[HOU-4167] Alembic Delayed Motion Blur Artifacts (GPU)

[tobiasroesli]

Hi,

I get some weird artifacts when rendering delayed Alembic's with GPU.

here is the test file:
https://we.tl/t-pWdtX42ZfA

There's also some weird behavior when switching the Physical Camera Exposure to "Disabled" in GPU Mode. If you adjust the "Geometry Samples" for the Motion Blur you get brighter or darker images.
With 2 samples you get the same brightness as the CPU. 4 samples its getting darker. 8 samples is darker then 4 samples and so on. Has the same behavior like the F-Stops but you dont want that with Physical Camera Eyposure "Disabled".

Now the big question is - is it a feature or a bug?

I use Houdini Indie 19.5 Build 805.
V-Ray for Houdini number:22662 hash:7f7f4a2 from 28 Feb 2024 20:26
V-Ray Core 6.20.05 [31923cf8] from 17 Feb 2024

[Gosho.Genchev]

Hey tobiasroesli ,

Does not look like a feature to me For whetever reason, in this specific scenario (GPU rendering, geometry samples >2, Alembic), the Rect light is not illuminating the blurred areas of the geometry.
I've logged this and tagged the thread with the ticket number.

Best regards!

[tobiasroesli]

Hi Gosho.Genchev Thanks for heaving a look into it! I appreciate it very! Cheers