895,18 @@ void CullVisitor::apply(Geode& node)
     Matrix* matrix = getCurrentMatrix();
     for(int i=0;i<node.getNumDrawables();++i)
     {
-
         Drawable* drawable = node.getDrawable(i);
         const BoundingBox &bb =drawable->getBound();
 
+	if( drawable->getCullCallback() )
+	{
+	    if( drawable->getCullCallback()->cull( this, drawable ) == true )
+		continue;
+	}
+	else
+	{
             if (isCulled(bb,mode)) continue;
+	}
 
 
         //SandB change: