(open)[HOU-3695]Opacity map artifacts in GPU mode

[gagui]

Hello.

I'm having a problem with a curved plane very close to a cylindrical surface. This plane has mapped opacity.

In CPU mode it renders as expected but in GPU mode some artifacts appear.
If I offset the plane a little bit from the surface it renders ok so I asume there is some problems with the cutoff distance.

[chakarov]

Hello gagui I've reproduced and reported the problem, it seems to be caused by surfaces intersecting each other

[gagui]

But in this case the surfaces are not intersecting in fact they are slightly offset, very close but not intersecting. I could send the scene if it helps.

[chakarov]

I've managed to reproduce it only with intersecting surfaces. A scene will be helpful.

[gagui]

Hello Georgy.

Here you have the scene. If you render it with GPU the problem is evident. If you change to CPU it just renders ok.

[chakarov]

Hi gagui , indeat in your case the surfaces are not intersecting, just really close. Just tested with -0.0003 offset and seems to work fine on my side.

[flat]

Houdini's default units of -0.0003 is 0.3mm, which is a large gap.

As I also reported below, it's the GPU's Secondary rays bias precision issue.
The user needs the same precision as the CPU.

https://forums.chaos.com/forum/v-ray...bias-precision