Raise Vulkan/DX12/GL max_color_attachment_bytes_per_sample Limit (#6866)

Author: cwfitzgerald

CHANGELOG.md

@@ -221,10 +221,12 @@ By @wumpf in [#6849](https://github.com/gfx-rs/wgpu/pull/6849).
 #### Vulkan
 
 - Allocate descriptors for acceleration structures. By @Vecvec in [#6861](https://github.com/gfx-rs/wgpu/pull/6861).
+- `max_color_attachment_bytes_per_sample` is now correctly set to 128. By @cwfitzgerald in [#6866](https://github.com/gfx-rs/wgpu/pull/6866)
 
 #### D3D12
 
 - Fix no longer showing software rasterizer adapters. By @wumpf in [#6843](https://github.com/gfx-rs/wgpu/pull/6843).
+- `max_color_attachment_bytes_per_sample` is now correctly set to 128. By @cwfitzgerald in [#6866](https://github.com/gfx-rs/wgpu/pull/6866)
 
 ### Examples
 

wgpu-core/src/validation.rs

@@ -1295,7 +1295,7 @@ pub fn validate_color_attachment_bytes_per_sample(
     attachment_formats: impl Iterator<Item = Option<wgt::TextureFormat>>,
     limit: u32,
 ) -> Result<(), u32> {
-    let mut total_bytes_per_sample = 0;
+    let mut total_bytes_per_sample: u32 = 0;
     for format in attachment_formats {
         let Some(format) = format else {
             continue;
@@ -1304,10 +1304,7 @@ pub fn validate_color_attachment_bytes_per_sample(
         let byte_cost = format.target_pixel_byte_cost().unwrap();
         let alignment = format.target_component_alignment().unwrap();
 
-        let rem = total_bytes_per_sample % alignment;
-        if rem != 0 {
-            total_bytes_per_sample += alignment - rem;
-        }
+        total_bytes_per_sample = total_bytes_per_sample.next_multiple_of(alignment);
         total_bytes_per_sample += byte_cost;
     }
 

wgpu-hal/src/dx12/adapter.rs

@@ -425,9 +425,8 @@ impl super::Adapter {
 
         // See https://learn.microsoft.com/en-us/windows/win32/direct3d12/hardware-feature-levels#feature-level-support
         let max_color_attachments = 8;
-        // TODO: determine this programmatically if possible.
-        // https://github.com/gpuweb/gpuweb/issues/2965#issuecomment-1361315447
-        let max_color_attachment_bytes_per_sample = 64;
+        let max_color_attachment_bytes_per_sample =
+            max_color_attachments * wgt::TextureFormat::MAX_TARGET_PIXEL_BYTE_COST;
 
         Some(crate::ExposedAdapter {
             adapter: super::Adapter {

wgpu-hal/src/gles/adapter.rs

@@ -663,8 +663,9 @@ impl super::Adapter {
                 .min(crate::MAX_COLOR_ATTACHMENTS as i32) as u32
         };
 
-        // TODO: programmatically determine this.
-        let max_color_attachment_bytes_per_sample = 32;
+        // 16 bytes per sample is the maximum size of a color attachment.
+        let max_color_attachment_bytes_per_sample =
+            max_color_attachments * wgt::TextureFormat::MAX_TARGET_PIXEL_BYTE_COST;
 
         let limits = wgt::Limits {
             max_texture_dimension_1d: max_texture_size,

wgpu-hal/src/vulkan/adapter.rs

@@ -1052,8 +1052,13 @@ impl PhysicalDeviceProperties {
 
         // TODO: programmatically determine this, if possible. It's unclear whether we can
         // as of https://github.com/gpuweb/gpuweb/issues/2965#issuecomment-1361315447.
-        // We could increase the limit when we aren't on a tiled GPU.
-        let max_color_attachment_bytes_per_sample = 32;
+        //
+        // In theory some tilers may not support this much. We can't tell however, and
+        // the driver will throw a DEVICE_REMOVED if it goes too high in usage. This is fine.
+        //
+        // 16 bytes per sample is the maximum size for a color attachment.
+        let max_color_attachment_bytes_per_sample =
+            limits.max_color_attachments * wgt::TextureFormat::MAX_TARGET_PIXEL_BYTE_COST;
 
         wgt::Limits {
             max_texture_dimension_1d: limits.max_image_dimension1_d,

wgpu-types/src/lib.rs

@@ -1192,7 +1192,10 @@ pub struct Limits {
     /// The maximum allowed number of color attachments.
     pub max_color_attachments: u32,
     /// The maximum number of bytes necessary to hold one sample (pixel or subpixel) of render
-    /// pipeline output data, across all color attachments.
+    /// pipeline output data, across all color attachments as described by [`TextureFormat::target_pixel_byte_cost`]
+    /// and [`TextureFormat::target_component_alignment`]. Defaults to 32. Higher is "better".
+    ///
+    /// ⚠️ `Rgba8Unorm`/`Rgba8Snorm`/`Bgra8Unorm`/`Bgra8Snorm` are deceptively 8 bytes per sample. ⚠️
     pub max_color_attachment_bytes_per_sample: u32,
     /// Maximum number of bytes used for workgroup memory in a compute entry point. Defaults to
     /// 16384. Higher is "better".
@@ -3775,6 +3778,9 @@ impl TextureFormat {
         }
     }
 
+    /// The largest number that can be returned by [`Self::target_pixel_byte_cost`].
+    pub const MAX_TARGET_PIXEL_BYTE_COST: u32 = 16;
+
     /// The number of bytes occupied per pixel in a color attachment
     /// <https://gpuweb.github.io/gpuweb/#render-target-pixel-byte-cost>
     #[must_use]
@@ -3800,11 +3806,13 @@ impl TextureFormat {
             | Self::R32Uint
             | Self::R32Sint
             | Self::R32Float => Some(4),
+            // Despite being 4 bytes per pixel, these are 8 bytes per pixel in the table
             Self::Rgba8Unorm
             | Self::Rgba8UnormSrgb
             | Self::Rgba8Snorm
             | Self::Bgra8Unorm
             | Self::Bgra8UnormSrgb
+            // ---
             | Self::Rgba16Uint
             | Self::Rgba16Sint
             | Self::Rgba16Unorm
@@ -3817,6 +3825,7 @@ impl TextureFormat {
             | Self::Rgb10a2Unorm
             | Self::Rg11b10Ufloat => Some(8),
             Self::Rgba32Uint | Self::Rgba32Sint | Self::Rgba32Float => Some(16),
+            // ⚠️ If you add formats with larger sizes, make sure you change `MAX_TARGET_PIXEL_BYTE_COST`` ⚠️
             Self::Stencil8
             | Self::Depth16Unorm
             | Self::Depth24Plus