d3dsw

A software CPU implementation of the Direct3D family of APIs.

API Status

API	Status
Direct3D 11	Feature-complete core
Direct3D 9	Work in progress
Direct3D 7/8	Planned

Feature list

Direct3D 11

Shaders

• Vertex, Pixel, Compute, Geometry, Hull, Domain shaders
• JIT pipeline: DXBC bytecode → C++20 → clang++/MSVC → native .dylib/.dll
• Full SM4.0 / SM5.0 instruction set (arithmetic, integer, bitwise, control flow, atomics, derivatives, bit manipulation)
• All shader stages share the same JIT, codegen, and runtime — frontend is pluggable

Rasterizer

• Tiled rasterizer with 28.4 fixed-point edge functions
• 2×2 quad pixel shader execution (correct derivatives, auto-LOD)
• MSAA: 1×/2×/4×/8×/16×, per-sample coverage/depth/stencil, per-sample shading (SV_SampleIndex), SV_Coverage input/output, LD_MS, ResolveSubresource
• Early-Z with optional Hi-Z acceleration; late-Z when PS uses discard, writes SV_Depth, or uses UAVs
• SV_ViewportArrayIndex, SV_RenderTargetArrayIndex

Geometry / Tessellation

• Geometry Shader, stream output, adjacency topologies, DrawAuto
• Hull Shader + Domain Shader (tri/quad/isoline domains, all partition modes)
• Instanced geometry shaders (DCL_GS_INSTANCE_COUNT)

Textures & Sampling

• 1D / 2D / 3D / Cube textures, mipmap chains, GenerateMips
• Point, bilinear, trilinear filtering; all address modes (wrap, mirror, clamp, border, mirror-once)
• Anisotropic filtering (correct per-pixel footprint, up to 16×)
• SampleLevel, SampleGrad, SampleBias, SampleCmp, SampleCmpLevelZero, Gather, GatherCmp, GatherPO
• BC compressed textures: BC1, BC2, BC3, BC4, BC5, BC7 (BC6H not yet decoded — returns black)
• sRGB read/write

Output Merger

• Depth/stencil: all comparison functions, all stencil ops, Hi-Z
• Blending: all blend factors/ops, dual-source blending, logic ops
• Multi-render-target (up to 8), per-RT write masks, clip/cull distances

Compute

• Thread group shared memory (TGSM), GroupMemoryBarrierWithGroupSync
• Work-stealing thread pool for TGSM-free shaders; barrier-synchronised group pool for shaders with TGSM
• Append/consume buffers, structured buffers, raw buffers, typed UAVs
• Atomic operations (32-bit int/uint, compare-exchange, exchange)

Draw & Dispatch

• Indexed, instanced, indirect draw and dispatch (DrawInstancedIndirect, DispatchIndirect)
• All primitive topologies including adjacency and patch lists

Queries

• D3D11_QUERY_EVENT — CPU/GPU sync point
• D3D11_QUERY_TIMESTAMP / D3D11_QUERY_TIMESTAMP_DISJOINT — timing
• D3D11_QUERY_PIPELINE_STATISTICS — VS/PS/etc invocation counts
• D3D11_QUERY_OCCLUSION / D3D11_QUERY_OCCLUSION_PREDICATE
• D3D11_QUERY_SO_STATISTICS / D3D11_QUERY_SO_OVERFLOW_PREDICATE

Missing / not implemented

The following return E_NOTIMPL or produce no-op results:

