fde7968168
OK, so this is tricky. Every frame, `delete_old_work_item_buffers` deletes the mesh preprocessing index buffers (a.k.a. work item buffers) for views that don't have `ViewTarget`s. This was always wrong for shadow map views, as shadow maps only have `ExtractedView` components, not `ViewTarget`s. However, before #16836, the problem was masked, because uploading the mesh preprocessing index buffers for shadow views had already completed by the time `delete_old_work_item_buffers` ran. But PR #16836 moved `delete_old_work_item_buffers` from the `ManageViews` phase to `PrepareResources`, which runs before `write_batched_instance_buffers` uploads the work item buffers to the GPU. This itself isn't wrong, but it exposed the bug, because now it's possible for work item buffers to get deleted before they're uploaded in `write_batched_instance_buffers`. This is actually intermittent! It's possible for the old work item buffers to get deleted, and then *recreated* in `batch_and_prepare_binned_render_phase`, which runs during `PrepareResources` as well, and under that system ordering, there will be no problem other than a little inefficiency arising from recreating the buffers every frame. But, if `delete_old_work_item_buffers` runs *after* `batch_and_prepare_render_phase`, then the work item buffers corresponding to shadow views will get deleted, and then the shadows will disappear. The fact that this is racy is what made it look like #16922 solved the issue. In fact, it didn't: it just perturbed the ordering on the build bots enough that the issue stopped appearing. However, on my system, the shadows still don't appear with #16922. This commit solves the problem by making `delete_old_work_item_buffers` look at `ExtractedView`s, not `ViewTarget`s, preventing work item buffers corresponding to live shadow map views from being deleted. |
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Bevy Render
