Add `MULTISAMPLE_ARRAY` feature flag. #8571

LaylBongers · 2025-11-25T20:39:09Z

Connections
Closes #8565

Description
This adds a new MULTISAMPLE_ARRAY entry to TextureFormatFeatureFlags. When TEXTURE_ADAPTER_SPECIFIC_FORMAT_FEATURES is enabled and the feature is supported, applications can use this to create 2D Array textures and views with multi-sampling enabled.

This adds a new MULTISAMPLE_ARRAY entry to Features. When enabled and the feature is supported, applications can use this to create 2D Array textures and views with multi-sampling enabled

Additionally, this is implemented in the Vulkan backend. Following the Vulkan specificiation, this should be allowed:
https://docs.vulkan.org/refpages/latest/refpages/source/VkImageCreateInfo.html
https://docs.vulkan.org/refpages/latest/refpages/source/VkImageViewCreateInfo.html#VUID-VkImageViewCreateInfo-image-04972

However this is not necessarily supported if VK_KHR_portability_subset is used, which is the case for apple platform. In this case support should be detected from multisampleArrayImage.
https://docs.vulkan.org/refpages/latest/refpages/source/VkPhysicalDevicePortabilitySubsetFeaturesKHR.html
~~This isn't currently done yet, instead apple target, which always uses VK_KHR_portability_subset is for now excluded.~~
Now implemented too!

To-Dos

Feedback from someone more experienced with Vulkan. Am I missing something obvious here? Did I interpret the spec right?
Explicit checking for support in VK_KHR_portability_subset is not yet implemented.
~~Currently MULTISAMPLE_ARRAY is marked true on all formats. In theory all formats that support multisample should also support this. Should this be more conservative?~~ Limited to the same degree as MULTISAMPLE_RESOLVE.
~~Given that this bypasses some validation, are there any previous assumptions this breaks? Any things that now need to be explicitly checked?~~ Other limitations should already be caught by other constraints.
If there's low hanging fruit where it could be supported immediately on other platforms too without a lot of changes, that would be a nice-to-have.

Testing
I am actively testing this branch at https://github.com/celphase/indite. Developers with an OpenXR compatible headset should be able to test multiview there.

Squash or Rebase?
Squash

Checklist

Run cargo fmt.
Run taplo format.
Run cargo clippy --tests. If applicable, add:
- --target wasm32-unknown-unknown
Run cargo xtask test to run tests.
If this contains user-facing changes, add a CHANGELOG.md entry.

`MULTISAMPLE_RESOLVE`.

inner-daemons · 2025-11-26T16:16:10Z

You asked about this in matrix, but you should probably still check the portability subset. With new drivers like KosmicKrisp and also HoneyKrisp, simply filtering for "apple" might not be a good idea. Also, other drivers can technically use these extensions.

LaylBongers · 2025-11-26T16:20:35Z

While true that other drivers could use the portability subset, currently WGPU only requests a portability subset on apple, and does not store this in any way. Every other instance of code specifically for the portability extension uses this check. I could properly implement this check but that seems a bit out of scope if everything else does it this way.

teoxoy

I don't think this should be a format flag as none of the platforms make this conditional on the format. It should be an adapter/device feature.

Vulkan (non portability) and D3D12 support this unconditionally. Metal's MTLTextureType2DMultisampleArray requires iOS/iPadOS 14.0+, macOS 10.14+, tvOS 16.0+, visionOS 1.0+. I haven't checked OpenGL ES.

Somewhat related: #4405 - though this is a different usecase.

feature.

is active.

LaylBongers · 2025-11-27T15:36:02Z

I've changed the feature to be an adapter flag instead.

This way it also was a lot easier to add support for portability platforms. I don't however have a device I can test that on.

teoxoy

The implementation looks good but it should have at least a test making sure texture/view creation works and submitting a render pass with such an attachment works.

If there's low hanging fruit where it could be supported immediately on other platforms too without a lot of changes, that would be a nice-to-have.

Exposing the feature unconditionally on D3D12 should be enough to get it going. Metal would need a bit more work (optional feature and changes to view creation).

LaylBongers · 2025-11-28T23:08:51Z

I've added the DX12 platform, though I don't have a device that runs it so I can't test it.
I've added a multisample variant of the multiview tests, as they're the most likely use case for multisampled arrays anyways and it was the easiest to modify to add this.

LaylBongers · 2025-11-28T23:18:01Z

I'm seeing the tests currently fail under DX12? I'll have to check the test in more detail tomorrow to see what exactly is failing.

