CNA-GAP-022: DIRECTX9 ignores mipMap for RenderTarget2D (single level, GetData above level 0 throws) and ignores the MSAA request for RenderTargetCube

CNA snapshot 009d40f5  ·  Known Issues › Functional gaps  ·  source links pinned to 009d40f5

CreateRenderTarget2D discards the mipMap argument and CreateRenderTargetCube discards mipMap and multiSampleCount, so mip chains are never generated and cube targets are never multisampled on DIRECTX9.

Identifier

CNA-GAP-022

Category

Functional gap

Subsystem

Graphics & renderers

Status

Open

Verified against

CNA 009d40f5 (009d40f5dd085c4e674d3479675fac84b12b3e0a)

Evidence basis

Source-verified: read at TARGET, not executed

Tests touching this area

Yes: see Current tests

Affected contract

RenderTarget2D(mipMap = true) and RenderTargetCube(multiSampleCount > 0) on DIRECTX9

Expected behaviour

XNA generates a render target's mip chain when it is unbound (mipMap = true) and multisamples cube targets on HiDef devices that support it.

Actual behaviour at TARGET

DirectX9Renderer.cpp's CreateRenderTarget2D takes bool /*mipMap*/ and creates a single-level target; CreateRenderTargetCube ignores mipMap and multiSampleCount (its header note in D3D9RenderTargets.hpp records both as deliberate named gaps). D3D9RenderTargets.cpp's D3D9RenderTargetRenderer::GetData throws NotSupportedException for level > 0. The public RenderTarget2D and RenderTargetCube constructors still pass the full requested chain (CalculateMipLevels) to their Texture base, so LevelCount reports the requested chain while one level exists; GetData(level > 0) therefore passes the shared range check and is refused only by the renderer. The public MultiSampleCount of a cube target reports the renderer's real value (0), so that part is not misreported.

Source locations

• modules/renderers/directx9/src/DirectX9Renderer.cpp — CreateRenderTarget2D and CreateRenderTargetCube parameters
• modules/renderers/directx9/src/D3D9RenderTargets.cpp — D3D9RenderTargetRenderer::GetData level check

Evidence

Checked by reading the named sources at 009d40f5; nothing was built or executed for this entry. Whether the public LevelCount of such a target reports the requested chain was not traced.

Independent re-verification: Checked by reading the named sources at 009d40f5 and the XNA IL (RenderTargetHelper.CreateSurfaces creates a multisampled surface for cube targets as well); nothing was built or executed for this entry. Checks S, T and U of directx9_smoke_test.cpp exercise the DX9 render-target classes but only with mipMap = false and no cube MSAA, so no test requests a mip chain or reads a lower level.

Focused reproduction

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

Current tests

No DIRECTX9 fixture samples a render target's lower mip levels.

Regression test

A DIRECTX9 fixture that renders into a mipMap target, unbinds and samples level 1.

Blast radius

Bloom, down-sampling and distance-sampled render targets on DIRECTX9.

Workaround

Down-sample manually into smaller targets.