1. Programmable Shaders
Dr. Scott Schaefer

2. Graphics Cards Performance
Nvidia Geforce 6800 GTX1
6.4 billion pixels/sec
Nvidia Geforce 7900 GTX2
15.6 billion pixels/sec
Xbox 3603
16 billion pixels/sec (4X AA)
Nvidia Geforce 8800 GTX4
36.8 billion pixels/sec
Nvidia Geforce GTX 2955
92.2 billion pixels/sec 1: 2: 3: 4: 5:

3. Parallel Processing Power
Nvidia Geforce Titan Z
5760 programmable processors
876 MHz each
672 GB/s memory bandwidth
12 GB memory

4. Parallel Processing Power
AMD’s Radeon R9 295X processors, 11.5 TFLOPS
IBM’s ASCI White cores, 12.2 TFLOPS Fastest Computer in the World 2001

5. Graphics Pipeline
Vertices

6. Transformation/Lighting
Graphics Pipeline
Vertices
Vertex
Transformation/Lighting

7. Transformation/Lighting
Graphics Pipeline
Vertices
Vertex
Transformation/Lighting
Transformed Vertices

8. Transformation/Lighting Viewport Transformation
Graphics Pipeline
Vertices
Vertex
Transformation/Lighting
Transformed Vertices
Viewport Transformation

9. Transformation/Lighting Viewport Transformation
Graphics Pipeline
Vertices
Vertex
Transformation/Lighting
Vertex Index Stream
Transformed Vertices
Viewport Transformation
Triangle Setup

10. Transformation/Lighting Viewport Transformation
Graphics Pipeline
Vertices
Vertex
Transformation/Lighting
Vertex Index Stream
Transformed Vertices
Viewport Transformation
Triangle Setup
Backface Culling

11. Transformation/Lighting Viewport Transformation
Graphics Pipeline
Vertices
Vertex
Transformation/Lighting
Vertex Index Stream
Transformed Vertices
Viewport Transformation
Triangle Setup
Backface Culling
Clipping

12. Graphics Pipeline Vertices Vertex Index Stream Transformed Vertices
Transformation/Lighting
Vertex Index Stream
Transformed Vertices
Viewport Transformation
Triangle Setup
Backface Culling
Clipping
Interpolation/Rasterization

13. Graphics Pipeline Vertices Vertex Index Stream Transformed Vertices
Transformation/Lighting
Vertex Index Stream
Transformed Vertices
Viewport Transformation
Triangle Setup
Backface Culling
Clipping
Interpolation/Rasterization
Pixel Location/Color/Depth

14. Graphics Pipeline Vertices Vertex Index Stream Transformed Vertices
Transformation/Lighting
Vertex Index Stream
Transformed Vertices
Viewport Transformation
Triangle Setup
Backface Culling
Clipping
Interpolation/Rasterization
Pixel Location/Color/Depth
Visibility Determination

15. Graphics Pipeline Vertices Vertex Index Stream Transformed Vertices
Transformation/Lighting
Vertex Index Stream
Transformed Vertices
Viewport Transformation
Triangle Setup
Backface Culling
Clipping
Interpolation/Rasterization
Pixel Location/Color/Depth
Visibility Determination
Frame Buffer

16. Programmable Graphics Pipeline
Vertices
Vertex Shader
Vertex Index Stream
Transformed Vertices/
Normals/Texture coords/…
Viewport Transformation
Triangle Setup
Backface Culling
Clipping
Interpolated
Vertex Data
Interpolation/Rasterization
Pixel Shader
Pixel Location
Visibility Determination
Color/Depth
Frame Buffer

17. Shader Programming Many different languages Assembly
OpenGL Shading Language
Nvidia’s CG
Microsoft’s HLSL
Different capabilities based on shader model
Register count
Instructions
Maximum number of instructions

18. Vertex Shaders Input: anything associated with vertices
Position, normal, texture coordinates, etc…
Output: transformed vertices
MUST output position
Can produce color, normal, texture coordinates, etc…

19. Vertex Shaders // vertex shader output structure struct VS_OUTPUT {
float4 Pos : POSITION; };

20. Vertex Shaders VS_OUTPUT VS(
float3 InPos : POSITION // Vertex position in model space ) {
VS_OUTPUT Out = (VS_OUTPUT)0;
// transform the position
float3 transformedPos = mul(float4(InPos, 1), (float4x3)World);
Out.Pos = mul(float4(transformedPos,1), ViewProjection);
return Out; }

21. Pixel Shaders Input: Vertex data produced from vertex shader Output:
MUST output color
Can output depth as well
Cannot change location of pixel on screen

22. Pixel Shaders float4 PS ( VS_OUTPUT In ) : COLOR {
// may perform texture lookup, depth effects, fog, etc…
return float4 ( 1, 1, 1, 1 ); }

23. Gouraud Shading Example
// vertex shader output structure
struct VS_OUTPUT {
float4 Pos : POSITION;
float4 Color : COLOR; };

24. Gouraud Shading Example
VS_OUTPUT VS(
float3 InPos : POSITION, // Vertex position in model space
float3 InNormal : NORMAL // Vertex normal in model space ) {
VS_OUTPUT Out = (VS_OUTPUT)0;
// transform the position and normal
float3 transformedPos = mul(float4(InPos, 1), (float4x3)World);
Out.Pos = mul(float4(transformedPos,1), ViewProjection);
float3 transNormal = mul(InNormal, (float3x3)World); // normal (view space)
Out.Color = float4 ( calcColor ( normalize ( lightPos – transformedPos ), transNormal,
normalize ( eyePos – transformedPos ) ), 1 );
return Out; }

25. Gouraud Shading Example
float3 calcColor ( float3 lightVec, float3 normal, float3 eyeToVertex ) {
float3 color = 0;
color += lightColor * MaterialAmbient;
color += lightColor * MaterialDiffuse * max ( 0, dot ( normal, lightVec ) );
float3 R = normalize ( reflect ( lightVec, normal ) );
color += lightColor * MaterialSpecular * pow ( max ( 0, dot ( R,
eyeToVertex ) ), MaterialSpecularPower );
return color; }

26. Gouraud Shading Example
float4 PS ( VS_OUTPUT In ) : COLOR {
return In.Color; }

27. Phong Shading Example // vertex shader output structure
struct VS_OUTPUT {
float4 Pos : POSITION;
float3 Normal : TEXCOORD0;
float3 TransformedPos : TEXCOORD1; };

28. Phong Shading Example VS_OUTPUT VS(
float3 InPos : POSITION, // Vertex position in model space
float3 InNormal : NORMAL // Vertex normal in model space ) {
VS_OUTPUT Out = (VS_OUTPUT)0;
// transform the position and normal
Out.TransformedPos = mul(float4(InPos, 1), (float4x3)World);
Out.Pos = mul(float4(Out.TransformedPos,1), ViewProjection);
Out.Normal = mul(InNormal, (float3x3)World); // normal (view space)
return Out; }

29. Phong Shading Example float4 PS ( VS_OUTPUT In ) : COLOR {
// vector from vertex towards eye
float3 EyeToVertex = normalize ( In.TransformedPos - EyePos );
float3 normal = normalize ( In.Normal );
float4 color = calcColor ( normalize ( lightPos – In.TransformedPos ), normal,
EyeToVertex );
return color; }

30. General Purpose GPU Programming
Originally success was limited because problems had to be crammed into graphics pipeline
General purpose computation now available
Nvidia’s CUDA
DirectX Compute
OpenCL