diff --git a/examples/Importers/ImportURDFDemo/UrdfRenderingInterface.h b/examples/Importers/ImportURDFDemo/UrdfRenderingInterface.h
index 8b6a649fd..762f6dc9d 100644
--- a/examples/Importers/ImportURDFDemo/UrdfRenderingInterface.h
+++ b/examples/Importers/ImportURDFDemo/UrdfRenderingInterface.h
@@ -1,53 +1,95 @@
 #ifndef URDF_RENDERING_INTERFACE_H
 #define URDF_RENDERING_INTERFACE_H
 
+///UrdfLink and UrdfModel are the main URDF structures to define a robot
 struct UrdfLink;
 struct UrdfModel;
+///btTransform is a position and 3x3 matrix, as defined in Bullet/src/LinearMath/btTransform
 class btTransform;
 
-
+///UrdfRenderingInterface is a simple rendering interface, mainly for URDF-based robots. 
+///There is an implementation in 
+///bullet3\examples\SharedMemory\plugins\tinyRendererPlugin\TinyRendererVisualShapeConverter.cpp
 struct UrdfRenderingInterface
 {
+	///given a URDF link, convert all visual shapes into internal renderer (loading graphics meshes, textures etc)
+	///use the shapeUid as a unique identified to remove it
 	virtual void convertVisualShapes(int linkIndex, const char* pathPrefix, const btTransform& localInertiaFrame, const UrdfLink* linkPtr, const UrdfModel* model, int shapeUid, int objectIndex) =0;
 	
+	///remove a visual shapes, based on the shape unique id (shapeUid)
 	virtual void removeVisualShape(int shapeUid)=0;
 
+	///update the world transform + scaling of the visual shape, using the shapeUid
 	virtual void syncTransform(int shapeUid, const class btTransform& worldTransform, const class btVector3& localScaling)=0;
 
+	///return the number of visual shapes, for a particular body unique id
 	virtual int getNumVisualShapes(int bodyUniqueId)=0;
 
+	///return the visual shape information, for a particular body unique id and 'shape index'
 	virtual int getVisualShapesData(int bodyUniqueId, int shapeIndex, struct b3VisualShapeData* shapeData)=0;
 	
+	///change the RGBA color for a body unique id and link index
 	virtual void changeRGBAColor(int bodyUniqueId, int linkIndex, const double rgbaColor[4])=0;
 
+	///pick the up-axis, either Y (1) or Z (2)
 	virtual void setUpAxis(int axis)=0;
 	
-    virtual void resetCamera(float camDist, float yaw, float pitch, float camPosX,float camPosY, float camPosZ)=0;
+	///compute the view matrix based on those parameters
+	virtual void resetCamera(float camDist, float yaw, float pitch, float camPosX,float camPosY, float camPosZ)=0;
 	
-    virtual void clearBuffers(struct TGAColor& clearColor)=0;
+	///clear the render buffer with a particular color.
+	virtual void clearBuffers(struct TGAColor& clearColor)=0;
 
+	///remove all visual shapes.
 	virtual void resetAll()=0;
 
-    virtual void getWidthAndHeight(int& width, int& height)=0;
+	///return the frame buffer width and height for the renderer
+	virtual void getWidthAndHeight(int& width, int& height)=0;
+	
+	///set the frame buffer width and height for the renderer
 	virtual void setWidthAndHeight(int width, int height)=0;
+	
+	///set the light direction, in world coordinates
 	virtual void setLightDirection(float x, float y, float z)=0;
-    virtual void setLightColor(float x, float y, float z)=0;
-    virtual void setLightDistance(float dist)=0;
-    virtual void setLightAmbientCoeff(float ambientCoeff)=0;
-    virtual void setLightDiffuseCoeff(float diffuseCoeff)=0;
-    virtual void setLightSpecularCoeff(float specularCoeff)=0;
-    virtual void setShadow(bool hasShadow)=0;
+	
+	///set the ambient light color, in world coordinates
+	virtual void setLightColor(float x, float y, float z)=0;
+	
+	///set the light distance
+	virtual void setLightDistance(float dist)=0;
+	
+	///set the light ambient coefficient
+	virtual void setLightAmbientCoeff(float ambientCoeff)=0;
+	
+	///set the light diffuse coefficient
+	virtual void setLightDiffuseCoeff(float diffuseCoeff)=0;
+	
+	///set the light specular coefficient
+	virtual void setLightSpecularCoeff(float specularCoeff)=0;
+	
+	///enable or disable rendering of shadows
+	virtual void setShadow(bool hasShadow)=0;
+	
+	///some undocumented flags for experimentation (todo: document)
 	virtual void setFlags(int flags)=0;
 
-    virtual void copyCameraImageData(unsigned char* pixelsRGBA, int rgbaBufferSizeInPixels, float* depthBuffer, int depthBufferSizeInPixels,int* segmentationMaskBuffer, int segmentationMaskSizeInPixels,  int startPixelIndex, int* widthPtr, int* heightPtr, int* numPixelsCopied)=0;
+	///provide the image pixels as a part of a stream.
+	virtual void copyCameraImageData(unsigned char* pixelsRGBA, int rgbaBufferSizeInPixels, float* depthBuffer, int depthBufferSizeInPixels,int* segmentationMaskBuffer, int segmentationMaskSizeInPixels,  int startPixelIndex, int* widthPtr, int* heightPtr, int* numPixelsCopied)=0;
     
+  ///render an image, using some arbitraty view and projection matrix
 	virtual void render()=0;
+	
+	///render an image using the provided view and projection matrix
 	virtual void render(const float viewMat[16], const float projMat[16])=0;
     
-    virtual int loadTextureFile(const char* filename)=0;
-    virtual int registerTexture(unsigned char* texels, int width, int height)=0;
+  ///load a texture from file, in png or other popular/supported format
+	virtual int loadTextureFile(const char* filename)=0;
+	
+	///register a texture using an in-memory pixel buffer of a given width and height
+	virtual int registerTexture(unsigned char* texels, int width, int height)=0;
    
-    virtual void activateShapeTexture(int objectUniqueId, int jointIndex, int shapeIndex, int textureUniqueId)=0;
+  ///select a given texture for some visual shape.
+	virtual void activateShapeTexture(int objectUniqueId, int jointIndex, int shapeIndex, int textureUniqueId)=0;
 
 };