Chapter 5: DirectXChapter 5: DirectX®®

Chas. BoydChas. Boyd

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OutlineOutline• What drove the language design?What drove the language design?

• Background• What does it look like?What does it look like?

• Syntax definition• How does it work?How does it work?

• API integration• How is it used?How is it used?

• Effects Framework

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BackgroundBackground

• The DirectXThe DirectX®® Process Process• Evolution of DirectXEvolution of DirectX®®

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Industry ProcessIndustry Process• Based on iteration with partnersBased on iteration with partners

• Requirements from software developers• Feasibilities from hardware developers

• Combine to deliver product for Combine to deliver product for programmersprogrammers

• Pipelined to work in parallelPipelined to work in parallel• Relies on Reference ImplementationRelies on Reference Implementation

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Direct3D ReferenceDirect3D Reference• Software model of hardwareSoftware model of hardware

•Analogous to/input to “C” model stage of hardware design

• Acts as “compilable specification:”Acts as “compilable specification:”•Used to communicate new features and

requirements to IHVs• Provided as comparison to ISVsProvided as comparison to ISVs

• to check behavior of drivers while coding• Used to test drivers for conformanceUsed to test drivers for conformance• Color rules by Jim BlinnColor rules by Jim Blinn

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Industry ProcessIndustry Process

HardwareVendors

SoftwareDevelopers

End Users

DirectXTeam

DirectX Components New Hardware

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DirectX EvolutionDirectX Evolution

96 97 98 99 00 01 02 03 04

DX9 Float Pixels DX8.1 More Shaders DX8 Programmability DX7 Hardware T&L DX6 Multi-Texture DX5 DrawPrimDX3 1st Direct3D

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Primitive OpsPrimitive Ops

DirectX Graphics ArchitectureDirectX Graphics Architecture

VertexComponents

PixelPixelShaderShader

Samplers

ImageImageSurfaceSurface

VBVB

PosPos ColorColor TC1TC1 TC2TC2

Output pixels

Tex1Tex1

Tex0Tex0

Tex2Tex2

VertexVertexShaderShader

Vec0Vec0 Vec1Vec1 Vec2Vec2 Vec3Vec3 VectorData

GeometryOps

PixelOps

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……

Vertex ShaderVertex ShaderVec0Vec0 Vec1Vec1 Vec2Vec2 Vec3Vec3 Vec4Vec4 Vec15Vec15

Const0Const0

R3R3

R0R0

R11R11

Const1Const1

Const2Const2

Const3Const3

Const95Const95

HposHpos Color0Color0 Color1Color1TC0TC0 TC1TC1 TC2TC2 TC3TC3

…… …

…

Vertex ALUVertex ALU

R1R1

A0A0

R2R2

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Pixel Shader ArchitecturePixel Shader Architecture

Pixel

c0

t3t2

t0

r1

c1c2c3

c7

c4

... Hpos

d0 d1TC0 TC1 TC2 TC3

r0

Pixel ALUt1

Stage3

Stage0

Stage2

Stage1

TextureStages

temp

color

texture constant

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DirectXDirectX®® 6 Multitexture 6 Multitexture

• Texture registersTexture registers 2-82-8• Temp registersTemp registers 11• Color registersColor registers 22• Constant registersConstant registers 11• Output registersOutput registers 00• Instruction countInstruction count 2-82-8• Supports dependent readsSupports dependent reads

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DirectXDirectX®® 8 Pixel 8 Pixel ShadersShaders• Texture registersTexture registers 4 4• Temp registersTemp registers 2 2• Color registersColor registers 2 2• Constant registersConstant registers 8 8• Output registersOutput registers 0 0• Instruction countInstruction count 8 8

•+texture address ops 4

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DirectXDirectX®® 9 Pixel 9 Pixel ShadersShaders• Texture registersTexture registers 1616• Temp registersTemp registers 1212• Color registersColor registers 2 2• Texture CoordinatesTexture Coordinates 8 8• Output registersOutput registers 4 4• Instruction countInstruction count 6464

•+texture address ops 32•Supports flow controlSupports flow control

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DirectXDirectX®® 9.1 Pixel Shaders 9.1 Pixel Shaders

• Texture registersTexture registers 1616• Temporary registersTemporary registers 1616• Color registersColor registers 0 0• Texture CoordinatesTexture Coordinates 8 8• Constant registersConstant registers 6464• Output RegistersOutput Registers 4 4• Instruction countInstruction count 10241024• Dynamic flow controlDynamic flow control

