Cycles: IES profiles: light shape & size support

The current IES implementation in Blender appears to discard the information about the shape of IES lights. IES profiles commonly specify the shape (e.g., rectangle, disk) and size (width & height or diameter) of light sources. This for example affects the shape of shadows cast by the given light.

Currently, Blender Cycles reads and discards this information: github.com/blender/cycles/blob/main/src/util/ies.cpp

This behavior is not documented, so it was not immediately obvious to me that some information is lost.

From a practical point of view, I think it's already possible to correctly render an IES profile that specifies a shape. As far as I can tell, using an area light of the specified shape works (i.e., this requires manually reading and converting values).

Nevertheless, I think it would be quite valuable if these specifications were used automatically. If that's something that's unlikely to be added in the near future, I would suggest to at least mention this limitation in the documentation ( docs.blender.org/manual/en/latest/render/shader_nodes/textures/ies.html ).

Best, Delio