Shading Languages

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Shading Languages

• Yung-feng Chiu

2
Agenda

• Introduction
• Pixars RenderMan, MSs HLSL, NVs CgFX, ATIs
  RenderMonkey
• Demos
• .fx file
• Comparsion

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Key Idea of a Shading Language

• Image synthesis can be divided into two basic
  concerns
• Shape Geometric Objects, Coordinates,
  Transformations, Hidden-Surface Methods
• Shading Light, Surface, Material, Texture,
• Control shading not only by adjusting parameters
  and options, but by telling the shader what you
  want it to do directly in the form of a procedure

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Pixars RenderMan

• Separation of Modeling and Rendering
• RenderMan serves as the interface.
• Scene Shape Shading
• The power of RenderMan is in the shading part.

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Pixars RenderMan -2
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RenderMans RIB File Structure
Options global to the entire animation Options global to the entire animation Options global to the entire animation
Frame Block Frame Block
Image options Camera options
World Block Attributes, lights, primitives
Changed Options
Another world block
Next frame block Next frame block
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RenderMans Shader

• Phong shader

surface phong( float Ka 1, Kd 1, Ks
0.5 float roughness 0.1 color
specularcolor 1 ) normal Nf
faceforward( normalize(N), I ) vector V
-normalize(I) color C 0 illuminance( P
) vector R 2normalize(N)
(normalize(N) . normalize( L )) -
normalize( L ) C KaCs
KdCs( normalize(N) . normalize(L) )
Ksspecularcolor pow(( R . V ), 10)
Ci CCs
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RenderMans Shader -2

• Attaching to the RIB file

AttributeBegin Translate 0 -1.5
0 Rotate 20 0 0 1 Color 0.8 0.0 0.0 Surface
"phong" "Ka" .1 "Kd" .8 "Ks" 1
"roughness" 0.1 "specularcolor" 1 1 1 Basis
"bezier" 3 "bezier" 3 PatchMesh "bicubic" 13
"nonperiodic" 10 "nonperiodic" "P" 1.5 0 0 1.5
0.828427 0 0.828427 1.5 0 0 1.5 0 -0.828427 1.5 0
-1.5 0.828427 0 -1.5 0 0 -1.5 -0.828427 0
-0.828427 -1.5 0 0 -1.5 0 0.828427 -1.5 0 1.5
-0.828427 0 1.5 0 0 1.5 0 0.075 1.5 0.828427
0.075 0.828427 1.5 0.075 0 1.5 0.075 -0.828427
1.5 0.075 -1.5 0.828427 0.075 -1.5 0 0.075 -1.5
-0.828427 0.075 -0.828427 -1.5 0.075 0 -1.5 0.075
0.828427 -1.5 0.075 1.5 -0.828427 0.075 1.5 0
0.075 2 0 0.3 2 1.10457 0.3 1.10457 2 0.3 0 2 0.3
-1.10457
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Misrosofts HLSL (.fx)

• Assembly
• dp3 r0, r0, r1
• max r1.x, c5.x, r0.x
• pow r0.x, r1.x, c4.x
• mul r0, c3.x, r0.x
• mov r1, c2
• add r1, c1, r1
• mad r0, c0.x, r1, r0
• ...

HLSL float4 cSpec pow(max(0, dot(Nf, H)),
phongExp).xxx float4 cPlastic Cd (cAmbi
cDiff) Cs cSpec

• Simple Blinn-Phong shader expressed in both
  assembly and HLSL

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nVidias CgFX Overview
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nVidias CgFX Overview -2

• Supports Microsoft .fx files
• Cg plus
• Multi-pass
• Hardware fallbacks (techniques)
• Complete Hardware states
• Tweakables
• MS .fx plus
• DirectX8 and OpenGL

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nVidias CgFX Overview -3

• CgFX (.fx)
• Manages whole rendering process
• Handles render states cross API support
• Convenient exposure of tweakables artist
  controls
• Cg Shaders (.cg)
• semantics directives to match your C and other
  custom hardware shaders
• Bind textures/parameters to specific HW registers
• Cg Runtime
• Thin API to compile on demand at runtime
• Optimizes manages .Cg for range of target HW

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nVidias CgFX Viewer
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nVidias CgFX Viewer -2

• Scene graph GUI
• .fx parameters edition
• Error reporting for easy .fx file problem
  identification
• Runs OpenGL, DirectX8, DirectX9
• Switch between devices at any point

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Production Pipeline with CgFX
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ATIs RenderMonkey
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ATIs RenderMonkey -2

