Severe reflection glossiness bug and Bucket width

[Moriah]

This is not the first time this is happening but on my current project I can't find a way to fix this issue.

Motion Blur ON. Simple plane reflecting, Black diffuse, GGX, 0.85 glossy, cutoff 0.0. Animated particles, self ilum shader, nothing else. No lights, nothing. Here's what happens: I usually render stuff with 16 bucket width, and i'm having random black squares on my reflection plane. My first thought was cutoff, since i have no lights, i put both shaders cutoff to 0, didn't solve it. Then i tried changing the bucket width to 32, and it somewhat solved it. At least from what i saw in the VFB. When i saved the image it looked completely different and the buckets are still there. Here's the renders:

Bucket 32


Bucket 16 (notice the particles are being cutted aswell as the reflection)


What i see in the buffer, looks darker for some reason:


Very severe example of this happening (bucket 16):


Any ideas?

[vlado]

It's not a bug; just with such drastic blur, the initial sampling of a bucket may miss any geometry completely.

The possible solutions are to increase the min. subdivs for AA to 2 or 3, or to use the progressive sampler.

Best regards,
Vlado

[Moriah]

Ok will have a go at that. What about the VFB brightness on the reflection vs saved image? Happens with all kinds of formats. It's not a matte plane btw.

Thanks!

[Moriah]

Progressive Sampler - 03m34s: Even though the image was clean at 2min, some random pixels kept appearing and dissapearing around those hard areas to clean up.
Adaptive (same AA settings and noise threshold) - 03m02s: Pretty clean now, bit faster than progressive.

Reflection still looks darker in the VFB.

[Moriah]

Ok, it looked clean on a static frame... It's still showing black buckets on the animation, even with 3 min AA on Adaptive...

[vlado]

Keep going up with the min. subdivs until it's solved... or wait the progressive render out.

As for the brightness in the VFB vs saved image, the VFB applies a sRGB color correction to the result, whereas 3ds Max saves most 8-bit file formats with gamma 2.2 correction. The two corrections are very similar except for very dark colors where gamma 2.2 boost the brightness way too much.

Best regards,
Vlado

[gfa2]

I'm having the same issue. I've tried upping the sampler to 6/50 and it looks exactly the same as 1/24. I've tried both Brute Force and Irraniance Map for primary and it looks the same either way. I've tried Probablistic Lights on and off, turning Use Local Subdivs on and off....nothing is helping clean up the noise in this glossy reflection. The red arrows in the attached images are the dark bucket issue, the blue arrows are the noisy glossy reflection.

[joconnell]

AA won't help your reflections, either put your shade rate up a bit or drop your colour threshold in the image sampler to make vray work to a finer standard.

[Moriah]

I can confirm that up-ing minimum AA or shading rate didn't solve the issue. In the end i had to deliver the job and it was a mix of render and comp tricks so the black squares didn't appear. Only thing i can think of is to make the render WAY lighter so it doesn't "bug" out and dark it in post.

[gfa2]

AA won't help your reflections, either put your shade rate up a bit or drop your colour threshold in the image sampler to make vray work to a finer standard.

Thanks. Vlado mentioned to keep raising the min. subdivs so I tried it. I did also try lowering the color threshold and it didn't change anything.