Enable partial bindless on Metal and reduce bind group overhead (#18149) by holg · Pull Request #23436 · bevyengine/bevy

holg · 2026-03-20T12:38:22Z

Make BUFFER_BINDING_ARRAY conditional on whether the material uses buffer binding arrays. Fix sampler limit to check array element count instead of binding slot count. Only create binding arrays for resource types the material actually uses, reducing overhead on all platforms.

Objective

Fixes #18149
Metal supports TEXTURE_BINDING_ARRAY but not BUFFER_BINDING_ARRAY.
Bindless was disabled entirely on Metal because bindless_supported() required both unconditionally.

Solution

Conditional feature check: Only require BUFFER_BINDING_ARRAY when the material actually uses buffer binding arrays.
Materials using #[data(...)], textures, and samplers (like StandardMaterial) only need TEXTURE_BINDING_ARRAY. Fix sampler limit check: Use max_binding_array_sampler_elements_per_shader_stage (array element count) instead of max_samplers_per_shader_stage (binding slot count).
Only create needed binding arrays: create_bindless_bind_group_layout_entries now skips resource types the material doesn't use. This stays within Metal's 31 argument buffer slot limit and reduces wasted fallback resources on all platforms.

Testing

Bistro Exterior (698 materials), 5-minute runs:

GPU	Avg FPS (before → after)	Min FPS (before → after)	RAM/VRAM
Apple M2 Max (Metal)	115 → 136 (+18%)	60 → 106 (+77%)	-57 MB RAM
NVIDIA 5060 Ti	118 → 217 (+84%)	60 → 165 (+174%)	Same
Intel i360P	25 → 29 (+15%)	Same	Same
AMD Vega 8 / Ryzen 4800U	25 → 25	Same	-88 MB VRAM
Intel Iris XE	~22 → ~22	Same	No regression

Also tested: 3d_scene, pbr, lighting, transmission, deferred_rendering: all pass with zero errors.
Materials using #[uniform(..., binding_array(...))] correctly fall back to non-bindless on Metal.

…engine#18149) Make BUFFER_BINDING_ARRAY conditional on whether the material uses buffer binding arrays. Fix sampler limit to check array element count instead of binding slot count. Only create binding arrays for resource types the material actually uses, reducing overhead on all platforms.

github-actions · 2026-03-20T12:38:30Z

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Copilot

Pull request overview

This PR enables partial bindless support on Metal by making BUFFER_BINDING_ARRAY conditional, fixes the sampler limit check for bindless binding arrays, and reduces bind group overhead by only creating bindless binding arrays for resource types actually used by a material.

Changes:

Make BUFFER_BINDING_ARRAY a conditional requirement based on whether the material uses buffer binding arrays.
Fix bindless sampler limit validation to use max_binding_array_sampler_elements_per_shader_stage (element count) instead of max_samplers_per_shader_stage (binding slots).
Reduce layout + fallback resource overhead by skipping creation of unused bindless sampler/texture binding arrays.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
`crates/bevy_render/src/render_resource/bindless.rs`	Creates bindless bind group layout entries only for the resource types actually used by the material.
`crates/bevy_render/macros/src/as_bind_group.rs`	Updates bindless feature gating and sampler limit checks; passes used bindless resource types into layout entry creation.
`crates/bevy_pbr/src/material_bind_groups.rs`	Skips creating unused sampler/texture binding resource arrays based on the material’s bindless descriptor.

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Copilot · 2026-03-20T12:46:06Z

+/// `used_resource_types` limits which binding arrays are created,
+/// reducing argument buffer slot usage on constrained platforms.
 pub fn create_bindless_bind_group_layout_entries(
    bindless_index_table_length: u32,
    bindless_slab_resource_limit: u32,
    bindless_index_table_binding_number: BindingNumber,
+    used_resource_types: &[BindlessResourceType],
 ) -> Vec<BindGroupLayoutEntry> {


create_bindless_bind_group_layout_entries is a pub function and this signature change adds a required used_resource_types parameter, which is a breaking change for downstream crates that may call it directly. Consider keeping the old signature as a wrapper (e.g. defaulting to all entries in BINDING_NUMBERS), or making the new parameter optional so existing callers continue to compile while still allowing the optimization for generated code.

