ClippingNode: perform clipping in world space, not in object space.

This fixes clipping for instanced rendering and other situations with
non-identity model matrices.

libs_required/ACG/Scenegraph/ClippingNode.cc

@@ -205,10 +205,10 @@ void ClippingNode::ClippingShaderModifier::modifyVertexIO(ShaderGenerator* _shad
 }
 
 
-void ClippingNode::ClippingShaderModifier::modifyVertexBeginCode(QStringList* _code)
+void ClippingNode::ClippingShaderModifier::modifyVertexEndCode(QStringList* _code)
 {
   for (int i = 0; i < numClipPlanes_; ++i)
-    _code->push_back(QString("gl_ClipDistance[%1] = dot(SG_INPUT_POSOS, g_SlicePlane%1);").arg(i));
+    _code->push_back(QString("gl_ClipDistance[%1] = dot(inverse(g_mWV) * sg_vPosVS, g_SlicePlane%1);").arg(i));
 }
 
 //=============================================================================

libs_required/ACG/Scenegraph/ClippingNode.hh

@@ -174,7 +174,7 @@ private:
 
     void modifyVertexIO(ShaderGenerator* _shader);
 
-    void modifyVertexBeginCode(QStringList* _code);
+    void modifyVertexEndCode(QStringList* _code);
 
   private: