Introduction to the Direct3D 11 Graphics Pipeline Allison Klein Senior Lead Program Manager Direct3D Microsoft

Executive Summary: D3D 11 Direct3D 11 focuses on scalability and performance, a creating a better development experience, and extending the reach of the GPU Direct3D 11 is a strict superset of D3D 10 & 10.1 D3D 11 adds support for new features to D3D 10.1 The fastest way to move to Direct3D 11 is to start developing on Direct3D 10/10.1 today Direct3D 11 will be available on Windows Vista & future Windows operating systems Direct3D 11 will run on down-level hardware You can all go back to sleep now.

Outline Overview Drilldown Summary

Direct3D 10 Cleaner API  Easier coding than Direct3D 9 More efficient DDI  Driver Optimization A more consistent experience across hardware! Tighter specification Elimination of caps

Direct3D 10.1 Improved multisampling Improved fixed-function blending MSAA depth access in shader Expose sample positions Explicit coverage control 4-sample MSAA required Improved fixed-function blending Per-MRT blend mode 16-bit integer blending Arrays of cube maps

Direct3D 10.1 (Cont’d) Improved performance over Direct3D 10 6-10% for common cases 20-30% for applications relying on MSAA such as deferred shading engines Algorithms closer to Direct3D 11 and future APIs

Direct3D Issues/Opportunities Scalability Performance Cross-Platform Content and Techniques General-Purpose Data-Parallel Computing

Outline Overview Drilldown Summary

Outline Overview Drilldown Summary Tessellation Compute Shader Multithreading Dynamic Shader Linkage Improved Texture Compression Quick Glance at Other Features Summary

Current Authoring Pipeline (Rocket Frog Taken From Loop &Schaefer, "Approximating Catmull-Clark Subdivision Surfaces with Bicubic Patches“) Sub-D Modeling Animation Displacement Map Polygon Mesh Generate LODs

Character Authoring (Cont’d) Trends Denser meshes, more detailed characters ~5K triangles -> 30-100K triangles More complex animations Animations on polygon mesh vertices more costly Result Indirection in authoring pipeline more painful Painful I/O issues Solution Use higher-level surface representation longer Animate control cage (~5K vertices) Generate displacement & normal maps

Direct3D 10 pipeline Plus Three new stages for Tessellation Input Assembler Direct3D 10 pipeline Plus Three new stages for Tessellation Vertex Shader Hull Shader Tessellator Domain Shader Stream Output Geometry Shader Rasterizer Pixel Shader Output Merger

Hull Shader (HS) One Hull Shader invocation per patch HS input: patch control pts One Hull Shader invocation per patch Hull Shader HS output: Patch control pts after Basis conversion HS output: TessFactors (how much to tessellate) fixed tessellator mode declarations Tessellator Domain Shader

Fixed-Function Tessellator (TS) Hull Shader 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) Domain Shader Tessellator operates per patch

Domain Shader (DS) Hull Shader Tessellator DS input: control points TessFactors DS input: U V {W} domain points Domain Shader One Domain Shader invocation per point from Tessellator DS output: one vertex

Direct3D 11 Pipeline D3D11 HW Feature D3D11 Only Input Assembler Vertex Shader D3D11 HW Feature D3D11 Only Fundamental primitive is patch (not triangle) Superset of Xbox 360 tessellation Hull Shader Tessellator Domain Shader Stream Output Geometry Shader Rasterizer Pixel Shader Output Merger

Example Surface Processing Pipeline Single-pass process! vertex shader hull shader tessellator domain shader Animate/skin Control Points Transform basis, Determine how much to tessellate Tess Factors Tessellate! Evaluate surface including displacement patch control points transformed control points control points in Bezier patch U V {W} domain points Sub-D Patch Bezier Patch displacement map

New Authoring Pipeline (Rocket Frog Taken From Loop &Schaefer, "Approximating Catmull-Clark Subdivision Surfaces with Bicubic Patches“) Sub-D Modeling Animation Displacement Map 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!

Want to Know More? “Direct3D 11 Tessellation” Tuesday, 4:00-4:55pm (Next) Kev Gee (Microsoft) “Advanced Topics in GPU Tessellation” Wednesday, 10:15-11:10am Natasha Tatarchuk (AMD) “Water-Tight, Textured, Displaced Subdivision Surface Tessellation Using Direct3D 11” Wednesday, 1:30-2:25pm Ignacio Castano (NVIDIA)

Outline Overview Drilldown Summary Tessellation Compute Shader Multithreading Dynamic Shader Linkage Improved Texture Compression Quick Glance at Other Features Summary

GPGPU = Data Parallel Computing 4/6/2017 5:47 AM GPGPU = 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?