-1, we don't enforce API stability in rendering guts

Copilot · 2026-03-20T12:46:07Z

 /// Creates the bind group layout entries common to all shaders that use
 /// bindless bind groups.
 ///
-/// `bindless_resource_count` specifies the total number of bindless resources.
-/// `bindless_slab_resource_limit` specifies the resolved
-/// [`BindlessSlabResourceLimit`] value.
+/// `used_resource_types` limits which binding arrays are created,
+/// reducing argument buffer slot usage on constrained platforms.
 pub fn create_bindless_bind_group_layout_entries(
    bindless_index_table_length: u32,
    bindless_slab_resource_limit: u32,
    bindless_index_table_binding_number: BindingNumber,
+    used_resource_types: &[BindlessResourceType],


The rustdoc for create_bindless_bind_group_layout_entries no longer documents bindless_index_table_length, bindless_slab_resource_limit, or bindless_index_table_binding_number, even though they remain public parameters. Please restore brief parameter docs (or an overall explanation) so external callers can understand how to supply correct values.

-1, the comments were out of date

pcwalton

Looks good, had one nit. This will help macOS/iOS performance a lot, thank you!

pcwalton · 2026-03-21T14:24:29Z

    let mut bindless_resource_types = Vec::new();
    let mut bindless_buffer_descriptors = Vec::new();
+    // Whether this material needs buffer binding arrays (BUFFER_BINDING_ARRAY feature).
+    // False when only #[data(...)], textures, and samplers are used.


I might mention in the comment for future readers that if and when wgpu adds support for buffer binding arrays in Metal, we can remove this.

my PR is under review for adding support for buffer binding arrays in Metal: gfx-rs/wgpu#9081

github-actions · 2026-03-21T15:05:28Z

It looks like your PR has been selected for a highlight in the next release blog post, but you didn't provide a release note.

Please review the instructions for writing release notes, then expand or revise the content in the release notes directory to showcase your changes.

kfc35 · 2026-03-23T18:18:06Z

It looks like your PR has been selected for a highlight in the next release blog post, but you didn't provide a release note.

Please review the instructions for writing release notes, then expand or revise the content in the release notes directory to showcase your changes.

This bot is pointing to the wrong links (this has already been fixed)
Here are the corrected links:
directions: https://github.com/bevyengine/bevy/blob/main/_release-content/release_notes.md

directory: https://github.com/bevyengine/bevy/tree/main/_release-content/release-notes

Once you’ve made one, I’ll do a quick look over and place this into ready for final review 😄

holg · 2026-03-24T07:27:28Z

Added release note in _release-content/release-notes/partial_bindless_metal.md. Also addressed pcwalton's nit about the future Metal buffer binding array support comment (referencing wgpu#9081) in the previous commit.

mate-h

Looks good to me overall and is a good improvement! Just a few small comments

mate-h · 2026-03-24T07:41:36Z

                match #actual_bindless_slot_count {
                    Some(bindless_slot_count) => {
                        let bindless_index_table_range = #bindless_index_table_range;
+                        let used_resource_types: &[#render_path::render_resource::BindlessResourceType] = &[


Code style nit pick: does the type need to be explicitly declared here or can it be inferred? Also if it does need to be declared then shorten it by adding an import for that type.

Fair point, it can be inferred from the context..., will change...

mate-h · 2026-03-24T07:44:39Z

+    ];
+
+    // binding arrays only for types that this material uses
+    // Specifically Metal where each binding array uses the buffer slot (limited to 31)


Specify where this limit comes from ie the metal feature set tables or reference a wgpu constant

mate-h · 2026-03-24T07:49:13Z

+        let entry = match resource_type {
+            BindlessResourceType::SamplerFiltering => sampler(SamplerBindingType::Filtering)
+                .count(bindless_slab_resource_limit)
+                .build(**binding_number, stages),


These .count and .build lines are repeated frequently. Maybe reorganize the code so that first you return Some type from the match and then count and build. For the ones with a continue map to None
And skip none after for counting

…ding array creation to reduce code repetition

kfc35 · 2026-03-24T14:26:12Z

@@ -0,0 +1,23 @@
+---


Hm, this file still ended up in release-content and not _release-content 😅 maybe main needs to be merged into your branch if the directory hasn’t been updated

