More GPU Programming and GPGPU

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More GPU Programming and GPGPU

• Chun-Fa Chang
• National Taiwan Normal University

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Calculator vs. Computer

• What is the difference between a calculator and a
  computer?
• Doesnt a compute-r just compute?
• The Casio fx3600p calculated can be programmed
  (38 steps allowed).

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Turing Machine

• Can be adapted to simulates the logic of any
  computer that could possibly be constructed.
• von Neumann architecture implements a universal
  Turing machine.
• Look them up at Wikipedia!

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Simplified View

• The Data Flow
• 3D Polygons (Colors, Lights, Normals, Texture
  Coordinatesetc.)
• 2D Polygons
• 2D Pixels (I.e., Output Images)

Transform ( Lighting)
Rasterization
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Global Effects
shadow
multiple reflection
translucent surface
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Local vs. Global
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How Does GPU Draw This?
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Quiz

• Q1 A straightforward GPU pipeline give us local
  illumination only. Why?
• Q2 What typical effects are missing?

Hint How is an object drawn? Do they consider
the relationship with other objects?
Shadow, reflection, and refraction
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• Wait but Ive seen shadow and reflection in games
  before

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Faked Global Illumination

• Shadow, Reflection, BRDFetc.
• In theory, real global illumination is not
  possible in current graphics pipeline
• Conceptually a loop of individual polygons.
• No interaction between polygons.
• Can this be changed by multi-pass rendering?

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Case Study Shadow Map

• Using two textures color and depth
• Relatively straightforward design using pixel
  (fragment) shaders on GPUs.

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Eyes View
Lights View
Depth/Shadow Map
Image Source Cass Everitt et al., Hardware
Shadow Mapping NVIDIA SDK White Paper
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Basic Steps of Shadow Maps

• Render the scene from the lights point of view,
• Use the lights depth buffer as a texture (shadow
  map),
• Projectively texture the shadow map onto the
  scene, ? Use TexGen or shader
• Use texture color (comparison result) in
  fragment shading.

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Adding Memory to the GPU Computation

• Modern GPUs allow
• The usage of multiple textures.
• Rendering algorithms that use multiple passes.

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GPU Shading Effects

• Reflection and refraction
• Relief on surface
• Ambient occlusion and lighting

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Real-Time Rendering of Splashing Water

• Particle system simulation for real-time
  interaction with terrains and dynamic objects.
• Reconstruction of the splash surface with 2D
  metaballs

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GPU Programming

• OpenGL offers a shading language since OpenGL
  2.0.
• NVIDIA offers Cg and CUDA (for GF8800)
• Cross-platform SH and RapidMind
• Currently support GPUs and CELL, may support
  multicore CPUs in the future.
• For more detail, see http//www.rapidmind.net/doc
  umentation.php

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NVIDIA Geforce 6800
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NVIDIA Geforce 8800