Subdivision Surface: fix a serious performance hit when mixing CPU & GPU. #104441
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Reference: blender/blender#104441
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Delete Branch "angavrilov/blender:pr-subdiv-gpu-cpu-conflict"
Deleting a branch is permanent. Although the deleted branch may continue to exist for a short time before it actually gets removed, it CANNOT be undone in most cases. Continue?
Subdivision surface efficiency relies on caching pre-computed topology
data for evaluation between frames. However, while
eed45d2a23
introduced a second GPU subdiv evaluator type, it still only kept
one slot for caching this runtime data per mesh.
The result is that if the mesh is also needed on CPU, for instance
due to a modifier on a different object (e.g. shrinkwrap), the two
evaluators are used at the same time and fight over the single slot.
This causes the topology data to be discarded and recomputed twice
per frame.
Since avoiding duplicate evaluation is a complex task, this fix
simply adds a second separate cache slot for the GPU data, so that
the cost is simply running subdivision twice, not recomputing topology
twice.
To help diagnostics, I also add a message to show when GPU evaluation
is actually used to the modifier panel. Two frame counters are used
to suppress flicker in the UI panel.
Differential Revision: https://developer.blender.org/D17117
4b4e8ad190
tobf214a0bdf
Sorry about that, I'm trying to assign multiple reviewers but it's not letting me, something else to be fixed.
@blender-bot build
Build started.
@ -418,0 +435,4 @@
if (runtime_data && runtime_data->used_gpu) {
if (runtime_data->used_cpu) {
uiItemL(layout, "Using both CPU and GPU subdivision!", ICON_ERROR);
Leave out the exclamation mark, we should generally not use them in UI text unless it's something really critical.
Also this is not really an error, at most a warning but even then would still go with ICON_INFO.
It's not something users are able to fix in generally, some setup just require it with our current implementation.
bf214a0bdf
tod8bb0d329c