Unbind existing meshes before binding new (#1299)

Minor improvement to GlslProgram to unbind existing meshes before binding new meshes.

source/MaterialXRenderGlsl/GlslMaterial.cpp

@@ -112,7 +112,7 @@ void GlslMaterial::bindMesh(MeshPtr mesh)
         return;
     }
 
-    if (_boundMesh && mesh->getName() != _boundMesh->getName())
+    if (mesh != _boundMesh)
     {
         _glProgram->unbindGeometry();
     }

source/MaterialXRenderGlsl/GlslProgram.cpp

@@ -335,6 +335,12 @@ void GlslProgram::bindMesh(MeshPtr mesh)
         throw ExceptionRenderError("No mesh to bind");
     }
 
+    if (mesh != _boundMesh)
+    {
+        unbindGeometry();
+    }
+    _boundMesh = mesh;
+
     GlslProgram::InputMap foundList;
     const GlslProgram::InputMap& attributeList = getAttributesList();
 

source/MaterialXRenderGlsl/GlslProgram.h

@@ -261,6 +261,9 @@ class MX_RENDERGLSL_API GlslProgram
     // Attribute vertex array handle
     unsigned int _vertexArray;
 
+    // Currently bound mesh
+    MeshPtr _boundMesh;
+
     // Program texture map
     std::unordered_map<string, unsigned int> _programTextures;