Fix material slot overflow in bindless slab#23554
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kristoff3r wants to merge 1 commit intobevyengine:mainfrom
Open
Fix material slot overflow in bindless slab#23554kristoff3r wants to merge 1 commit intobevyengine:mainfrom
kristoff3r wants to merge 1 commit intobevyengine:mainfrom
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When allocating in MaterialBindlessSlab it can hold up to 32 bits of allocations. However, when used on the GPU the slot is packed into 16 bits and combined with the lightmap slot. To fix we set add some debug asserts to validate that the bit packing succeeds, and limit the slab to 16 bits of allocations.
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JMS55
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Mar 28, 2026
kristoff3r
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Isn't this just going to make the bug louder with the asserts and error? I'm not sure how that fixes the bug. |
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When running the example with this PR I don't hit the asserts. My understanding is that the slab saying it's full will cause a new slab to be created instead, but I could be wrong. |
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Ah, right, that makes sense, I didn't realize the Err branch was in try_allocate. And yeah, I tested the example and it does appear to work. |
IceSentry
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Objective
Fixes #23128
When allocating in MaterialBindlessSlab it can hold up to 32 bits of allocations. However, when used on the GPU the slot is packed into 16 bits and combined with the lightmap slot, and when it overflows both slots end up being wrong.
Solution
Add some debug asserts to validate that the bit packing succeeds, and limit the slab to 16 bits of allocations.
I'm not super well versed in this part of the codebase, so I don't know if this is the best spot to put the check, since the limitation isn't really on the slab itself. And I don't know if this has other ramifications that need to be handled.
Testing
Test using the reproducer from the issue.