djeedai / bevy_hanabi / 28010808750

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Build Type

push

github

Committed by web-flow

Commit Message

Fix ribbon sort buffer overruns (#537)

## Problem

When several effects are alive and at least one uses ribbons
(`Attribute::RIBBON_ID`), the app crashes in the render thread on a
frame where spawning a new effect grows the effect metadata buffer:

```
wgpu error: Validation Error
  In a set_bind_group command
    Dynamic binding offset index 1 with offset 128 would overrun the buffer
    bound to BindGroup ... Buffer size is 128 bytes ...
```

## Cause

The ribbon particle sort needs a per-effect fill-dispatch that reads
`GpuEffectMetadata::alive_count` from the global effect metadata buffer
via a dynamic offset. That GPU buffer operation was built in
`batch_effects()` (`EffectSystems::PrepareEffectAssets`), where it
captured the metadata buffer handle and computed its dynamic offset.

But the metadata buffer is only grown to the current frame's effect
count later, in `prepare_effect_metadata()`
(`EffectSystems::PrepareEffectGpuResources`). So on a growth frame,
`batch_effects()` captured last frame's smaller buffer together with an
offset computed for the grown layout. When the cached bind group was
validated at dispatch, the dynamic offset overran the (stale) buffer.

## Fix

Defer building the sort fill-dispatch op to a new
`queue_sort_fill_dispatch_ops()` system that runs **after**
`prepare_effect_metadata()` has (re-)allocated the buffer and **before**
the args buffer is uploaded. This mirrors the existing init
fill-dispatch path (`InitFillDispatchQueue` /
`queue_init_fill_dispatch_ops`):

- `batch_effects()` now only records the intent (metadata table id +
indirect dispatch index) into a new `SortFillDispatchQueue`.
- `queue_sort_fill_dispatch_ops()` captures the now-correctly-sized
buffer and computes in-bounds offsets, then submits.

Also added a `debug_assert` in `GpuBufferOperations::create_bind_groups`
that a dynamic-offset source binding fits its buffer, to surface this
class of mistake as an actionable panic rather than a deep wgpu
vali... (continued)

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