standalone GPU bucket render quality bug

[psanitra]

It seems v-ray standalone cannot access/change GPU bucket render quality setting.It always renders what was set in application when exporting the vrscene.(max i my case)

I`ve tried editing the vray scene(text editor), not working.

I tried the parameters via command line -parameterOverride="whatever" , with like all kid of settings for noise,rays,threshold, sizes, etc, they all are picked up and listed as changed in console,but none of it affects GPU bucket quality.

So it is either bugged? or GPU bucket settings are not written/visible in vrscene(first few lines of text as usual)? standalone does not support GPU bucket fully?

All i`m trying to do is simply lower the quality for preview renders(on standalone GPU farm), lets say noise from 0.01 to 0.05, or max samples from 1000 to 10. Both max/standalone are latest production builds.

any advice? thank you.

[savage309]

It is not bugged, but changing the noise level therhold for bucket for V-Ray GPU due to internal reasons is a bit more complicated. The SettignsRTEngine render quality settings are not used for bucket rendering.
The end V-Ray GPU users don’t have to deal with it by themselves, but if you know what you are doing and why, and you still want to change it manually, it is possible.

Make sure you have this parameter exported in the vrscene:
SettingsRTEngine::enable_bucket_sampler=1;

Than you have to have this plugin with the following settings:
SettingsImageSampler {
type=1;
dmc_minSubdivs=sqrt(SettingsRTEngine::gpu_samples_per_pixel*4);
dmc_maxSubdivs=sqrt(SettingsRTEngine::max_sample_level);
dmc_threshold=SettingsRTEngine::noise_threshold;

Where the things on the right you have to compute and save as integers by yourself.
For example, lets say that you want to have bucket render with V-Ray GPU, that renders like progressive with gpu_samples_per_pixel=16, max_sample_level=1024 and noise_threshold = 0.01. Than you will need the following parameters in the SettingsImageSampler:
SettingsImageSampler {
type=1;
dmc_minSubdivs=8; //this is sqrt(16*4)
dmc_maxSubdivs=32;// this is sqrt(1024);
dmc_threshold=0.01;

Let me know if this makes sense,
Best,
Blago.

[psanitra]

I see.

enable_bucket_sampler=1; is already set correctly when exported from max., so that`s good, Thank you for the rest! Is there a document, or command line argument that will write out the list of available settings for the current version?


Overall, the relation between GPU progressive and bucket is not clear at first sight and it`s twisted it many ways. Take these example:

- Ray per pixel settings in max, they affect noise of GPU bucket render. But changing ray pre pixel with standalone command line with -parameterOverride does not affect it. . On the other hand Dmc sampler settings are not present in max GPU UI. But it`s actually what we have to change in command line to change the quality. Now that`s a twist


And Ray per pixel at 16, for bucket mode, which is default, does not adapt to content of what is being rendered and will force to shoot rays even for empty scene. Empty 4k frame will render 50s with 1080TI, no matter how are your other settings(noise or sample limits). This makes for example particle renders, or passes of smaller objects terribly ineffective. Instead of 5 second frame i have to wait 50s.
Is there something that can be done for optimizing rendering of empty space? Redshift bucket mode clearly does not have any issues with it and blazes trough 4k frame in 2s...,

thank you

[savage309]

The reason it is twisted is backward compatibility with older scenes. We can not fix this before the next major V-Ray version unfortunately, so it will be like that for a while.
It is only twisted if you want to modify the scene file somehow yourself.

You can see how rays per pixel maps to bucket sampler from my example above (it goes with some adjustments into the min_subdiv).
It is true that the bucket sampler can be optimized for rendering scenes that are mostly empty, as it currently oversamples in such situations. It is in the todo to fix it for some of the next versions.

We can make the V-Ray cmd arguments work with bucket too though. Will make a note about this.
For future reference, reported as internal issue VGPU-3770

Best,
Blago.

[psanitra]

Sound good. And i completely understand the math behind it, the safety net of slightly default oversampling etc. Makes life easier for new users, avoids usual issues like missing bucket with low motion blur sampling etc. Just keep the options open for guys that know v-ray inside out too, so we can fine tune based on scene needs.

My expectation is that users will move towards using GPU bucket for final render and use progressive for tweaking. But that`s just my 5cents, i never been a fan of progressive modes Time will tell...