Retrace kills light cache

[BBB3]

Trying to render an interior on V-Ray Next GPU (nightly 4.03.03.28427)
LC enabled, all settings at default, Retrace enabled, gives the horrible result below.
Disabling retrace fixes the splotches but of course, I get lots of light leaks.
These get better with LC Subdivs upped to 2000 and sample size reduced to 0.005
Why is Retrace creating the problem it should be helping to fix?

[Svetlozar Draganov]

Does the same thing happen when rendering on the CPU? LC calculation should be the same after all so I expect to see the same artifacts there.
Would it be possible to send us that scene for investigation?

[BBB3]

I haven't tried rendering on the CPU but will do so. Yes, I'll prep the scene as soon as possible.

[BBB3]

One thing to note is that this only started happening after I added chamfers to all 90-degree edges of my wall object, which added quite a bit of geometry and some very long edges.

[Svetlozar Draganov]

If everything is fine with the geometry, I mean no overlapping faces or something else that affects the quality of the geometry - it should be rendered correctly.
If you got an earlier version of the scene without the chamfers please include it in the file you are about to send.

[BBB3]

Well, that's strange. I was just prepping a scene to send and the problem seems to be gone. I'll post here if it pops its head again.

[BBB3]

Hey. I'm going to be sending the scene after all. It's still happening but only when rendering in perspective view. Not in camera view. See screenshots below.

[BBB3]

I've made a simplified version of the scene. If you open it and render it should create the problem. If you render from VrayCam002, the problem goes away.
I've sent the scene via WeTransfer to support@chaosgroup.com

[Svetlozar Draganov]

Thanks for the scene. I managed to replicate the issue.
I'm not sure whether it related to LC retrace option or to Depth of Field effect from the Camera Settings, each of those resolves the issue.
Is strange it happens only on Perspective camera, all other types of cameras like V-Ray Cam and Physical Cam works fine - this actually could be a confirmation that the issue is more related to DOF rather than LC, Physical Cam and V-Ray Cam has a separate DOF control and the one from the render settings is not taken into account with those cams.

[BBB3]

Yeah. That's pretty strange.

[Svetlozar Draganov]

Reference number of the reported issue is:VGPU-3463
Will keep you posted in terms of any updates.

[Svetlozar Draganov]

Forgot to mention that the same setup works fine on the CPU, so there is something involved with the GPU here.