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DirectXDirectX®® 6 API 6 API• Multitexture:Multitexture:

SetTSS( 0, COLOROP, SELECT );SetTSS( 0, COLOROP, SELECT );SetTSS( 0, COLORARG1, TEXTURE );SetTSS( 0, COLORARG1, TEXTURE );

SetTSS( 1, COLOROP, ADD );SetTSS( 1, COLOROP, ADD );SetTSS( 1, COLORARG1, CURRENT );SetTSS( 1, COLORARG1, CURRENT );SetTSS( 1, COLORARG2, TEXTURE );SetTSS( 1, COLORARG2, TEXTURE );

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Multi-Texture MacrosMulti-Texture Macros

SETINSTR( 0, SELECT, TEXTURE, * );SETINSTR( 0, SELECT, TEXTURE, * );SETINSTR( 1, ADD, CURRENT, TEXTURE );SETINSTR( 1, ADD, CURRENT, TEXTURE );

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DirectXDirectX®® 8 Assembly 8 Assembly

tex t0tex t0 ; base texture; base texturetex t1tex t1 ; environment map; environment map

add r0, t0, t1add r0, t0, t1 ; apply reflection; apply reflection

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DirectXDirectX®® 9 HLL Syntax 9 HLL Syntax

outColor = tex2d( baseTextureCoord, outColor = tex2d( baseTextureCoord, baseTexture )baseTexture )+ texCube( EnvironmentMapCoord, + texCube( EnvironmentMapCoord, Environment );Environment );

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Compulsory FiguresCompulsory Figures

• Specular Bump MappingSpecular Bump Mapping• BRDFsBRDFs• Procedural WoodProcedural Wood

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Per-Pixel SpecularPer-Pixel Specular

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BRDFsBRDFs

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Basic Procedural WoodBasic Procedural Wood

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Wood with NoiseWood with Noise

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2-Hemisphere Model2-Hemisphere Model

Sky ColorSky Color

Ground Color

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Hemisphere LightingHemisphere Lighting

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Hemisphere ResultHemisphere Result

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Why an HLL?Why an HLL?

• Scalability vs hwScalability vs hw• Programming complexityProgramming complexity• Higher Level Language solves Higher Level Language solves

thesethese

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Design GoalsDesign Goals

• High level enough to hide High level enough to hide hardware specific detailshardware specific details

• Simple enough for efficient code Simple enough for efficient code generationgeneration

• Familiar enough to reduce Familiar enough to reduce learning curvelearning curve

• With enough optimizing back-ends With enough optimizing back-ends for portabilityfor portability

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Design BaselineDesign Baseline• ‘‘C’ -like syntaxC’ -like syntax• A standard languageA standard language

• like c++ or C# or HTML• in the VS.net IDE

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Graphics ArchitectureGraphics Architecture

Hardware

Driver

Direct3D

D3DX

Application

Code translation

Semantic mapping

Assembler, compiler,effects, utilities

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PreprocessorPreprocessor

• #define#define• #elif#elif• #else#else• #endif#endif• #error#error

• Function-style #defines not Function-style #defines not supportedsupported

• #if#if• #include#include• #line#line• #undef#undef

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TypesTypes

• Basic type is 32-bit floatBasic type is 32-bit float• Structs and arrays supportedStructs and arrays supported• Typedef to shorthand user defined Typedef to shorthand user defined

typestypes• Component access and swizzlesComponent access and swizzles

float float2 float3 float4 float2x1 float2x2 float2x3 float2x4 float3x1 float3x2 float3x3 float3x4 float4x1 float4x2 float4x3 float4x4

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VariablesVariables

• Local / globalLocal / global• StaticStatic

• Global variables that are not externally visible

• ConstConst• Cannot be modified by the shader program• Can be set external to the program

• Can have initializersCan have initializers• Can have semanticsCan have semantics

• For function parameters

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OperatorsOperators

• Pretty much all of C operatorsPretty much all of C operators• Including ?: and sizeof()

• No new language semanticsNo new language semantics• Despite temptation

• Arithmetic operators are per componentArithmetic operators are per component• Matrix multiply is an intrinsic functionMatrix multiply is an intrinsic function• Logical operators are per componentLogical operators are per component• No bitwise operatorsNo bitwise operators

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Statement SyntaxStatement Syntax

• { { [[statementsstatements] ] }}• [[expressionexpression] ] ;;• return return [[expressionexpression] ] ;;• if ( if ( expression expression ) ) statement statement [[else else

statementstatement]]• for ( for ( [[expression expression | | variable_declarationvariable_declaration] ] ; ;