• Try to solve some of the problems developers face
  when designing software on emerging hardware
• Create a flexible, extensible shader development
  environment that allows easy incorporation of
  existing APIs
• Support for low level DirectX8/9 in the current
  version
• Extensible framework to support emerging HLSL
  standards
• DirectX9 HLSL
• OpenGL 2.0 Shading Language
• RenderMan
• Maya Shade Trees

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ATIs RenderMonkey -3

• Encapsulate all effect data in a single XML text
  file
• Each Effect Workspace consists of
• Effect Group(s)
• Effect(s)
• Pass(es)
• Render state
• Pixel Shader
• Vertex Shader
• Geometry
• Textures
• Variables and stream mapping nodes

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Demos !
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Bump Map Example

• Bump mapping simulates detail with a surface
  normal that varies across a surface

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RenderMan Example
displacement lumpy ( float Km 1, frequency 1,
maxoctaves 6 string shadingspace
"shader" float truedisp 1)
point Pshad transform (shadingspace,
frequencyP) float dPshad
filterwidthp(Pshad) float magnitude fBm
(Pshad, dPshad, maxoctaves, 2, 0.5) N
Displace (normalize(N), shadingspace,
Kmmagnitude, truedisp)
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Pixel Shader Example
ps.1.1 tex t0 // base map tex t1 // bump
map tex t2 // light vector from normalizer
cube map dp3_sat r1, t1_bx2, t2_bx2 //
N.L mul r1, r1, c0 // N.L
diffuse_light_color mul_sat r0, t0, r1 // (N.L
diffuse_light_color) base
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Cg Example
f2fb DiffuseBumpPS(v2f IN, uniform sampler2D
DiffuseMap, uniform sampler2D NormalMap,
uniform float4 bumpHeight) f2fb OUT float4
color tex2D(DiffuseMap) //fetch base
color //fetch bump normal float4 bumpNormal
expand(tex2D(NormalMap)) bumpHeight //expand
iterated light vector to -1,1 float4
lightVector expand(passthrough(IN.LightVector))
//compute final color (diffuse
ambient) float4 bump uclamp(dot3_rgba(bumpNorma
l.xyz, lightVector.xyz)) OUT.col color
bump return OUT
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Fixed Function Example
Texture0 ltnormalMapgt Target0
Texture2D MinFilter0 Linear MagFilter0
Linear MipFilter0 Linear Texture1
ltdiffuseTexturegt Target1 Texture2D MinFilter
1 Linear MagFilter1 Linear MipFilter1
Linear
ColorOp0 DotProduct3 AlphaOp0
SelectArg1 ColorArg10 Texture ColorArg20
Diffuse AlphaArg10 Texture AlphaArg20
Diffuse ColorOp1 Modulate ColorArg11
Current ColorArg21 Texture AlphaOp1
SelectArg1
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GL2 Logical Diagram
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OpenGLFixed Function Vertex
Vertex (object)
Vertex (clip)
TransformMVP,MV,MV-T
Normal
Vertex (eye)
ColorSecondaryColor
FrontBackColor
0,1
Lighting
FrontBackSecondaryColor
0,1
Texgen
TextureMatrixn
TexCoordn
TexCoordn
EdgeFlag
EdgeFlag
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GL2 Vertex Processor
Vertex (object)
Vertex (clip)
Uniform
Normal
Vertex (eye)
ColorSecondaryColor
VertexShader
FrontBackColor
FrontBackSecondaryColor
Temporaries
TexCoordn
TexCoordn
EdgeFlag
EdgeFlag
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OpenGLFixed Function Fragment
Color
SecondaryColor
Texn
TEn
Sum
Fog
Color
TexCoordn
0,1
z (ze,f )
Depth
Depth
Coord
Coord
FrontFacing
FrontFacing
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GL2 Fragment Processor
Color
Uniform
Texture
SecondaryColor
FragmentShader
TexCoordn
Color
z (ze,f )
Depth
Depth
Temporaries
Coord
Coord
FrontFacing
FrontFacing
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Using FX in Your Application

• Load effect
• Validate technique for hardware
• Detect parameters for technique
• Render Loop (for each object in scene)
• Set technique for the object
• Set parameter values for technique
• For each pass in technique
• Set state for pass
• Draw object

