Vray visible to camera bug

[joelly3d]

When there is an object with “visible to camera” unchecked, sometimes it will corrupt the alpha of an object behind it.

We have a scene we can send you to debug which looks like this.
You can see the radially sweeping artifacts in the alpha channel.

Scene file is here: VisibleToCameraErrors.zip

[cheerioboy]

This looks a lot like what I've posted about before, http://forums.chaosgroup.com/showthr...ging-artifacts

[vlado]

Turn off Embree and it will be fine for the time being. We are looking into what's causing this.

Best regards,
Vlado

[yordan.madzhunkov]

Hi, Joelly3D,
I inestigated the problem with your scene. It's a combination of few things: the geometry that is invisible to camera it still present in the scene and rays have to be tracked through it. In the invisible geoemtry there is a ray trap: two planes that are very close to each other. (acting as duplicated faces) This causes some precision problems and some rays get stuck there(if embree is used to trace rays). The default vray ray tracer manages to jump over the trap, because it uses different computation.

This leads to two possible solutions to render the scene:
1. Do not use embree
2. Remove one of the overlaping planes in the invisible object