[[expressionexpression] ] ; ; [[expressionexpression] ] ) ) statementstatement

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Intrinsic functionsIntrinsic functionssqrt value sqrt(value a) Square root exp2 value exp2(value a) Base 2 Exp log2 value log2(value a) Base 2 Log min value min(value a, value b) Maximum max value max(value a, value b) Minimum abs value abs(value a, value b) Absolute value len float len(value a) Vector length det float det(value a) Matrix determinant dot float dot(value a) Dot product mul value mul(value a, value b) Matrix multiplication any float any(value a) Logical OR of all input

components all float all(value a) Logical AND of all input

components

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User FunctionsUser Functions

• Standard C-like functionsStandard C-like functions• Output type and input parametersOutput type and input parameters• Parameters can be passed by copy Parameters can be passed by copy

in/copy out mechanismin/copy out mechanism• in/out declaration

• Inlined internally -no recursionInlined internally -no recursion

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Functions (cont.)Functions (cont.)

• Can be static (not externally Can be static (not externally accessible)accessible)

• Non-static functions parameters Non-static functions parameters must have Direct3D declarator must have Direct3D declarator semanticssemantics

• Parameters can be marked constParameters can be marked const• Parameters can have default Parameters can have default

initializersinitializers

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Differences from CDifferences from C

• No pointersNo pointers• No recursionNo recursion

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HLSL SummaryHLSL Summary• Ease of UseEase of Use

• Enable software developers• Consistency of ImplementationConsistency of Implementation

• Enable multiple vendors• Management of EvolutionManagement of Evolution

• Enable multiple generations• Result:Result:

• Fundamental architecture of DXG software stack and higher level language

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Application IntegrationApplication Integration

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Geometry MappingGeometry Mapping

• DirectXDirectX®® 8 Vertex Shaders 8 Vertex Shaders assume a data layoutassume a data layout• Decl & shader code are tied together• Forces shader author to communicate

with geometry provider• Standard register conventions can

help some• Complicates combining shadersComplicates combining shaders

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SemanticsSemantics

• DirectXDirectX®® 9 decouples decl from VS 9 decouples decl from VS• Both decl and VS refer to Both decl and VS refer to semanticssemantics

rather than register namesrather than register names•Direct3D runtime connects appropriate

vertex stream data to Vertex Shader registers

• Key feature of DirectX9 low-level APIKey feature of DirectX9 low-level API•driven by HLSL and shader requirements

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DX8 Vertex DX8 Vertex DeclarationDeclaration

v0v0 skipskip v1v1

Strm0Strm0 Strm1Strm1

Declaration

Vertex layout

vs 1.1vs 1.1mov r0, v0mov r0, v0……

Shader program

Shader handleShader handle

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pospos normnorm diffdiff

Strm0Strm0 Strm1Strm1

pospos normnorm diffdiff

Strm0Strm0

Declaration

Vertex layout

vs 1.1vs 1.1

dcl_position v0dcl_position v0

dcl_diffuse v1dcl_diffuse v1

mov r0, v0mov r0, v0

……

Shader program(Shader handle)

New Vertex New Vertex DeclarationDeclaration

vs 1.1vs 1.1

dcl_position v0dcl_position v0

dcl_diffuse v1dcl_diffuse v1

mov r0, v0mov r0, v0

……

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Vertex DeclarationVertex Declarationstruct D3DVERTEXELEMENT9struct D3DVERTEXELEMENT9{ {

Stream; Stream; // id from setstream()// id from setstream()Offset; Offset; // offset# verts into str// offset# verts into str Type; Type; // float vs byte, etc.// float vs byte, etc. Method; Method; // tessellator op// tessellator opUsage; Usage; // default semantic(pos, etc)// default semantic(pos, etc) UsageIndex UsageIndex // e.g. texcoord[#]// e.g. texcoord[#]

} }

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VS Input SemanticsVS Input Semantics

• position[n]position[n]• blendweight[n]blendweight[n]• blendindices[n]blendindices[n]• normal[n]normal[n]• psize[n]psize[n]• diffuse[n]diffuse[n]• specular[n]specular[n]• texcoord[n]texcoord[n]• tangent[n]tangent[n]• binormal[n]binormal[n]

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VS output / PS input VS output / PS input semanticssemantics• positionposition• psizepsize• fogfog• color[n]color[n]• texcoord[n]texcoord[n]

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  Uses for SemanticsUses for Semantics

