Blender Version
Broken: maybe since 2.80?
Short description of error
At some point it was possible to force an OpenCL device to be picked up with CYCLES_OPENCL_SPLIT_KERNEL_TEST=1 in the environnement but it's apprently gone. I can see in opencl_util.cpp:861 that a flag exists for that very reason but it seems it was never implemented, could it be possible to set that flag to true with an option/env variable?
| rC Cycles | |||
| D7202 | rC6b063eb75f68 OpenCL: Bring back CYCLES_OPENCL_TEST override | ||
I have to admit, this has annoyed me for the longest time as well, previously it was still possible to test opencl on nvidia using the cycles debug menu, but that has broken somewhere as well during one of @Jeroen Bakker (jbakker) 's refactors somewhere during 2.80.
which makes testing kernel changes more annoying than it should be , can we restore the functionality of the debug menu to either it's former glory or decide we don't care and remove the dead options from it
We no longer have the opencl mega kernel rB949ab753bb2e: Cycles OpenCL: Remove OpenCL MegaKernel
The kernel is splitted by default.
I don't understand the difference that this option would make. (We can't just bring the mega kernel back).
Could you re-enable AMD 7870HD series for Cycles/OpenCL which were deprecated in Blender 2.78?
We are unlikely to bring back support for cards that were deprecated. I don't think the reason behind that decision has changed as the graphics card has not received driver updates for quite a while.
There was a glitch when rendering hair and microdisplacement with OpenCl on that card. Everything else worked.
I brought back the environment variable in D7202 to enable testing on unsupported hardware, leaving this ticket open though since the debug menu should still be either fixed or removed.
OpenCL rendering support was removed in Blender 3.0.
The combination of the limited Cycles kernel implementation, driver bugs, and stalled OpenCL standard
has made maintenance too difficult. Thanks for all your reports, but it's unlikely that there will be further fixes for OpenCL.
For AMD GPUs, there is a new backend based on the HIP platform.
In Blender 3.0, this is supported on Windows with RDNA and RDNA2 generation discrete graphics cards.
It includes Radeon RX 5000 and RX 6000 series GPUs. Driver version Radeon Pro 21.Q4 or newer is required.
https://wiki.blender.org/wiki/Reference/Release_Notes/3.0/Cycles
https://code.blender.org/2021/11/next-level-support-for-amd-gpus/