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Richard Thomson DAZ 3D www.daz3d.com. Direct3d 11 Preview Utah code camp fall 2008. Direct3D 11. CTP in November 2008 DirectX SDK Vista (and beyond) only, not on XP Evolution of Direct3D 10 Compatible with D3D 10 cards. Evolution of Direct3D. Direct3D 9
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Richard Thomson DAZ 3D www.daz3d.com Direct3d 11 PreviewUtah code campfall 2008
Direct3D 11 • CTP in November 2008 DirectX SDK • Vista (and beyond) only, not on XP • Evolution of Direct3D 10 • Compatible with D3D 10 cards
Evolution of Direct3D • Direct3D 9 • Stable, been around for a while • Last version to be deployed on Win XP • Direct3D 10 • First Vista-only version • Big change from D3D 9 • Direct3D 10.1 • Incremental tweak to D3D 10
Direct3D 10/10.1/11 vs. 9 • Enumeration factored out to DXGI • Same DXGI used for 10, 10.1 and 11 • Divide render/texture states into chunks • Chunks of state are immutable objects • “Device state” consists of set of assigned state chunks • Introduces new shader stages beyond vertex and pixel shaders • Tighter API specification => no CAPS
Direct3D 11 Focus • Scalability and performance • Improving the development experience • Extending the reach of the GPU
Direct3D 11 New Features • Tessellation • Compute Shader • Multithreading • Shader Subroutines • Improved Texture Compression • Other Features
Tessellation Input Assembler Direct3D 10 pipeline Plus Three new stages for Tessellation Vertex Shader HullShader Tessellator Domain Shader Stream Output Geometry Shader Rasterizer Pixel Shader Output Merger
Hull Shader HS input: patch control pts One Hull Shader invocation per patch HullShader HS output: Patch control pts after Basis conversion • HS output: • TessFactors (how much to tessellate) • fixed tessellator mode declarations Tessellator DomainShader
Hull Shader Syntax [patchsize(12)] [patchconstantfunc(MyPatchConstantFunc)] MyOutPoint main(uint Id : SV_ControlPointID, InputPatch<MyInPoint, 12> InPts) { MyOutPoint result; … result = TransformControlPoint( InPts[Id] ); return result; }
Tessellator HullShader Note: Tessellator does not see control points • TS input: • TessFactors (how much to tessellate) • fixed tessellator mode declarations Tessellator • TS output: • U V {W} domain points • TS output: • topology • (to primitive assembly) Tessellator operates per patch Domain Shader
Domain Shader HullShader Tessellator • DS input: • control points • TessFactors • DS input: • U V {W} domain points One Domain Shader invocation per point from Tessellator • DS output: • one vertex Domain Shader
Domain Shader Syntax void main( out MyDSOutput result, float2 myInputUV : SV_DomainPoint,MyDSInputDSInputs, OutputPatch<MyOutPoint, 12> ControlPts, MyTessFactorstessFactors ){ … result.Position = EvaluateSurfaceUV( ControlPoints, myInputUV );}
Single Pass Example hull shader tessellator domain shader vertex shader Tessellate! Evaluate surface including displacement Animate/skin Control Points Transform basis, Determine how much to tessellate Tess Factors U V {W} domain points control points in Bezier patch transformed control points patch control points displacement map Sub-D Patch Bezier Patch
Current Authoring Pipeline (Rocket Frog Taken From Loop &Schaefer, "Approximating Catmull-Clark Subdivision Surfaces with Bicubic Patches“) Animation Displacement Map Sub-D Modeling Generate LODs Polygon Mesh
New Authoring Pipeline (Rocket Frog Taken From Loop &Schaefer, "Approximating Catmull-Clark Subdivision Surfaces with Bicubic Patches“) Animation Displacement Map Sub-D Modeling Optimally Tessellated Mesh GPU
Tessellation Summary • Helps us get closer to eliminating “pointy heads” • Scales visual quality across PC hardware configurations • Supports performance increases • Coarse model = compression, faster I/0 to GPU • Rendering tailored to each end user’s hardware • Better cross-platform (Windows + Xbox 360) development experience • Xbox 360 has a subset of D3D11’s tessellation • Parity = ease of cross-platform development • Extra features = innovation for Windows gaming • Render content as the artist created it!