LaylBongers · 2025-11-29T14:20:17Z

I had a look at it just now and I'm a bit stumped on why the DX12 backend is failing on the test. I'm tempted to just turn off support in DX12 again for now.

inner-daemons

Overall looks very good. If we could add support for Metal that'd be superb but you aren't obligated to do that.

I'll check out the CI failures & test later

inner-daemons · 2025-11-29T20:52:41Z

wgpu-core/src/device/resource.rs

+            if desc.size.depth_or_array_layers != 1
+                && !self.features.contains(wgt::Features::MULTISAMPLE_ARRAY)
+            {


Looks very good

inner-daemons · 2025-11-29T20:57:36Z

wgpu-hal/src/vulkan/adapter.rs

+    /// Features provided by `VK_KHR_portability_subset`.
+    ///
+    /// Strictly speaking this tells us what features we *don't* have compared to core.
+    portability_subset: Option<vk::PhysicalDevicePortabilitySubsetFeaturesKHR<'static>>,


Does this need to be added to device creation?

Where specifically?

Check for references to other *Features members in this struct.

Ah good catch, added to the list.

inner-daemons · 2025-11-29T21:00:10Z

wgpu-types/src/features.rs

+        /// Enables creating texture arrays that are also multisampled.
+        ///
+        /// Without this feature, you cannot create a texture that has both a `sample_count` higher
+        /// than 1, and a `depth_or_array_layers` higher than 1.
+        ///
+        /// Supported platforms:
+        /// - Vulkan (except VK_KHR_portability_subset if multisampleArrayImage is not available)
+        /// - DX12
+        const MULTISAMPLE_ARRAY = 1 << 56;


Any way we could add support to some Metal platforms in this PR? Especially with Apple Vision Pro this would probably be useful

It would be very useful for apple vision pro, but I don't have any apple products to test this on and the support seems to be non-trivial.

What about the support is non-trivial? Isn't it just checking if the OS version is high enough?

According to @teoxoy it would require a few more changes. I have absolutely zero experience with the Metal API.

@LaylBongers Alright. If you'd rather not than can you file an issue for Metal multisample array textures?

Added at #8593.

LaylBongers added 5 commits November 25, 2025 21:21

Add MULTISAMPLE_ARRAY format feature flag.

5e05a96

Add apple feature gate to MULTISAMPLE_ARRAY, as it may not support it.

2738c96

Limit MULTISAMPLE_ARRAY at least to the same degree as

aa937c8

`MULTISAMPLE_RESOLVE`.

Renumber flags to be more pretty ordered with MULTISAMPLE_ARRAY.

3bb4c09

Add changes to CHANGELOG.md.

af4ba15

LaylBongers marked this pull request as ready for review November 26, 2025 10:37

inner-daemons self-requested a review November 26, 2025 16:24

teoxoy self-assigned this Nov 26, 2025

Merge branch 'trunk' into trunk

cd59b23

teoxoy requested changes Nov 27, 2025

View reviewed changes

LaylBongers added 2 commits November 27, 2025 16:13

Expose multisample array as an adapter feature instead of a format

0170194

feature.

Correct changelog for changes to PR.

446bc9e

LaylBongers changed the title ~~Add MULTISAMPLE_ARRAY format feature flag.~~ Add MULTISAMPLE_ARRAY feature flag. Nov 27, 2025

Add MULTISAMPLE_ARRAY feature detection if VK_KHR_portability_subset

486b3af

is active.

Correct docs for MULTISAMPLE_ARRAY feature.

4a395a1

LaylBongers requested a review from teoxoy November 27, 2025 15:52

teoxoy reviewed Nov 27, 2025

View reviewed changes

LaylBongers added 3 commits November 28, 2025 22:44

Add unconditional support for MULTISAMPLE_ARRAY on DX12.

fd0cf14

Add multiview multisample test.

a34c80c

Merge branch 'trunk' into trunk

c0229ce

LaylBongers requested a review from teoxoy November 28, 2025 23:09

inner-daemons suggested changes Nov 29, 2025

View reviewed changes

Add missing push_next for portability_subset.

7e83a5b

LaylBongers mentioned this pull request Nov 29, 2025

Metal support for MULTISAMPLE_ARRAY. #8593

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Add MULTISAMPLE_ARRAY feature flag. #8571

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Add `MULTISAMPLE_ARRAY` feature flag. #8571

Add `MULTISAMPLE_ARRAY` feature flag. #8571

LaylBongers commented Nov 25, 2025 •

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