• BC6H texture decoding — DXGI_FORMAT_BC6H_UF16 / SF16 texels decode to black. Requires a full BC6H bit-field decoder
• Deferred contexts — CreateDeferredContext, CreateDeferredContext1/2/3. Would require a full command-list record/replay path
• ID3DDeviceContextState (CreateDeviceContextState) — D3D11.1 context snapshot/swap; not implemented
• Tiled resources — UpdateTileMappings, CopyTileMappings, CopyTiles, ResizeTilePool (D3D11.2 sparse resources)
• Fences — CreateFence, OpenSharedFence (D3D11.4 / D3D12-style timeline semaphores)
• Cross-process shared resources — OpenSharedResource, OpenSharedResource1, OpenSharedResourceByName
• Class linkage / shader subroutines — CreateClassLinkage; the INTERFACE_CALL SM5 opcode is not handled
• Performance counters — CreateCounter, CheckCounter, CheckCounterInfo.
• Predicates — CreatePredicate (GPU predicated rendering)
• MSAD4 — the SM5 masked sum-of-absolute-differences instruction
• EVAL_SNAPPED / EVAL_SAMPLE_INDEX / EVAL_CENTROID — SM5 PS interpolation-mode override opcodes
• DXGI factory extras — CreateSwapChainForCoreWindow, CreateSwapChainForComposition, GetWindowAssociation, CreateSoftwareAdapter, stereo/occlusion status events
• DXGI device extras — CreateSurface (DXGI surface sharing), QueryResourceResidency, SetGPUThreadPriority

Direct3D 9 (work in progress)

Shaders

• SM2 and SM3 (vs_2_0 / ps_2_0 / vs_3_0 / ps_3_0): same JIT pipeline as D3D11 — token stream → SM4-shaped IR → C++20 → native code
• Broad SM3 opcode coverage: MOV/ADD/MUL/MAD/DP3/DP4/MIN/MAX, NRM, POW, SINCOS, ABS, LRP, CMP, SLT/SGE, LIT, DST, SGN, CRS, DP2ADD, TEXLD/TEXLDL/TEXLDB/TEXLDP/TEXLDD, TEXKILL, REP/ENDREP, LOOP/ENDLOOP, CALL/CALLNZ/LABEL (subroutine inlining), MOVA, matrix macros (M3x2–M4x4), all source/dest modifiers
• Predicated flow control: SETP, IFC, BREAKC/BREAKP (predicate register p0 mapped to temp)
• SM2 output registers: oPos (RASTOUT[0]) → SV_Position, oD0/oD1 (ATTROUT) → COLOR, oT0–oT7 (TEXCRDOUT) → TEXCOORD — inferred from write scan when no DCL is present
• D3DSPR_MISCTYPE: vPos (→ SV_Position screen-space) and vFace (→ ±1.0 front/back via MOVC)
• Compile-time DEF/DEFI constant folding; sampler/texture binding reconstruction from DCL
• Implicit-LOD SAMPLE dispatches to sw_sample_3d_grad / sw_sample_cube_grad / sw_sample_2d_grad per texture type; screen-space derivatives computed from all UV components across the 2×2 quad

Fixed-Function Pipeline

• VS: WVP transform; normal transform + normalize; full Blinn-Phong lighting (ambient, diffuse, specular) for up to 8 directional/point/spot lights; full material colour source routing (D3DRS_COLORVERTEX, D3DMCS_COLOR1/2/MATERIAL per component); vertex fog (LINEAR/EXP/EXP2); D3DTS_TEXTURE[i] transform (COUNT1–4, PROJECTED)
• PS: all 8 TSS stages chained; color/alpha ops: SELECTARG1/2, MODULATE, MODULATE2X, ADD, ADDSIGNED, SUBTRACT, LERP; args: D3DTA_TEXTURE (white fallback), D3DTA_DIFFUSE, D3DTA_CURRENT, D3DTA_COMPLEMENT, D3DTA_ALPHAREPLICATE
• Custom VS + FF PS and FF VS + custom PS correctly coexist

Fog

• Vertex fog (D3DRS_FOGVERTEXMODE): LINEAR/EXP/EXP2 computed from eye-space Z in the FF VS; custom SM3 VS writes fog factor to oFog (RASTOUT[1])
• Table fog (D3DRS_FOGTABLEMODE): computed per-pixel from eye-space depth (1/perspW) in the rasterizer
• Applied to all active render targets after the PS executes: lerp(fogColor, color, fogFactor)

