VrayFur + opacity + environment = Bug

[viscorbel]

I've recently been working on a lot of projects with carpets.
My workflow is using vrayfur, it does the job well.
There is one bug that is extremely annoying and inconvenient

When vrayfur has a shader with vrayhairinfotx opacity map to soften the fur and the scene uses an environment map or even environment color, the result is broken.
It took some time to track down what causes it, but I tracked it down to vraybackground.

So here is a render with no opacity for fur

Here the opacity is turned on

here is the vraybackground element.


There is a solid box below the fur, so there is no way environment background should affect the opacity.
At the moment the workaround is to remake the scenes so there is no environment map.

If you change the environment to anything else, the color of the problem changes, but it still stays there (try disabling the map in sample scene)
Here is a sample scene.
opacity_bug.zip

[Miro]

According to my tests disabling Embree for hair should give you a better result. Can you confirm it is the same on your end?

[viscorbel]

Confirmed - turning Embree off for hair does solve the problem.
Thanks!

[viscorbel]

Actually, turning Embree off altogether solves the problem, while turning it off for hair still leaves about 5% of fireflies.

[matanov]

You are reaching the max transparency level and the tips of the hairs return the background color, which is VRaySky thus making them glowing. You can raise the "max transp levels" in Global switches to deal with this.

[viscorbel]

That seems to do it thank you!

Is returning the background color the best choice in this case? It seems to give very unexpected results.

[vlado]

Is returning the background color the best choice in this case?

Probably not. There are a few options and we will probably change that eventually.

Best regards,
Vlado