VrayDisplacementMod playing up when camera animates upwards and away from displaced surface.

[D3Pixel]

Hi

I am rendering a draft ocean scene over 700 frames where the camera starts low near the wave surface and then rises up to around 400 feet.

This uses a looping PhoenixFDOceanTex as the material and the VRayDisplacementMod on a plane with 1000x1000 divisions and an edge length of 16.

The issue occurs when the camera animates upwards, it looks like the DisplacementMod Edge Length changes dynamically as the camera rises into the sky creating a popping effect where some groups of waves look low quality then switch to a higher quality, this occurs over a single frame then stays like that for another 100 frames then does it again until we reach the full height and the camera stops moving.

If the camera is not moving then this weird LOD popping effect does not happen.
View-Dependent is enabled.

Any ideas how to stop this happening?

[Morbid Angel]

well view-dependent does exactly that but if your subdivision is low, then it might be noticeable pop effect between lods. I would always suggest in this case not to use view-dependent option and instead use grid subdivision, find a value that works for closeup and far back.

[D3Pixel]

I have identified 2 frames (260 + 261) where this quality change is very noticeable so I can at least run small change tests to try identify what causes it. It is like a different smoothing group on one small area of the ocean that suddenly updates.

Edge Length:
Changing Edge Length from 16 to 6 still causes some waves to suddenly change from a lower quality to a higher quality.

VRay Denoiser?
Not that

Motion Blur? (Camera and object)
Hmm, First test with all motion blur disabled and the problem has gone away. Will do more tests now.....
The problem does not come back if I re-enable motion blur on these frames so it might be a random issue. Urgh.
Will render 30 frames and see if it comes back....
Ok, the problem is not visible over 30 frames now, maybe because I am rendering a section from 200 feet high to 300 feet and skipping the very close shots that somehow screw it up later?
I will have to re-run the full render to see if comes back.

[D3Pixel]

well view-dependent does exactly that but if your subdivision is low, then it might be noticeable pop effect between lods. I would always suggest in this case not to use view-dependent option and instead use grid subdivision, find a value that works for closeup and far back.

Well I thought that but then why does it do it on small portions of the waves. On a 1080p screen it does it in the middle-right but all around those waves it does not do it and LOD's should blend not pop so not sure this is it. I have it down to test with view dependant turned off but I imagine my render times will rocket.

[Morbid Angel]

Are you using subdivision or displacement tesselation?

[D3Pixel]

Are you using subdivision or displacement tesselation?

On the DisplacementMod, I am using 3D Mapping with Tangent Displacement.

[Morbid Angel]

In that case its not the same as direct displacement tesselation. Imagine it is doing stepped subidivions, like 2/4/8/16 etc each time you go up 1 level. Its probably one at a certain point you see a bid drop in quality. If you enforce subdivision to world scale it will ensure linear tesselation throughout. Also view dependent is not as useful in that case anyway.

[D3Pixel]

In that case its not the same as direct displacement tesselation. Imagine it is doing stepped subidivions, like 2/4/8/16 etc each time you go up 1 level. Its probably one at a certain point you see a bid drop in quality. If you enforce subdivision to world scale it will ensure linear tesselation throughout. Also view dependent is not as useful in that case anyway.

If this current render still fails then I will try it without view dependant on, cheers. On a side note, there is no way to cache the displacement is there? I wait 2 mins per frame for "compiling geometry" before it even starts rendering.