mirror of
https://github.com/bevyengine/bevy
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40c26f80aa
# Objective
Adds a new `Readback` component to request for readback of a
`Handle<Image>` or `Handle<ShaderStorageBuffer>` to the CPU in a future
frame.
## Solution
We track the `Readback` component and allocate a target buffer to write
the gpu resource into and map it back asynchronously, which then fires a
trigger on the entity in the main world. This proccess is asynchronous,
and generally takes a few frames.
## Showcase
```rust
let mut buffer = ShaderStorageBuffer::from(vec![0u32; 16]);
buffer.buffer_description.usage |= BufferUsages::COPY_SRC;
let buffer = buffers.add(buffer);
commands
.spawn(Readback::buffer(buffer.clone()))
.observe(|trigger: Trigger<ReadbackComplete>| {
info!("Buffer data from previous frame {:?}", trigger.event());
});
```
---------
Co-authored-by: Kristoffer Søholm <k.soeholm@gmail.com>
Co-authored-by: IceSentry <IceSentry@users.noreply.github.com>
15 lines
680 B
WebGPU Shading Language
15 lines
680 B
WebGPU Shading Language
// This shader is used for the gpu_readback example
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// The actual work it does is not important for the example
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// This is the data that lives in the gpu only buffer
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@group(0) @binding(0) var<storage, read_write> data: array<u32>;
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@group(0) @binding(1) var texture: texture_storage_2d<r32uint, write>;
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@compute @workgroup_size(1)
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fn main(@builtin(global_invocation_id) global_id: vec3<u32>) {
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// We use the global_id to index the array to make sure we don't
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// access data used in another workgroup
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data[global_id.x] += 1u;
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// Write the same data to the texture
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textureStore(texture, vec2<i32>(i32(global_id.x), 0), vec4<u32>(data[global_id.x], 0, 0, 0));
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}
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