Render settings for camera projection

[thomas_bussey]

I'm trying out a camera projection workflow using 'Camera Map Per Pixel' node. Basically I've rendered an HD image of an interior, projected that image back on to my scene using the above node, and rendered a sequence from an animated camera.

My question is what render settings I should use to render out the sequence. So this a normally rendered image with GI, direct lighting etc. What I've done so far is to plug that 'Camera Map Per Pixel' node in to the diffuse slot of a VrayMtl, set this as override material and turned off all lights, GI, glossy effects, filtering. My sequence comes from a RawDiffuseFilter RE. I've turned off all map filtering

The problem I'm getting is that the resulting image (the projected one) is much grainier/noisier than the source.

There's a setting in the CMPP node for a 'z-buffer' maybe it has something to do with that? I added a z-depth RE of the scene but it didn't seem to do anything. Would I be better off just using scanline or something?

Original image:



Projected image:

[thomas_bussey]

Ok, Scanline seems to work well for the projection - BUT, there's no material override option in scanline. So I'd still like a way to do this in Vray.

[hermit.crab]

Seems like there are not enough AA samples to me. Does it happen with the default render settings? Which V-Ray and host platform version are you using? I just tested this on 3ds Max 2022 with the latest official V-Ray 5, update 2 and it renders identical to the image. Also, can you send the scene (or attach it here) so we can take a look?

[thomas_bussey]

Can you describe what you mean by default settings? I'm assuming you didn't leave lights on? GI, filtering, reflections?

I'll give it a go now.

[thomas_bussey]

This is the result I get from Raw diffuse with default Vray 5 settings. As I say, I think it's texture filtering that seems to kill it, but even with that and all refl/refr off I get the AA issues.

Here's the file, : https://drive.google.com/file/d/13eLnoaCiFSgDw6y0FTOdC3YfuzpA2F43/view?usp=sharing




I've stripped out all the textures except the projection texture.

[hermit.crab]

Thanks for the provided scene. This effect is caused by the overlapping geometry (organic such mostly, because of curved edges), on which the Camera Map Per Pixel is projected. I managed to simplify the scene to a simple plane and two spheres in front (check screencap). This seems to happen in other render engines (tested with Arnold and Scanline), which most likely means that it may be some kind of a limitation of the node. Also, you've forgotten to disable the "Remove Back Face Pixels" in the CMPP, which causes back-facing polygons to be ignored (grey areas on flowers).

I am uncertain of your goal with this methodology, however, hiding all geometry and simply placing a Plane in front of the camera should yield the correct result. If there is something specific you're trying to achieve do tell.