• A data binding protocol:A data binding protocol:• Between vertex data and shaders• Between pixel and vertex shaders• Between pixel shaders and hardware • Between shader fragments

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Integrating with Integrating with ApplicationsApplications• Extract dissassembly and use Extract dissassembly and use

as .asm shader code ala DX8as .asm shader code ala DX8• Use compiled shader objectUse compiled shader object

• Enables constant table access• Via ID3DXConstantTable Interface

• Use in an effect objectUse in an effect object• Manage constants, fallbacks, etc.• Via ID3DXEffect Interface

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Language API: Language API: StandaloneStandalone• Compiler returns a VS or PS and a symbol tableCompiler returns a VS or PS and a symbol table

• Maps extern constants to registers• Any expression of constants (i.e. per primitive Any expression of constants (i.e. per primitive

expressions) still performed per vertexexpressions) still performed per vertex• Symbol table is a set of constantsSymbol table is a set of constants

• ID3DXConstantTable interface

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ID3DXConstantTableID3DXConstantTable

• Exposes constant parameter metadataExposes constant parameter metadata• For convenient specification of shader input data

• SetMatrix( “curv”, matrix );SetMatrix( “curv”, matrix );• String or handle• D3DXHandle *hHandle

• SetVector()SetVector()• SetValue()SetValue()

• Use effect parametersUse effect parameters• Per primitive expressions of parameters Per primitive expressions of parameters

computed outside the vertex shadercomputed outside the vertex shader

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Shader ManagementShader Management

• Due to varying effects desired:Due to varying effects desired:•Diffuse, ambient, or specular terms•Skinning on or off, number of lights

• Due to different hardware generationsDue to different hardware generations•DirectX® 8, 9, 9.1

• Apps must manage a combinatoric Apps must manage a combinatoric number of shadersnumber of shaders

• FF pipeline does not have these issuesFF pipeline does not have these issues

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Solution: “Effects”Solution: “Effects”

• D3DX Effect FrameworkD3DX Effect Framework• Routines to load and select shadersRoutines to load and select shaders• Originally developed to manage Originally developed to manage

multitexture shaders in DirectX 6multitexture shaders in DirectX 6• Now fully integrated with the HLSLNow fully integrated with the HLSL

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Effect FrameworkEffect Framework• Encapsulation of device stateEncapsulation of device state• Enables scalable rendering techniquesEnables scalable rendering techniques• Allows controlled fallbackAllows controlled fallback• Can’t just switch to multi-passCan’t just switch to multi-pass

• Older hardware can’t do more passes since fill rate is less

• Helps rapid prototypingHelps rapid prototyping• Runtime interpretation of text-based

effect definition

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Effect Framework Effect Framework GoalsGoals• Standard way of representing shading Standard way of representing shading

algorithmsalgorithms• Ease of authoringEase of authoring• Enable some abstraction between author Enable some abstraction between author

of effect and user of the effectof effect and user of the effect• Facilitates sharing of effects• Enables effect – geometry optimizations to be

done at author-time, install-time, load-time or runtime

• Cross PlatformCross Platform• Efficient for runtime useEfficient for runtime use

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Effect ModelEffect ModelEffect Water

Technique DX8

Technique DX9

Technique DX7

pass0

pass1

pass0

pass0

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Effect FrameworkEffect FrameworkFallback TechniquesFallback Techniques

• Techniques are grouped by their Techniques are grouped by their quality or “LOD”quality or “LOD”

• Techniques can be chosen based on Techniques can be chosen based on what hardware creates successfullywhat hardware creates successfully

• Can test performance in back Can test performance in back bufferbuffer

• User responsible for drawing User responsible for drawing geometrygeometry

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Parameterized EffectsParameterized Effects• Effects can have parameters Effects can have parameters

of various typesof various types• Parameters augment static Parameters augment static

state description in the .fx filesstate description in the .fx files• How (and which) parameters get How (and which) parameters get

used defined by the effectused defined by the effect

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Parameterized EffectsParameterized Effects

• Shared parameters (aka Globals)Shared parameters (aka Globals)• Shared across multiple effects• Tagged in effect file as shared• User selects the list of effects whose shared

parameters are linked at runtime• Setting once updates all linked effects

• Naming convention for artist tweakableNaming convention for artist tweakable• Enables hooking UI to specific parameters• .X file reference for the same

