Urgent serious bug on sampling + extraTex + pointWorld

[bigbossfr]

Hi,
We have a serious problem on Vray to have a good aliasing on all images on a feature film.
I searched the bug today and i found it.

Here the bug :


Like you see, we have a bad sampling on a region of the image.
We can see this with the "sample rate" render element :



Where is the bug : the bug is when i create a extraTex render element, and i output the pointWorld with the sampler info.




Why the extra Tex point world affect the sampling on the beauty image (??????).

I give you a scene, you will understand. Activate and desactivate the render element, and see the sample rate.
I hope it will be fixed quickly.

V-Ray for Maya version 2.25.01, revision 20601 from Apr 18 2012, 04:49:55, linux64, Maya 2011.

Thanks.

[instinct]

I am not really using VRay in Maya, but the ExtraTex in Max has a checkbox to "affect sampling" which causes the element to be used in the DMC's adaptive sampling. So if you have very bright Values (which you usually have in world position elements) this would cause oversampling.

Regards,
Thorsten

[bigbossfr]

It is right.
When i disable the "consider for Anti-Aliasing", i have a great image.
But the problem is not the oversampling, it is the "downsampling".
So my question is : if i disable the "consider for Anti-Aliasing", is the extraTex render element will have a great sampling ?

[vlado]

There is no bug so there is nothing to fix; like Thorsten mentioned, the Extra Tex element has an option "Consider for AntiAliasing". This option needs to be OFF for your world position pass (the default is ON).

Best regards,
Vlado

[vlado]

There is no bug so there is nothing to fix; like Thorsten mentioned, the Extra Tex element has an option "Consider for AntiAliasing". This option needs to be OFF for your world position pass (the default is ON).

Best regards,
Vlado

[bigbossfr]

Is the extraTex render element will have a great sampling if i disable the "consider for Anti-Aliasing" ?

[instinct]

All renderelements are derived from the RGB, hence their sampling is as good as the RGB.

[vlado]

Is the extraTex render element will have a great sampling if i disable the "consider for Anti-Aliasing" ?

There is no meaningful way to do antialiasing on a world position pass anyway.

Best regards,
Vlado

[bigbossfr]

So, it is not possible to have an "oversampling" (to have a great sampling on the extra tex render element) without to have a "downsampling" on the RGB ?

With "consider for Anti-Aliasing", good sampling on the extraTex, but bad sampling on the region of the RGB :



"Consider for Anti-Aliasing" disabled, good aliasing on the RGB, but bad on the extraTex :



Edit : ok ok Vlado. Thank you. We will do a render layer for this pass.

[instinct]

The filtering should be turned of altogether on the Point Pass. Filtering in the point pass is actually not blending values, but moving the pixel in space so to say, so you usually do not want that anyways.

[bigbossfr]

Yes, i know all "data pass" must be aliased, like Z depth, Point Pass, etc etc... But in practice, i don't know why, for example, Z depth work better when it is anti aliased. Normally we must to render the Z pass aliased, with a big resolution, and resize after in compositing (it is the best method), but we can not do this in this current production/pipeline. So we prefer to render the Z depth with anti aliasing.
But it is strange that an extraTex can downsample the beauty pass (oversample yes, downsample, i don't understand).
Thank you for your answer.

[vlado]

"Consider for Anti-Aliasing" disabled, good aliasing on the RGB, but bad on the extraTex:

Even so, it will work fine. The position pass will still exactly match the antialiasing of the RGB pass. You don't need the world position to be "perfect" in itself. It could be misleading that it is shown with colors in the frame buffer - but keep in mind that it does not store colors at all.

Edit : ok ok Vlado. Thank you. We will do a render layer for this pass.

You can do that if you like, but it's an extra step that you don't really need.

Best regards,
Vlado