Bump Delta scale is probably Vray's biggest issue

[Muhammed_Hamed]

Hi,

I've got few renders approved by my client, which they requested high resolution for print. Problem is that the look of bump mapping relies on final render resolution in Vray, so if resolution changes bump mapping would look completely different
This is not the first time this was discussed, here is a simple test to show the issue by !funk (note that this issue is present on CPU/GPU, and even VRscans)



Many other renderers don't have this limitation, see Octane and Modo native renderer for example here,





This could be worked around in 2 ways,
-Using normal maps with filtering turned off instead of bump mapping
-Or using bump delta scale for each material, so lets say if your render resolution is doubled, you would use bump delta scale of 2, for every single material in the scene. If you have 50 or 100 materials in your scene, you will need to go in manually and do that for every one of them

It is even more disastrous for the GPU engine, where bump delta scale flag is ignored, so actually there is no way of working around this at all!
I started my project with the GPU engine, and I got my renders approved by client. Now there is no way of making my bump mapping look the same at higher resolution. I need to start from scratch and get my renders approved again, which is a waste of time.. I will probably swap to another renderer that doesn't have this limitation for now, it

This limitation affected my workflow in many different ways, I cannot use viewport IPR, I have to always stick to the final render resolution during look dev, and rely on render regions if I want my bump mapping to always look the same.

This is been reported few times already, and Vlado said they are doing research to improve this. It is been nearly 2 years since !funk's thread about this issue
https://forums.chaosgroup.com/forum/...der-resolution

Why haven't this been solved yet?
Why is that other renderers don't have this limitation, it is only Vray??
There has to be a global multiplier for bump delta scale, it is silly that I would need to change that for every material in the scene. And this needs to work on GPU, currently there is just no workaround.


Best,
Muhammed

[tanya_to]

Hello! It's a known issue, which is already logged under VGPU-3819. I'll bump its priority.

[Muhammed_Hamed]

Yeah, logged in for 2 years so far
And for the CPU engine, using bump delta scale is a terrible workaround.. what if I have like a 100 materials in my scene?
I would need to change bump delta scale for each material one by one, and every time I change my render resolution?
Why other renderers don't have this limitation?
I have 14 Vray licenses and like 30 render nodes, then I end up using another renderer for this. And now I need to start from scratch and get my renders approved again
...

[^Lele^]

You can use the standard max Bump slot meanwhile, which wont' suffer of any of these issues.
Edit: nevermind, it does too.
Edit2: And so do Corona and Arnold.

[Muhammed_Hamed]

Octane, Fstorm and Modo renderer don't have this limitation like what I showed in my screenshots
I knew Arnold had it in the past.. but surprised Corona has this issue as well
Not sure about Cycles or RS will test these tonight. I will do this project in Octane most likely

[^Lele^]

For the changing of delta across all materials and maps, it's a simple script, the working skeleton of which i'm attaching you below.
Change the number to suit your needs, and then run the open script (ctrl+e, in the maxscript editor).
It will also create an undo entry, so you'll be able to revert it if you don't like the results.

for m in (getClassInstances vraycolor2bump) do m.bump_delta_scale *= 1

[Muhammed_Hamed]

Thanks for your help ^Lele^
This would be useful in future,
For this project I used the GPU engine, I didn't know bump delta scale is not supported there and I got my renders approved by the client.
I've tried using normal maps as well, but cannot get the same look. I have wasted a lot of time already and need to catch up before the weekend, so should probably start with Octane already
Also my setup is for GPU rendering, the images are very high Res..

A global multiplier for bump delta scale like what your script does would be handy for the CPU engine, and I hope this would work somehow on GPU in future.

[^Lele^]

Yeah, i can only help with little, here.
The thinking was that moving to CPU may be quicker, and overall easier, than moving to another renderer entirely.
As for the GPU issue, it's an unfortunate regression, meaning it was indeed fixed, and broke again some times later, without us realising it.

[Muhammed_Hamed]

So it is not been like this since forever which is good to hear, (the option is removed from the GPU UI in Houdini and Maya btw, so won't be able to tell if this worked in the past or not..I just assumed it didn't)
Getting bump delta scale to work on GPU is first part of the solution, I will ask if there is a similar script to yours for Maya and Houdini plugins, but I wish there would be a global multiplier for convenience
I created a similar rig in Vray for Modo similar to your script, which works nicely!
Will wait for this to be fixed on GPU, then we take it from there.

[1funk]

While having "bump delta scale" working on GPU may be useful, I think it's important to remember that using it to fix this issue is a workaround. It's more important to fix the root issue, so there is no apparent change in bump mapping / roughness, when we change the render resolution.

[Muhammed_Hamed]

It's more important to fix the root issue, so there is no apparent change in bump mapping / roughness, when we change the render resolution.

+1
If Octane, Fstorm and Modo renderer(that was not updated since 2013) can do that, Vray should be able to do the same

[GidPDX]

Has this been fixed yet? This is by far my #1 complaint. The work hours lost adjusting for it outweigh probably any render time savings for most people doing viz/product work in terms of the issues this "feature" fixes in V-ray.

It's probably the only reason I wouldn't ever recommend V-ray to some people esp. if they're bouncing from low to high res print etc. a lot and don't do a lot of animation work.

[vlado]

It will be better in a next update, yes. In the meantime, you can reduce the bitmap blur for your bump maps to something like 0.02 and it will be more consistent.

Best regards,
Vlado

[1funk]

vlado I posted the original thread (linked in the first post: https://forums.chaosgroup.com/forum/...der-resolution).

I'm using V-Ray 3.x for MODO and as far as I can tell, none of the AA/Filtering options in modo affect GPU textures.