32-bit OpenColorIO workflow broken when using Metal Compute

[wegmann]

Hi,

I use Affinity Photo for post processing renders from Blender (the 3D software). I export the layers from Blender in 32-bit EXR (linear coloraturas-space) and import them into Affinity Photo. I've followed the steps in your tutorial OpenColorIO baking colour space transforms, in order to display the files (which are in linear colour space when I import them) in Blender's filmic coloraturas space. Everything works perfectly and as expected when Affinity Photo is configured to use OpenGL (Affinity Photo -> Preferences -> Performance -> Display: OpenGL). But when I turn on "Enable Metal Compute Acceleration" and change "Display" from "OpenGL" to "Metal", the colours are displayed wrongly. Moreover, they colours are randomly distorted when I export the project to a PNG. (Only when "Metal" / "Enable Metal Compute Acceleration" are enabled.)

This bug is consistent across my three Macs; a 27" inch iMac (Late 2017) running Mohave, a MacBook Pro running Mohave, and on my brand new 27" iMac (Late 2019) running Catalina.

It is only present when switching "Display" to "Metal" and enabling "Enable Metal Compute Acceleration". When using OpenGL everything seems to work fine. Interestingly, the bug is not present in Affinity Publisher, even when I enable "Metal" + "Enable Metal Compute Acceleration". Thus I suspect, that it is related to the 32-bit preview mode in Affinity Photo.

I have a demo project that demonstrates the bug and will happily provide you with more information if needed.

Best regards,

Nis

Edited March 10, 2020 by wegmann

[Gabe]

Hi @wegmann

Welcome to the forums. 

Can you please attach the demo project so we can have a look?