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Using FX The FX API

• LPD3DXBUFFER pError NULL
• D3DXCreateEffectFromFile(m_pd3dDevice,
  _T("simple.fx"), NULL, NULL, 0, NULL, m_pEffect,
  pError)
• SAFE_RELEASE(pError)
• . . .
• UINT iPass, cPasses
• m_pEffect-gtSetTechnique(Simple")
• m_pEffect-gtSetVector(var1", v)
• m_pEffect-gtBegin(cPasses, 0)
• for (iPass 0 iPass lt cPasses iPass)
• m_pEffect-gtPass(iPass)
• m_pMesh-gtDraw()
• m_pEffect-gtEnd()

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Effect File Structure

• An effect is made up of multiple rendering
  algorithms (techniques) each made up of one or
  more passes
• Effect File Structure
• Variable declarations
• Technique 1
• Pass 1
• Pass n
• Technique n
• Pass 1
• Pass n

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.fx file
float4x4 worldMatrix World // World or model
matrix float4x4 mvpMatrix WorldViewProjection /
/ Model View Projection float4x4
worldViewMatrix WorldView // World
View texture diffuseTexture DiffuseMap //
Diffuse Map semantic lt string File
"default_color.dds" // Default texture file
annotation gt texture normalMap NormalMap //
Normal Map semantic lt string File
"default_bump_normal.dds"// Default texture file
annotation gt float4 ambientColor Ambient lt gt
0.1, 0.1, 0.1, 1.0 float bumpHeight lt
// GUI annotations string gui "slider"
float min 0 float max 1 float step
0.1 gt 0.5
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.fx file

• void DiffuseBumpVS(float4 Position POSITION, //
  Position in object space
• float2 TexCoord TEXCOORD0,// Texture
  coordinates
• out float4 TexCoord0 TEXCOORD0, // Texture
  coordinates
• out float4 Position POSITION)// Position in
  projection space
• TexCoord0.xy IN.TexCoord.xy // Pass texture
  coordinates for the diffuse map
• Position mul(WorldViewProj, IN.Position)//
  Compute position in projection space
• void DiffuseBumpPS(float4 Position POSITION, //
  Position in projection space
• out float4 col COLOR)
• float4 color tex2D(DiffuseMap, UV) // Look up
  the diffuse map
• col color light // Modulate the diffuse
  color by the light

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.fx file

• sampler2D diffuseSampler sampler_state
• Texture ltdiffuseTexturegt
• MinFilter Linear
• MagFilter Linear
• MipFilter Linear
• sampler2D normalSampler sampler_state
• Texture ltnormalMapgt
• MinFilter Linear
• MagFilter Linear
• MipFilter Linear
• technique CgTechnique // Both the vertex and the
  fragment shaders are in Cg
• pass p0
• ZEnable true
• ZWriteEnable true
• CullMode None

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Cg Pipeline
Graphics programs are written in Cg ...
Cg Runtime API
... and compiled to ...
... low-level assembly code ...
... that runs on any GPU compatible with DirectX
or OpenGL
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Using the Cg Compiler
Application Development
Your Application
// // Diffuse lighting // float d
dot(normalize(frag.N), normalize(frag.L)) if (d
lt 0) d 0 c df4tex2D(t, frag.uv)diffuse
Cg program source code

1. Load/bind program
2. Specify program parameters
3. Specify vertex inputs
4. Render

Cg Compiler
DP3 r0.x, fTEX0, fTEX0 RSQ r0.x, r0.x MUL
r0, r0.x, fTEX0 DP3 r1.x, fTEX1,
fTEX1 RSQ r1.x, r1.x MUL r1, r1.x,
fTEX1 DP3 r0, r0, r1 MAX r0.x, r0.x, 1.0 MUL
r0, r0.x, DIFFUSE TEX r1, fTEX1, 0, 2D MUL
r0, r0, r1
Shader program assembly code
Shader Compiler (nvasm.exe, psa.exe)
Shader Binary
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Typical Production Pipeline
Artists create models, textures, maps, in DCC
tool of choice
Programmerswrite assembly for different hardware
DCC tool (Maya, Max, SoftImage, )
Scene exporter plug-in
Not the same!
Models, Textures, Maps,
Application (game, renderer, )
Scene manager
App Scene Manager hard-coded to choose at
run-time the appropriate ASM shaders state for
the hardware
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FX-Enabled Production Pipeline
Artists assign FX files to scene objects and
tweak parameters for each object in real-time
Programmers and/or artists write FX effects
DCC tool (Maya, Max, SoftImage, )
FX material plug-in
Scene exporter plug-in
Same Image!
Models, Textures, Maps, FX effects parameters
Application (game, renderer, )
Scene manager
For any FX, App Scene Manager chooses at
run-time the appropriate technique for the
hardware
FX runtime
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Comparison