Nice tutorial Madmax! Guess placing a blue screen 2D flat (along the dashed line?) might help composite the image! For HDRI works only on reflective surfaces! But how will the rest of the image be lit (say we'd like a Modelled Background as against the HDRI)? So I guess two renders will have to be done! One for normal lighting and the rest of the mats and another with just those objects having highly reflective surfaces with the HDRI applied! I also have a question. Say its a curved surface (a sphere), and we are using wide angle lens? How do we ensure that the white is not reflected onto portions of the object? Second how do we ensure that the spheres intersect right along the line of the camera FOV? The bryce camera FOV reference is only up to a distance and thus this could be used only on small objects which are near the camera. For large objects this wouldn't apply as the object would then have to be shrunk the natural lens distortion would be lost! I think, using the sphere with a matteable color (say RGB Blue or green and the object set to a non reflective contra color, say black, and a second render taken which would result in a matte!