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The Future of Graphics Hardware: Programmability

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The results of one shading program can be interpreted as the ... Data. Partial. Results. New Things to do with Vertex Programs and Pixel Shaders (Automatic! ... – PowerPoint PPT presentation

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Title: The Future of Graphics Hardware: Programmability


1
The Future of Graphics Hardware Programmability
David B. Kirk Chief Scientist
2
The Near Future
A Revolution in Graphics Hardware
  • We now have full hardware OpenGL 1.3 and DirectX
    8 pipelines
  • Moving from graphics accelerators to GPUs
  • Next multiple programmable processors

3
Programmability Changes the World
  • graphics hardware pipelines are becoming
    massively programmable
  • will fundamentally change graphics
  • allows hyper-realistic characters, special
    effects, and lighting and shading

4
Why are Movies and Special Effects Exciting and
Interesting?
  • Suspension of Disbelief
  • Something amazing is happening
  • But, you believe it, because it is real
  • Realistic and detailed characters
  • Motion, and emotion
  • Realistic and recognizable materials
  • Chrome looks like chrome
  • Skin looks like skin
  • Action!

5
3D Graphics is about
  • Animated films (Final Fantasy, Toy Story, etc.)
  • Special Effects in live action movies (The
    Matrix)
  • Interactive Entertainment (games! -)
  • Computer Models of real world objects
  • Or, objects that havent been invented yet
  • Making reality more fantastic
  • Making fantasies seem real

6
Live action sfx slide
Programmability Bridges the Gap between Movies
and Interactivity
7
The DirectX7 Graphics Pipeline (GeForce/GeForce2)
vertex transform and lighting
T L
setup
rasterizer
texture
per
-
pixel texture
blending
fb
anti-alias
8
3D Movie Special Effects Come to PC and Console
Graphics
  • Lots of Geometry ? 1,000,000 polygons/frame!
  • Geforce does this hardware Transform Lighting
  • GeForce3 makes the pipeline programmable
  • Lots of Lighting and Shading
  • Geforce (year 2000)
  • Hardwired vertex lighting
  • Little shader programs run for every pixel
  • Taking Shading to the next level (GeForce3)
  • Powerful vertex programs run for every vertex
  • Powerful shader programs run for every pixel

9
The DirectX8 Graphics Pipeline (GeForce3)
curved
surfaces
vertex
programmable
shaders
per
-
vertex processing
setup
rasterizer
tex
-
addr
shadows
ops
tex
3d
texture
programmable
blending
per
-
pixel shading
fb
antialias
10
Developers Have Been Asking For…
  • Complete control of the transformation and
    lighting hardware
  • Complex vertex operations performed in hardware
  • Custom vertex lighting
  • Custom skinning and blending
  • Custom texgen
  • Custom texture matrix operations
  • ltyour request goes heregt

11
Custom Substitute for Standard TL
Vertex Input
  • Constant Memory

16 entries
Registers
ProgrammableVertex Processor
addr
addr
A0
data
data
128 instructions
12 entries
Vertex Output
96 entries
13 entries
12
What does it do?
  • Per vertex calculation
  • Processing of
  • Colors true color, pseudo color
  • 3D coordinates - procedural geometry, blending,
    morphing, deformations
  • Texture coordinates texgens, set up for pixel
    shaders, tangent space bumpmap setup
  • Fog elevation based, volume based
  • Point size
  • Vertex program accepts one input vertex,
    generates one output vertex

13
Aggressive use of Vertex Programs is SAFE and
IMPORTANT
  • Its safe to use vertex programs pervasively
  • Many hardware platforms have them
  • Mainstream GPUs will have them this fall
  • CPUs can emulate vertex shaders adequately, so
    CPU fallback is OK
  • Its important to design content for vertex and
    pixel shaders
  • Adopt vertex and pixel programming, and author
    content from the top-down
  • Its much MUCH easier to scale down and fallback
    than to scale up

14
Programmable Shaders make possible materials l
ighting reflections shadows
15
Evolution of Hardware Shading
  • Hardware Rasterizers and perspective-correct
    texture mapping (Voodoo / RIVA 128)
  • Single Pass Multitexture (Voodoo2 / TNT / TNT2)
  • Register Combiners a generalization of
    multitexture (GeForce 256)
  • Per-pixel Shading (Geforce2 GTS)
  • Programmable Hardware Pixel Shading (GeForce3)