Direct3D 11 Pipeline Input Assembler Direct3D 10 pipeline Plus Three new stages for Tessellation Compute Shader Vertex Shader Hull Shader Tessellator Domain Shader Stream Output Geometry Shader Rasterizer Data Structure Compute Shader Pixel Shader Output Merger

Integration 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

Example Scenario Render scene Write out scene image Input Assembler Render scene Write out scene image Use Compute for image post-processing Output final image Vertex Shader Hull Shader Tessellator Domain Shader Stream Output Geometry Shader Rasterizer Data Structure Compute Shader Pixel Shader Output Merger

Target Applications Image/Post processing: A-Buffer/OIT Image Reduction Image Histogram Image Convolution Image FFT A-Buffer/OIT Ray-tracing, radiosity, etc. Physics AI

Compute Shader: Summary Enables much more general algorithms Transparent parallel processing model Full cross-vendor support Broadest possible installed base

Want to Know More? “Direct3D 11 Compute Shader— More Generality for Advanced Techniques” Wednesday, 4:00-4:55pm Chas Boyd (Microsoft)

Outline Overview Drilldown Summary Tessellation Compute Shader Multithreading Dynamic Shader Linkage Improved Texture Compression Quick Glance at Other Features Summary

Multithreading Today Physics Graphics AI GPU

Multithreading Today CPU-Bound Graphics Physics AI GPU

D3D11 Multithreading Usage 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

Direct3D 11 Multithreading Now, the following can be distributed across threads: Application Direct3D 11 Runtime Direct3D 11 Drivers Updated Direct3D 10 and 10.1 Drivers

Direct3D 11 Multithreading Application Direct3D 11 Runtime Existing 10/10.1 Drivers Direct3D 11 Driver Direct3D 10/10.1 HW Direct3D 11 HW

Direct3D 11 Multithreading Application Direct3D 11 Runtime New 10/10.1 Drivers Direct3D 11 Driver Direct3D 10/10.1 HW Direct3D 11 HW

Multithreading: Summary Improves performance Scalable across hardware configurations in two ways: # of CPUs Graphics cards/drivers Better cross-platform (Windows+Xbox 360) development experience

Want to Know More? “Multithreaded Rendering for Games” Wednesday, 1:30-2:25pm Matt Lee (Microsoft)

Outline Overview Drilldown Summary Tessellation Compute Shader Multithreading Dynamic Shader Linkage Improved Texture Compression Quick Glance at Other Features Summary

Shader Issues Today Shaders getting bigger, more complex Shaders need to target wide range of hardware Two approaches today: Write specialized shaders Good: Build optimal shaders as specializations Bad: Generates lots of shaders Write “one shader to rule them all” Combines multiple shaders Good: Reduces shader binding changes Bad: Code is complex Answer: Subroutines

Shader Subroutines Über-shader Dynamic Subroutine foo (…) { if (m == 1) { // do material 1 } else if (m == 2) { // do material 2 } if (l == 1) { // do light model 1 } else if (l == 2) { // do light model 2 Material1(…) { … } Material2(…) { … } Light1(…) { … } Light2(…) { … } foo(…) { (*material)(…); (*light)(…); } Application binds appropriate *material, *light

Shader Subroutines Details Advantages 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

Want to Know More? “High Level Shader Language (HLSL) Update—Introducing Version 5.0” Tuesday, 5:05-6:00pm Michael Oneppo (Microsoft)

Outline Overview Drilldown Summary Tessellation Compute Shader Multithreading Dynamic Shader Linkage Improved Texture Compression Quick Glance at Other Features Summary

Why New Texture Formats? Existing block palette interpolations too simple Results often rife with blocking artifacts No high dynamic range (HDR) support NB: All are issues we heard from developers

Two New BC’s for Direct3D11 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

New BC’s: Compression 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 Also new: decompression results must be bit-accurate with spec

Multiple Block Types Different numbers of color interpolation lines Less variance in one block means: 1 color line Higher-precision endpoints More variance in one block means: 2 (BC6 & 7) or 3 (BC7 only) color lines Lower-precision endpoints and interpolation bits Different numbers of index bits 2 or 3 bits to express position on color line Alpha Some blocks have implied 1.0 alpha Others encode alpha

Partitions When using multiple color lines, each pixel needs to be associated with a color line Individual bits to choose is expensive For a 4x4 block with 2 color lines 162 possible partition patterns 16 to 64 well-chosen partition patterns give a good approximation of the full set BC6H: 32 partitions BC7: 64 partitions, shares first 32 with BC6H

Example Partition Table A 32-partition table for 2 color lines

Comparisons Orig BC3 BC7 Abs Error

Comparisons Orig BC3 BC7 Abs Error

Comparisons HDR Original at given exposure Abs Error BC6 at

Outline Overview Drilldown Summary Tessellation Compute Shader Multithreading Dynamic Shader Linkage Improved Texture Compression Quick Glance at Other Features Summary

A Plethora of Other Features 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 Conservative oDepth 2 GB Resources Geometry shader instance programming model Optional double support Read-only depth or stencil views

Outline Overview Drilldown Summary Tessellation Compute Shader Multithreading Dynamic Shader Linkage Improved Texture Compression Quick Glance at Other Features Summary

Direct3D 11 Direct3D 11 is strict superset of Direct3D 10 & 10.1 Direct3D 11 adds support for features like multithreading, tessellation, compute to Direct3D 10.1 The fastest way to move to Direct3D 11 is to start developing on Direct3D 10/10.1 today Direct3D 11 will be available on Windows Vista and future Windows operating systems Direct3D 11 will run on down-level hardware Multithreading! Direct3D 10.1, 10, and 9 hardware/drivers Full functionality (for example, tessellation) will require Direct3D 11 hardware

When Can I Get It? Preview bits will be in November 2008 SDK Will work on Windows Vista Will run on Direct3D10/10.1 hardware Full documentation, samples, etc.

Questions?

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