CNA-GAP-022: DIRECTX9 ignores the MSAA request for RenderTargetCube

CNA snapshot 3b43bd86  ·  Known Issues › Functional gaps  ·  source links pinned to 3b43bd86

CreateRenderTargetCube discards multiSampleCount, so cube render targets are never multisampled on DIRECTX9; the cube target reports MultiSampleCount 0, so nothing is misreported.

Identifier

CNA-GAP-022

Category

Functional gap

Subsystem

Graphics & renderers

Status

Narrowed (partially fixed; describes only what survives)

Verified against

CNA 3b43bd86 (3b43bd8687ed46523d873f9bec4b32bd8481dcb5)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

Yes: see Current tests

Affected contract

RenderTargetCube(multiSampleCount > 0) on DIRECTX9

Expected behaviour

XNA multisamples cube render targets on HiDef devices that support it.

Actual behaviour at TARGET

DirectX9Renderer.cpp's CreateRenderTargetCube takes int /*multiSampleCount*/ and never passes it on, and D3D9RenderTargets.hpp records that D3D9RenderTargetCubeRenderer “deliberately does NOT support MSAA” (MSAA is 2D only). The public MultiSampleCount of such a cube target reports the renderer's real value (0).

Fixed since first recorded: 7c4a986b1 gave DIRECTX9 render targets real mip chains: a mipMap RenderTarget2D or RenderTargetCube allocates its whole chain, regenerates it on every transition away from the target, and GetData reads any level.

Source locations

• modules/renderers/directx9/src/DirectX9Renderer.cpp — CreateRenderTargetCube: multiSampleCount unused
• modules/renderers/directx9/include/CNA/Internal/Renderers/DirectX9/D3D9RenderTargets.hpp — header note: D3D9RenderTargetCubeRenderer deliberately does not support MSAA; mip chains regenerated on unbind
• modules/renderers/directx9/src/D3D9RenderTargets.cpp — the mip-chain regeneration and GetData for any level (7c4a986b1)

Evidence

Checked by reading the named sources at 3b43bd86; nothing was built or executed for this entry.

Independent re-verification: Checked by reading the named sources at 3b43bd86 and the XNA IL (RenderTargetHelper.CreateSurfaces creates a multisampled surface for cube targets as well); nothing was built or executed for this entry.

Re-verified at c6dec91f: 7c4a986b1 made CreateRenderTarget2D and CreateRenderTargetCube pass mipMap through and regenerate the chain on ResolveForTransitionEXT (pinned by RenderTargetUploadRoundTripTests and the cube GetData contract, which CNA records reading level 1 exactly under Wine/DXVK); the cube's multisample count is still unused. Not executed.

Focused reproduction

No focused reproduction is known. Nothing has been invented here; the evidence above is what exists.

Current tests

No DIRECTX9 fixture requests a multisampled cube render target.

Regression test

A DIRECTX9 fixture that requests a multisampled RenderTargetCube on a device that supports it and checks an anti-aliased edge on a face, or a documented refusal.

Blast radius

Multisampled cube render targets (dynamic environment maps with MSAA) on DIRECTX9; 2D targets are multisampled and cube targets render, without MSAA.

Workaround

Render each face into a multisampled RenderTarget2D and copy it into the cube.