…lindless

…engine#18149) (bevyengine#23436) Make BUFFER_BINDING_ARRAY conditional on whether the material uses buffer binding arrays. Fix sampler limit to check array element count instead of binding slot count. Only create binding arrays for resource types the material actually uses, reducing overhead on all platforms. ## Objective Fixes bevyengine#18149 Metal supports `TEXTURE_BINDING_ARRAY` but not `BUFFER_BINDING_ARRAY`. Bindless was disabled entirely on Metal because `bindless_supported()` required both unconditionally. ## Solution 1. **Conditional feature check**: Only require `BUFFER_BINDING_ARRAY` when the material actually uses buffer binding arrays. 2. Materials using `#[data(...)]`, textures, and samplers (like `StandardMaterial`) only need `TEXTURE_BINDING_ARRAY`. **Fix sampler limit check**: Use `max_binding_array_sampler_elements_per_shader_stage` (array element count) instead of `max_samplers_per_shader_stage` (binding slot count). 3. **Only create needed binding arrays**: `create_bindless_bind_group_layout_entries` now skips resource types the material doesn't use. This stays within Metal's 31 argument buffer slot limit and reduces wasted fallback resources on all platforms. ## Testing Bistro Exterior (698 materials), 5-minute runs: | GPU | Avg FPS (before → after) | Min FPS (before → after) | RAM/VRAM | |-----|--------------------------|--------------------------|----------| | Apple M2 Max (Metal) | 115 → 136 **(+18%)** | 60 → 106 **(+77%)** | -57 MB RAM | | NVIDIA 5060 Ti | 118 → 217 **(+84%)** | 60 → 165 **(+174%)** | Same | | Intel i360P | 25 → 29 **(+15%)** | Same | Same | | AMD Vega 8 / Ryzen 4800U | 25 → 25 | Same | **-88 MB VRAM** | | Intel Iris XE | ~22 → ~22 | Same | No regression | Also tested: `3d_scene`, `pbr`, `lighting`, `transmission`, `deferred_rendering`: all pass with zero errors. Materials using `#[uniform(..., binding_array(...))]` correctly fall back to non-bindless on Metal.

Copilot AI review requested due to automatic review settings March 20, 2026 12:38

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kfc35 added the A-Rendering Drawing game state to the screen label Mar 20, 2026

github-project-automation Bot added this to Rendering Mar 20, 2026

github-project-automation Bot moved this to Needs SME Triage in Rendering Mar 20, 2026

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pcwalton approved these changes Mar 21, 2026

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alice-i-cecile added the M-Release-Note Work that should be called out in the blog due to impact label Mar 21, 2026

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holg mentioned this pull request Mar 22, 2026

Wgpu 29 #23277

Merged

1 task

Add comment about future Metal buffer binding array support (wgpu#9081)

bbf4c85

Add release notes for partial bindless

752dfe7

mate-h reviewed Mar 24, 2026

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holg added 3 commits March 24, 2026 10:32

fix for markdownlint

6eef873

added clarified comment on metal bindings and refactored bindless bin…

2d535fa

…ding array creation to reduce code repetition

fix cargo fmt issues

4dd13e3

kfc35 reviewed Mar 24, 2026

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kfc35 added S-Ready-For-Final-Review This PR has been approved by the community. It's ready for a maintainer to consider merging it and removed S-Waiting-on-Author The author needs to make changes or address concerns before this can be merged labels Mar 24, 2026

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mate-h approved these changes Mar 24, 2026

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holg added 2 commits March 25, 2026 08:52

Merge remote-tracking branch 'upstream/main' into fix/metal-partial-b…

533b54c

…lindless

moved/renamed release-notes to _release-notes

42237aa

alice-i-cecile added this pull request to the merge queue Mar 28, 2026

Merged via the queue into bevyengine:main with commit 3cf98a6 Mar 28, 2026
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github-project-automation Bot moved this from Needs SME Triage to Done in Rendering Mar 28, 2026

mockersf mentioned this pull request Mar 29, 2026

meshes are rendered black on DX12 #23573

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holg commented Mar 20, 2026

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kfc35 commented Mar 23, 2026 •

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