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Design for Runtime Design for Runtime EfficiencyEfficiency• Compile effects into hardware Compile effects into hardware

friendly formatfriendly format• State blocks and push buffers

• Efficient setting of effect Efficient setting of effect parametersparameters• Can set parameters within effect

application• Integration with an optimizing Integration with an optimizing

language back endlanguage back end• Caching common parameter

combinations

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Unify Fixed and Unify Fixed and Programmable Programmable PipelinesPipelines• A consistent framework for A consistent framework for

programming shadersprogramming shaders• Fixed-function programming using

render states, texture stage state, fixed-function vertex processing

• Assembly level vertex and pixel shader programming

• Shading language based programming

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Unify Unify Cross-PlatformCross-Platform ProgrammingProgramming

• Techniques in an effect can span Techniques in an effect can span shader models (like VS 1.1, VS 2.0, shader models (like VS 1.1, VS 2.0, etc.)etc.)

• Unified parser allows handling the Unified parser allows handling the same effect file cross platformsame effect file cross platform• Only techniques that validate on runtime

platform available for actual use

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Effect-Language Effect-Language IntegrationIntegration• Techniques can call language functionsTechniques can call language functions

• This is where the back-end is specified• Same function can be used in multiple techniques

compiled to multiple back-ends

• Expressions of parameters can be used in Expressions of parameters can be used in state assignmentstate assignment

• Per-primitive expressions detected and Per-primitive expressions detected and optimized out by compiler when within an optimized out by compiler when within an effecteffect

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SpecializationSpecialization

• Specify constants that are to be Specify constants that are to be literalsliterals

• via ID3DXEffectCompiler Interfacevia ID3DXEffectCompiler Interface• Call CompileEffect() methodCall CompileEffect() method

• returns pre-optimized shader• Easily generate multiple shaders Easily generate multiple shaders

optimized for specific casesoptimized for specific cases• Can helps shader management by Can helps shader management by

generating them on the flygenerating them on the fly

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Linking Effects with Linking Effects with GeometryGeometry• .X file extensions to link effect with .X file extensions to link effect with

geometrygeometry• Enhance the notion of materials to include

effect files• Inline or external references

• Besides referencing effects, certain parameter values can be specialized in EffectInstance

• This is usually the artist tweakable ones

• D3DX API support for associating effects D3DX API support for associating effects with mesheswith meshes

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Fragment LinkerFragment Linker

• Efficiently links togetherEfficiently links together• HLL fragments• And asm fragments

• Current Features:Current Features:• Symbol table resolution• Register use optimization• Dead code removal

• via ID3DXFragmentLinker interfacevia ID3DXFragmentLinker interface

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Performance Performance • Compiler updates will be frequentCompiler updates will be frequent• Microsoft has good compiler peopleMicrosoft has good compiler people

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Current Back EndsCurrent Back Ends

• Vertex Shader 1.1, 2.0Vertex Shader 1.1, 2.0• Pixel Shader 1.1, 1.4, 2.0Pixel Shader 1.1, 1.4, 2.0

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SummarySummary

• HLSL abstraction solveHLSL abstraction solve•Continuing hardware evolution•Shader programming complexity

• API semantics solveAPI semantics solve•Shader interoperability

• D3DX Effects, specializers solveD3DX Effects, specializers solve•Combinatoric numbers of shaders

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SummarySummary

• HLSL is the next step in graphics HLSL is the next step in graphics API/hardware evolutionAPI/hardware evolution

• DirectX implementation providesDirectX implementation provides•Close API integration

•Semantic binding to low-level API•Shader management via D3DX effects•Full IDE support including debugging

•Performant cross vendor support

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• Check it out!Check it out!• Use it in your research Use it in your research

&development&development• Let us know what you thinkLet us know what you think

• directx@microsoft.com

Action ItemsAction Items

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QuestionsQuestions

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BackupBackup

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Unique FeaturesUnique Features

• Cleanly integrated with Direct3D Cleanly integrated with Direct3D APIAPI

• Run-time compilableRun-time compilable• Integrated with Effect FrameworkIntegrated with Effect Framework

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API IntegrationAPI Integration

• Co-designed with DirectX 9 APICo-designed with DirectX 9 API• Enables ease-of-use in apps and in Enables ease-of-use in apps and in

toolstools• Enables improved performanceEnables improved performance

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Run-Time CompilableRun-Time Compilable

• Enables CPU to construct and Enables CPU to construct and optimize shaders for GPU optimize shaders for GPU dynamicallydynamically

• Facilitates authoring tool/art Facilitates authoring tool/art pipelinepipeline•Enables dynamic content/titles