Device State

• SetRenderState: depth/stencil, blend, cull, fill, scissor, alpha test, separate alpha blend, per-RT write masks, two-sided stencil, slope depth bias, lighting/specular/ambient, fog
• SetTexture / SetSamplerState (stages 0–7)
• SetTransform / MultiplyTransform (512 slots: world, view, projection, texture, bone matrices)
• SetTextureStageState (all 8 stages), SetMaterial, SetLight / LightEnable (up to 8 lights)
• SetClipPlane (6 planes), SetClipStatus
• SetVertexDeclaration, SetFVF, SetStreamSource (16 slots), SetStreamSourceFreq (GPU instancing), SetIndices
• SetVertexShaderConstantF/I/B, SetPixelShaderConstantF/I/B
• CreateStateBlock / BeginStateBlock / EndStateBlock

Instancing

• SetStreamSourceFreq with D3DSTREAMSOURCE_INDEXEDDATA | N (stream 0) and D3DSTREAMSOURCE_INSTANCEDATA | stepRate (per-instance streams)
• Vertex declaration elements on per-instance streams automatically classified as PerInstanceData with the declared step rate

Draw Calls

• DrawPrimitive, DrawIndexedPrimitive, DrawPrimitiveUP, DrawIndexedPrimitiveUP
• All D3D9 primitive topologies including D3DPT_TRIANGLEFAN
• Clear (colour, depth, stencil), Present
• UpdateSurface, UpdateTexture (pixel copy; all resources are system memory)

Resources

• IDirect3DTexture9: mipmap levels, LockRect / UnlockRect, D3DFMT_R8G8B8 24-bpp expand
• IDirect3DCubeTexture9: 6-face flat backing buffer, GetCubeMapSurface, cube-map sampling
• IDirect3DVolumeTexture9 / IDirect3DVolume9: contiguous mip storage, LockBox / UnlockBox, 3D texture sampling
• IDirect3DVertexBuffer9, IDirect3DIndexBuffer9
• IDirect3DSurface9 (render target, depth-stencil, offscreen)
• Private data (SetPrivateData / GetPrivateData / FreePrivateData) on all resources
• Broad D3DFORMAT coverage: BGRA/RGBA families, depth formats, DXT/BC compressed, float HDR, signed bump-map formats, luminance formats, D3DFMT_R3G3B2 (3+3+2-bit packed, expanded on upload)

Factory and Device

• Direct3DCreate9 and Direct3DCreate9Ex — both return a full IDirect3D9Ex implementation
• IDirect3DDevice9Ex: CheckDeviceState (returns S_OK — no lost device), ResetEx, PresentEx, Create*Ex surface variants

Adapter Enumeration

• GetAdapterCount (1 software adapter), GetAdapterIdentifier, GetAdapterModeCount / EnumAdapterModes, GetAdapterModeCountEx / EnumAdapterModesEx, GetDeviceCaps, ValidateDevice, CheckDeviceType/Format

Queries

• CreateQuery: EVENT (always ready), OCCLUSION (returns 0), TIMESTAMP (returns 0)

Missing / deferred

• Clip plane enable in FF VS/PS
• DOTPRODUCT3, BLENDDIFFUSEALPHA, BUMPENVMAP* TSS ops
• ProcessVertices

Screenshots

D3D11

Triangle

Textured Cube

 

Instanced Cubes

Floor — Aliased vs Mipmapped

 

DirectX SDK Samples — Tutorial 10

DirectX SDK Samples — DecalTessellation11

 

D3D9

Scene — Lighting, Texturing, Fog

Tests

750+ tests across three categories:

• Unit tests — device, resources, views, states, formats, shader compilation, draw and compute pipelines, SM3 translator
• Golden tests — pixel-exact comparison against reference images for D3D11 and D3D9 rendering paths
• Perf tests — draw and compute benchmarks

References

• D3D11.3 Functional Spec — rasterization rules, fixed-point precision, LOD calculation, texture filtering
• D3D11 API Reference — API contracts, parameter rules, struct/enum definitions
• Parsing DXBC — DXBC container layout
• d3d11TokenizedProgramFormat.hpp (Windows SDK) — opcode definitions, operand encoding, token layout for SM4/SM5 bytecode
• DirectX9 Graphics Reference