I have done some experimenting with the DGS material shader, which is meant to give blurred reflections, as well as meant to act as a physically accurate shader for use with global illumination. I will spare the details, but basically any standard shader, be it lambert or phong or blinn, or what-have-you, is not physically accurate... light energy actually increases once bounced off of these surfaces, which is the opposite of what happens in the real world... mental ray's solution for this is either the dgs material or the dialectric material, to be used in conjunction with the physical light shader, which obey's real world fall-off rules... anyway, it would appear that for some reason direct illumination ceases to function once I apply a DGS shader... in my remarkably simple test scene I start with a blue lambert ball and a white lambert floor, with a point light converted to a mental ray rectangular area light pointed at the ball... with raytrace on and nothing else, the light casts a soft shadow from the ball onto the floor... so far, all is well. next test, I change the ball's lambert into a diffuse blue dgs material... everything else remains the same. What happens now is that the shadow remains, exactly as it was, but the ball COMPLETELY dissapears.... well, let me be more specific. the ball is there, it just doesn't appear in the RGB channel (or, if it does, it has some form of wacky yellow or red or green squares all over the area where teh ball should be, and no color/shading that even remotely resembles a ball. these are obviously errors...). the alpha channel shows pieces of the ball there (sometimes correlating to the wacky colored squares, sometimes not)... ok, very odd... but maybe maya's shaders are messing it up, so now I'll turn on "suppress all maya shaders..." I get the same result. ok, so let me turn my light into a physical light... physical DGS shader, physical light... makes sense, right? so, I apply a physical light shader to the light, adjust the color values accordingly (since, like the energy attributes, the physical light shader's color depends on the inverse-square fall-off law, and is thus rarely ever in the range of 0-1... usually it gets to be quite higher), and hit render. the shadow still looks fine, but the ball, again, gets completely screwed up, now with different colored-square-errors than before... so, I figure I should try turning on global illumination, see what happens... after all, these physically based shaders and lighting (dgs and the physical light) are designed to work with global illumination. So, I turn it on (and add a dgs photon material to my ball, to keep physical accuracy in my photons), and it shows a nice blue color bleed into the shadow... from a partially blue, partially screwed-up-wacky-colored-squared-ball... So now let me turn the floor into a dgs material, completely diffuse white, as it was for the lambert... I also give a dgs photon to the floor, for physical accuracy. now I get a nice GI-only render... blue sphere, blue color bleed... but there is no longer a shadow on the floor, and, in fact, the floor itself seems to have vanished... this is where I am at now, and let me tell you I am remarkably close to flipping out and breaking things... I can only imagine I am doing something wrong, but I have studied and studied and STUDIED the book "Rendering With Mental Ray," and cross-referenced the related material to the mental ray for maya documentation, and everything I am doing should work... What I think the problem may be is that the "lights" parameter under dgs material does not seem to exist... Mental Ray's DGS material has all of the attributes you see in mental ray for maya (diffuse, glossy, specular, shiny, shiny u, shiny v, trans, ior), yet it also has one that is missing. the lights attribute. in mental ray (and, I'd imagine, in XSI), if there is nothing given for that attribute, it is supposed to take into account all lights, but since the paramater simply doesn't exist in mental ray for maya, it seems to me that it is ignoring all lights, except for photon purposes... whats even odder is that the documentation for mental ray for maya says that that parameter is supposed to be there... also, adding evern further oddness, I looked in the physical.mi file, where the DGS/dialectric/physical light/etc materials are stored, and there is a parameter under the DGS material which states ' array light "lights" ' as it should.... maya just doesn't want to display it for some reason. it displays all of the other paramaters... this, essentially, leads me to believe that it is a bug in mental ray for maya... if anyone has any explination on this, it would be GREATLY appreciated. Thank you.