1. A Crash Course on Programmable Graphics Hardware
Li-Yi Wei
2005
at Tsinghua University, Beijing

2. Why do we need graphics hardware?

3. The evolution of graphics hardware
SGI Origin 3400
NVIDIA Geforce 7800

4. 7 years of graphics
accelenation.com/?doc=123&page=1

5. Ray tracing General & flexible Intuitive Global illumination
Hard to accelerate

6. Polygonal graphics pipeline
Local computation
Easy to accelerate
Not general
Unintuitive

7. Graphics hierarchy Layered approach Encapsulation Protection
Like network layers
Encapsulation
Easy programming
Driver optimization
Driver workaround
Driver simulation
Protection
Hardware error check

8. Overview Graphics pipeline GPU programming
Only high level overview (so you can program), not necessarily real hardware
GPU programming

9. Graphics pipeline

10. Application Mostly on CPU High level work User interface Control
Simulation
Physics
Artificial intelligence

11. Host Gatekeeper of GPU Command processing Error checking
State management
Context switch

12. Geometry Vertex processor Primitive assembly Clip & cull
Viewport transform

13. Vertex Processor Process one vertex at one time Programmable
No information on other vertices
Programmable
Transformation
Lighting

14. Transformation
Global to eye coordinate system

15. Lighting
Diffuse
Specular

16. Transform & Light on Vertex Processor
A sequence of assembly instructions
(more on this later)

17. Primitive Assembly
Assemble individual vertices into triangle (or line or point)
Performance implication
A triangle is ready only when all 3 vertices are
Vertex coherence & caching

18. Clipping & Culling Backface culling Clipping against view frustum
Remove triangles facing away from view
Eliminate ½ of the triangles in theory
Clipping against view frustum
Triangles may become quadrilaterals

19. Viewport transform
From floating point range [-1, 1] x [-1, 1] to integer range [0, height-1] x [0, width-1]

20. Rasterization Convert primitives (triangles, lines) into pixels
Barycentric coordinate
Attribute interpolation

21. Triangles into pixels

22. Attribute interpolation
Barycentric

23. Perspective correct interpolation
incorrect
correct

24. Fragment processor
Fragment: corresponds to a single pixel and includes color, depth, and sometimes texture-coordinate values.
Compute color and depth for each pixel
Most interesting part of GPU

25. Texture Optional Cache data Sampling/filtering (though hard to avoid)
Hide latency from FB
Sampling/filtering
I told you this last time

26. ROP (Raster Operation)
Write to framebuffer
Comparison
Z, stencil, alpha, window

27. Framebuffer Storing buffers and textures Connect to display
Characteristics
Size
Bandwidth
Latency

28. Conceptual programming model
Inputs (read-only)
Attributes
Constants
Textures
Registers (read-write)
Used by shader
Outputs (write-only)

29. Simple example HPOS: position COL0: diffuse color
MOV o[HPOS], v[HPOS];
MOV o[COL0], v[COL0];

30. More complex example o[COL0] = v[COL0] + constant*v[HPOS];
MOV o[HPOS], v[HPOS];
MOV R0, v[COL0];
MAD R0, v[HPOS], c[0], R0;
MOV o[COL0], R0;

31. Sample instruction set

32. A real example

33. High-level shading language
Writing assembly is
Painful
Not portable
Not optimize-able
High level shading language solves these
Cg, HLSL

34. Cg example

35. Applications Too many of them for me to describe here
The only way to learn is try to program
Useless for you even if I try to describe
Look at developer website
NVIDIA, ATI, GPGPU

36. Homework Try to program GPU! Stanford course on graphics hardware
Even without NVIDIA GPU, you can download the emulator
Stanford course on graphics hardware
History of graphics hardware
7 years of graphics
accelenation.com/?doc=123&page=1