More on Tessellation • GameFest 2008 Slides and Audio • “Direct3D 11 Tessellation” • Kev Gee, Microsoft • “Advanced Topics in GPU Tessellation” • Natasha Tatarchuk, AMD/ATI • “Water-Tight, Textured, Displaced Subdivision Surface Tessellation Using Direct3D 11” • Ignacio Castano, NVIDIA
General Purpose GPU • Data Parallel Computing • GPU performance continues to grow • Many applications scale well to massive parallelism without tricky code changes • Direct3D is the API for talking to GPU • How do we expand Direct3D to GPGPU?
Compute Shader Input Assembler Vertex Shader HullShader Tessellator Domain Shader Stream Output Geometry Shader Rasterizer Data Structure Compute Shader Pixel Shader Output Merger Direct3D 10 pipeline Plus Three new stages for Tessellation Plus Compute Shader
Integrated with Direct3D • Fully supports all Direct3D resources • Targets graphics/media data types • Evolution of DirectX HLSL • Graphics pipeline updated to emit general data structures… • …which can then be manipulated by compute shader… • And then rendered by Direct3D again
Target Applications • Image/Post processing: • Image Reduction • Image Histogram • Image Convolution • Image FFT • A-Buffer/OIT • Ray-tracing, radiosity, etc. • Physics • AI
Computing a Histogram Histogram() { shared int Histograms[16][256]; // array of 16 float3 vPixel = load( sampler, sv_ThreadID ); float fLuminance = dot( vPixel, LUM_VECTOR ); intiBin = fLuminance*255.0f; // compute bin to increment intiHist = sv_ThreadIDInGroup & 16; // use thread index Histograms[iHist][iBin] += 1; // update bin // enable all threads in group to complete SynchronizeThreadGroup;
Computing a Histogram 2 // Write register histograms out to memory: iBin = sv_ThreadIDInGroup.x; if (sv_ThreadID.x < 256) { for (iHist = 0; iHist < 16; iHist++) { int2 destAddr = int2(iHist, iBin); OutputResource.add(destAddr, Histograms[iHist][iBin]); // atomic } } }
Compute Shader Summary • Enables much more general algorithms • Transparent parallel processing model • Full cross-vendor support • Broadest possible installed base • GameFest 2008: • “Direct3D 11 Compute Shader – More Generality for Advanced Techniques” • Chas Boyd, Microsoft
Multithreading • Enables distribution across threads of • Application code • Runtime • Driver • Device: free threaded resource creation • Immediate Context: your single primary device for state & draws • Deferred Contexts: your per-thread devices for state & draws • Display Lists: Recorded sequence of graphics commands • Requires a driver update
Shader Subroutines • Details • Calls must be fast • Binding applies to all primitives in a Draw call • Binding operation must be fast • Need parameter passing mechanism • Need access to textures, samplers, etc. • Advantages • Reduce register usage in Über-shaders • Not worst case of all if statements • Allows specialization of subroutines
Improved Texture Compression • Why? • Existing block palette interpolations too simple • Results often rife with blocking artifacts • No high dynamic range (HDR) support
New Texture Formats • BC6 (aka BC6H) • High dynamic range • 6:1 compression (16 bpc RGB) • Targeting high (not lossless) visual quality • BC7 • LDR with alpha • 3:1 compression for RGB or 4:1 for RGBA • High visual quality
Compression of New Formats • Block compression (unchanged) • Each block independent • Fixed compression ratio • Multiple block types (new) • Tailored to different types of content • Smooth gradients vs. noisy normal maps • Varied alpha vs. constant alpha • Decompression results must be bit-accurate with spec
Comparison Results 1 Orig BC3 Orig BC7 Abs Error
Comparison Results 2 Orig BC3 Orig BC7 Abs Error
Comparison Results 3 HDR Original at given exposure BC6 at given exposure Abs Error
Other Features • Conservative oDepth • 2 GB Resources • Geometry shader instance programming model • Optional double support • Read-only depth or stencil views Addressable Stream Out Draw Indirect Pull-model attribute eval Improved Gather4 Min-LOD texture clamps 16K texture limits Required 8-bit subtexel, submip filtering precision
Thanks Allison Klein Senior Lead Program Manager Direct3DMicrosoft Chas. Boyd Architect Windows Desktop & Gaming Technology Microsoft