Differences between v1 GPU path and v2 Legacy GPU Path

[est77]

While trying to update an app using OCIO v1 to OCIO v2 I found some differences in the GPU path transforms between the 2 versions when applying the transforms to HDR images. CPU transforms match.

I am using OpenColorIO v2.0.0-rc1 with the ACES 1.0.3 config. Same config in both versions.

V1 CPU:

V2 CPU:

V1 GPU:

V2 Legacy GPU:

Thanks!

[est77]

I updated my app to use the final v2.0 release and I can confirm that the clamping is still present in the GPU legacy engine (the one that bakes all transforms into a single 3d LUT).

[chrisbrejon]

Yeah same thing here. We have the exact same behavior in our render view.
Thanks !

[remia]

I think the allocation / allocationvars are lost after optimization (even with optimization == none as they are no-op) so that when extractGpuShaderInfo try to query them in PartitionGPUOps to add the appropriate shaper in the shader nothing is left to see.

I can confirm that when using ociodisplay and trying to apply a ACES2065-1 to ODT - sRGB transform (ACES Config 1.2), the shader generated for gpulegacy doesn't have any log shaper and that's not correct.

[chrisbrejon]

Thanks Remi ! You rock !

[doug-walker]

Hi Remi, thanks. Yes, Patrick and I are aware of the problem. We have a PR in progress.

Though, as an aside, if anyone is implementing their GPU path using "legacy" mode, they are missing out on one of the best features of v2. We will fix this, but we definitely do not recommend this way of working.

[est77]

Thanks for looking into it.