So whenever I add any material, whether I make it from scratch, using either RPR Uber ot Principled shader, or even on from the RPR library, I get this horrible pure white interference. Maybe it's more common than I think, but it doesnt appear with the same model when rendered with Cycles, and if I don't apply any material and render with ProRender it's perfect. This shows up if there is any light source "activated", whether it's a physical sky, hdri or regular lights. Even if I turn the light source down to zero, the same "noise" appears just as brightly, but in complete blackness around. The actual level of the lighting has no effect on it, and if I actually disable the light or environment light it goes away, and is obviously just a blank black screen. Now if I have the light clamp on,(1.0 as low as it goes), it significantly reduces the brightness of it, but it's still very problematic. It really appears where it should actually be the darkest, like inside open geometry and from the back sides of open objects. I'v checked a lot of things like the normals etc. like under the eve of the house model, in one of the pics I actually have a point light right under it, and it never changes how that noise shows up. It does develop somewhat worse as the render progresses, but it's there from the first few iterations and as far as like, if I "look" up into the roof between the gap where a gutter would be, the whole inside of the roof gets 100% white pixels, when you would think NO light would get there, and that's even with the only light in the scene at 0% in pitch blackness elsewhere. now if I strip the 2 materials off and leave none, and render with just default surfaces it is 100% perfect, aside from the normal level of noise which renders away quickly, everything else looks great, and up inside the roof is nice and dark, because there's no light getting in there. I have tried for days to fix this, and look for answers online, but it is very hard to query for such a specific issue. please look at the pictures and let me know if I can provide anything else to help. Maybe I'm just missing some limitation I'm not aware of. While I'm here also, the reason I'm trying to use blender is because while I prefer Cinema 4D I also have an issue with ProRender in that program, whenever 2 surfaces are touching or close to each other, but only within certain angles, I get these "black" areas, and I've read that it may be related to phong angles but I can't seem to figure that out either. Just for the hell of it I also attached the last 2 pics from C4D renders, all I have done between the two screen grabs is raise the sphere straight up until where the 2 surfaces are meeting went from a positive to a negative angle, and you can see the "black" space that forms where they meet, and it is not in any way a shadow because even a spotlight doesn't affect it. Thanks
FWIW I have figured out that if using rendered view port, ALL of this white distortion in the darkest areas goes AWAY, and it renders just fine, but of coarse all the modifiers don't show, and I even removed all of the modifiers and left just one basic piece of geometry with the RPR shader material on it, and it is overly horrible without it clamped, a bit less with it clamped, and completely perfect in edit mode. I don't get it.
I switched from Global Illumination to Direct illumination in the RPR menu. and the problem goes away, I'm guessing in edit mode it might switch to direct. I've never had to switch OFF GI before, either in Blender or any other program, usually the opposite, I've needed it on. Without GI nothing transparent will look right. I attached 1 more pic, this really stinks.