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Don't overalign aligned values in gpu_readback::align_byte_size (#17007)

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# Objective

Fix alignment calculations in our rendering code.
Fixes #16992 

The `gpu_readback::align_byte_size` function incorrectly rounds aligned
values to the next alignment.
If we assume the alignment to be 256 (because that's what wgpu says it
its) the function would align 0 to 256, 256 to 512, etc...

## Solution

Forward the `gpu_readback::align_byte_size` to
`RenderDevice::align_copy_bytes_per_row` so we don't implement the same
method twice.
Simplify `RenderDevice::align_copy_bytes_per_row`.

## Testing

Ran the code provided in #16992 to see if the issue has been solved +
added a test to check if `align_copy_bytes_per_row` returns the correct
values.
This commit is contained in:
Brezak 2024-12-30 06:51:37 +01:00 committed by François Mockers
parent a590adca63
commit 4f1bc8e2b8
2 changed files with 32 additions and 7 deletions
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11
crates/bevy_render/src/gpu_readback.rs
View File

@ -27,7 +27,7 @@ use bevy_utils::{default, tracing::warn, HashMap};
use encase::internal::ReadFrom;
use encase::private::Reader;
use encase::ShaderType;
use wgpu::{CommandEncoder, COPY_BYTES_PER_ROW_ALIGNMENT};
use wgpu::CommandEncoder;
/// A plugin that enables reading back gpu buffers and textures to the cpu.
pub struct GpuReadbackPlugin {
@ -349,14 +349,17 @@ fn map_buffers(mut readbacks: ResMut<GpuReadbacks>) {
// Utils
pub(crate) fn align_byte_size(value: u32) -> u32 {
value + (COPY_BYTES_PER_ROW_ALIGNMENT - (value % COPY_BYTES_PER_ROW_ALIGNMENT))
/// Round up a given value to be a multiple of [`wgpu::COPY_BYTES_PER_ROW_ALIGNMENT`].
pub(crate) const fn align_byte_size(value: u32) -> u32 {
RenderDevice::align_copy_bytes_per_row(value as usize) as u32
}
pub(crate) fn get_aligned_size(width: u32, height: u32, pixel_size: u32) -> u32 {
/// Get the size of a image when the size of each row has been rounded up to [`wgpu::COPY_BYTES_PER_ROW_ALIGNMENT`].
pub(crate) const fn get_aligned_size(width: u32, height: u32, pixel_size: u32) -> u32 {
height * align_byte_size(width * pixel_size)
}
/// Get a [`ImageDataLayout`] aligned such that the image can be copied into a buffer.
pub(crate) fn layout_data(width: u32, height: u32, format: TextureFormat) -> ImageDataLayout {
ImageDataLayout {
bytes_per_row: if height > 1 {

28
crates/bevy_render/src/renderer/render_device.rs
View File

@ -231,10 +231,16 @@ impl RenderDevice {
buffer.map_async(map_mode, callback);
}
pub fn align_copy_bytes_per_row(row_bytes: usize) -> usize {
// Rounds up `row_bytes` to be a multiple of [`wgpu::COPY_BYTES_PER_ROW_ALIGNMENT`].
pub const fn align_copy_bytes_per_row(row_bytes: usize) -> usize {
let align = wgpu::COPY_BYTES_PER_ROW_ALIGNMENT as usize;
let padded_bytes_per_row_padding = (align - row_bytes % align) % align;
row_bytes + padded_bytes_per_row_padding
// If row_bytes is aligned calculate a value just under the next aligned value.
// Otherwise calculate a value greater than the next aligned value.
let over_aligned = row_bytes + align - 1;
// Round the number *down* to the nearest aligned value.
(over_aligned / align) * align
}
pub fn get_supported_read_only_binding_type(
@ -248,3 +254,19 @@ impl RenderDevice {
}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn align_copy_bytes_per_row() {
// Test for https://github.com/bevyengine/bevy/issues/16992
let align = wgpu::COPY_BYTES_PER_ROW_ALIGNMENT as usize;
assert_eq!(RenderDevice::align_copy_bytes_per_row(0), 0);
assert_eq!(RenderDevice::align_copy_bytes_per_row(1), align);
assert_eq!(RenderDevice::align_copy_bytes_per_row(align + 1), align * 2);
assert_eq!(RenderDevice::align_copy_bytes_per_row(align), align);
}
}