16
Single Texture Programming Model
Source
Texture Blender
Texture 0
Result
17
Register Combiner Programming Model
Texture Combiner
Source(s)
Texture 0
Registers
Texture 1
Result(s)
18
Pixel Shading Pipeline
Triangle Rasterizer
8 Combiner Stages
ROP Frame buffer
Specular / fog Combiner
4 Pixel Shader Stages
19
Pixel Shaders
A pixel shader converts a set of texture
coordinates (s, t, r, q) into a color ( ARGB ),
using a shader program.
  • Pixel shaders use
  • Floating point math
  • Texture lookups
  • Results of previous pixel shaders

20
Simple Dependent Textures
  • The results of one shading program can be
    interpreted as the texture coordinates for a
    subsequent texture lookup.
  • AR ? ( s, t )
  • GB ? ( s, t )
  • Texture lookups become arbitrary
    functions.

Triangle Rasterizer
4 Pixel Shader Stages
21
Register Combiners / Texture Blending
  • Strict superset of framebuffer alpha blending
    capabilities
  • abcd
  • Register-based programming
  • All textures and colors available for each and
    every texture blending stage
  • 8 Stages
  • Signed color arithmetic

22
A processor model for Per-pixel Shading
  • Computation primitives
  • Texture addressing
  • Cube maps
  • Volume textures
  • Comparison muxery
  • Register combiners
  • Vector math (dot3, reflection, etc)
  • Hardware shading is now
  • Programmable
  • Extensible

23
Bigger Opportunities than TL and Multi-texture
  • Can do vertex transformation, n-bone skinning,
    texture coord generation, custom fog, lighting,
    shadows, lightmaps, etc…
  • PLUS, A complex rendering technique can be
    "factored" into components executed on CPU,
    vertex shader, and pixel shader
  • The true power of programmable vertex and pixel
    processing lies in the programmers ability to
    map more complex and varied algorithms onto the
    hardware

24
Instead of...
CPU
  • CPU does
  • Game code
  • AI
  • Physics
  • Scene management
  • GPU does
  • TL
  • Rasterization
  • Texturing / Shading
  • Drawing

Triangles Textures
Triangles Textures
GPU
Pixels
25
Think in terms of...
CPU
  • Higher level algorithms are mapped across both
    CPU GPU
  • CPU still does
  • Game code, AI, Physics, Scene management
  • GPU still does
  • TL, Rasterization, Texturing / Shading, Drawing
  • And, MORE

Partial Results
Partial Results
Data
GPU
Pixels
26
New Things to do with Vertex Programs and Pixel
Shaders
  • (Automatic!!!) Shadow Volume Generation for
    Stencil Shadows
  • Order-independent Transparency (Depth Peeling)
  • Motion Blur / Depth of Field

27
(No Transcript)
28
Order-Independent Transparency Good… Bad.
29
Order-Independent Transparency (Depth Peeling)
  • The algorithm uses an implicit sort to extract
    multiple depth layers
  • First pass render finds front-most fragment
    color/depth
  • Each successive pass render finds (extracts) the
    fragment color/depth for the next-nearest
    fragment on a per pixel basis
  • Use dual depth buffers to compare previous
    nearest fragment with current
  • Second depth buffer used for comparison (read
    only) from texture

30
Layer 0
Layer 1
Layer 2
Layer 3
31
(No Transcript)
32
Using Vertex Programs/Pixel Shaders to do Motion
Blur Depth of Field
33
Future Graphics Pipeline
host interface
smart memory interface
per
-
primitive and
primitives
per
-
vertex programs
setup
rasterizer
tex
-
addr
shadows
ops
3d
tex
texture
per
-
pixel shading
blending
frame buffer
anti-alias
34
Acknowledgements
  • Thanks to John Carmack, Sim Dietrich, Matthew
    Papakipos, Simon Green, Cem Cebonoyan, Erik
    Lindholm, Doug Rogers, Cass Everitt, Rui Bastos,
    Mark Kilgard, Greg James, Matthias Wloka, (and
    others I forgot!) for contributing ideas, slides,
    demos, and images.
  • Demo/Example source code and more whitepapers can
    be found at
  • http//www.nvidia.com/developer

35
Questions?
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