Correct native render-target MSAA allocation

[bkaradzic-microsoft]

Summary

• Select the bgfx render-target/MSAA field instead of ORing its mutually exclusive values. Previously a requested 2x became 4x, and 8x became 16x, mismatching the generated depth attachment.
• Detect render targets with the field mask and do not pass initial pixel data for sampled multisample resources. D3D11 forbids CPU initialization data for that storage.
• Retain zero initialization for ordinary render targets; multisampled sampled storage must be initialized with a framebuffer clear.
• Add native regression coverage for 1x/2x/4x/8x flag selection and matching color/depth framebuffers, plus supported sampled-MSAA allocations.

Independence

Rebased onto master (2a9dc944). No Babylon.js changes, protocol changes, dependency updates, fixture changes, or tolerance changes. This does not include the separate D24 format fallback in #1874.

Validation

Windows x64 / D3D11 / Chakra / RelWithDebInfo, using pinned upstream dependencies and published Babylon.js 9.21.2:

• Native MSAA allocation regression passed.
• Existing external-texture 1x and 4x render controls passed; 4x produced 288 partial-coverage pixels versus zero at 1x.

External-texture review follow-up

Commit b0ea3fc6 also applies exclusive RT/MSAA field selection to the D3D11, D3D12, and Metal external-texture paths through their shared sample-count helper. This addresses the suppressed finding in the earlier Copilot review; the independent BGFX_TEXTURE_MSAA_SAMPLE bit is preserved.

A new bounded native wrapping regression checks exact 1x/2x/4x metadata. Before the fix, its 2x case reports the 4x field; after the fix it passes. All four selected D3D11 tests pass: that regression, native MSAA allocation, and the unchanged external 1x/4x rendering controls. D3D12/Metal runtime coverage is left to their supported CI configurations; the new case respects the existing external/render/multisample skip settings.

[Copilot]

🟡 Changes recommended

Gate unsupported MSAA test cases and apply corrected flag selection to external-texture paths.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Corrects native render-target MSAA flag selection and initialization behavior, with regression coverage.

Changes:

• Selects mutually exclusive MSAA flags correctly.
• Omits CPU initialization data for sampled multisample storage.
• Adds native MSAA tests and registers them in CMake.

File summaries

File	Summary
Plugins/NativeEngine/Source/NativeEngine.cpp	Corrects render-target MSAA flag selection; external-texture paths still need the same fix.
Core/Graphics/Source/Texture.cpp	Adjusts initialization behavior for multisample render targets.
Apps/UnitTests/Source/Tests.NativeEngine.Msaa.cpp	Adds MSAA allocation and framebuffer coverage; unsupported sample levels need to be skipped.
Apps/UnitTests/CMakeLists.txt	Registers the new native test source.

Review details

Suppressed comments (2)

Apps/UnitTests/Source/Tests.NativeEngine.Msaa.cpp:62

• The capability probe does not use the flags that Texture::Create2D actually passes to bgfx: owned textures add BGFX_TEXTURE_BLIT_DST in createFlags above. A backend can therefore report this combination as valid here while rejecting the effective flags used by sampled.Create2D, making the test fail instead of skipping an unsupported allocation. Probe the effective flag set.

                if (!bgfx::isTextureValid(0, false, 1, bgfx::TextureFormat::RGBA8, sampledFlags))

Plugins/NativeEngine/Source/NativeEngine.cpp:1648

• Please apply this field selection to the external-texture path as well. The D3D11/D3D12/Metal GetInfo implementations still OR BGFX_TEXTURE_RT with RenderTargetSamplesToBgfxMsaaFlag(...) (for example, ExternalTexture_D3D11.cpp:204-210), and those flags flow unchanged into Texture::Create2D. Thus wrapped sampled-MSAA resources still carry the same mutually exclusive RT/MSAA combination this change fixes here and can be interpreted as the next sample level. Centralize or reuse the same conditional selection for that shared path.

            // RT and the MSAA levels are values in the same field, not independent bits.
            const auto msaaFlag = RenderTargetSamplesToBgfxMsaaFlag(samples);
            flags |= msaaFlag != BGFX_TEXTURE_NONE ? msaaFlag : BGFX_TEXTURE_RT;

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Lite

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[Copilot]

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Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

[bkaradzic-microsoft]

Addressed the suppressed external-texture MSAA finding from the earlier Copilot review in b0ea3fc as well. D3D11/D3D12/Metal now share field selection that does not OR the single-sample RT value into a multisample level. The new wrapping regression reproduces 2x being labeled as 4x before the fix and verifies exact 1x/2x/4x flags afterward; all four selected D3D11 allocation/rendering controls pass. This complements the effective-BLIT_DST capability-probe fix already published in a1523bb.

[Copilot]

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Copilot couldn't run its full agentic review because it didn't start before the timeout. Make sure your repository has a runner available, or add a copilot-code-review.yml file specifying one with the runs-on attribute. See the docs for more details.

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 5 comments.