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Procedural Methods

Procedural Methods. A Brief Introduction. Introduction to Computer Graphics Arizona State University Dianne Hansford. Procedural Methods (PM). Methods to model or render physically-based phenomena textures: wood, marble, .. M. Agrawala, Stanford. Procedural Methods (PM).

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Procedural Methods

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  1. Procedural Methods A Brief Introduction Introduction to Computer Graphics Arizona State University Dianne Hansford

  2. Procedural Methods (PM) • Methods to model or render physically-based phenomena • textures: wood, marble, .. M. Agrawala, Stanford

  3. Procedural Methods (PM) • Methods to model or render physically-based phenomena • textures: wood, marble • gases: clouds, smoke, fog, ...David Ebert, Purdue

  4. Procedural Methods (PM) • Methods to model or render physically-based phenomena • textures: wood, marble, .. • gases: clouds, smoke, fog, ... • modeling: trees, implicit surfaces, ...SpeedTree CAD

  5. Procedural Methods (PM) • Methods to model or render physically-based phenomena • textures: wood, marble • gases: clouds, smoke, fog, ... • modeling: trees, implicit surfaces, ... • animationDave McAllister, UNC

  6. History • mid ’80s: realistic textures (marble, wood) • mid ’80s: water, smoke, steam, fire, tribbles(Wrath of Khan), plants • ’89: Pixar’s Renderman expanded use of PM • important developments for real-time PM: 1) increased CPU power2) powerful and programmable GPUs available in affordable PCs and game consoles

  7. PM Definition Algorithms to build representations of underlying phenomenaSpecify some characteristic of a computer-generated model or effectExample: marble (texture) color from math functions/algorithms rather than scanned-in

  8. Need? • Surface (polygonal) model approach main focus of this class, however ... • Physical objects (clouds, smoke, water) demand a different type of modeling complexity, changing state, dynamics, randomness, ....

  9. Advantages of PM • Abstraction:Develop details as neededMultiresolution models generate polygons only as neededAlso known as Level of Detail (LOD) Example: Trees – number of polygons depends on screen space area used Storage savings Time requirements for programmer to generate data

  10. Advantages of PM • Parametric control:Scalar values control complex shape definitionexample: roughness of a mountain frees programmer from low-level controlstochastic procedures can produce in interesting, unexpected results Created by Tim Stain, SciFi

  11. Advantages of PM • Flexibility Capture essence of object, phenom, motion without being constrained by complex laws of physics Can achieve natural laws or artistic effects Physically-based modeling of polygonal objects can be difficult Obey physical laws  lots of programming and mathAvoiding unnatural self-intersections is expensive

  12. PM: 2 Examples • Particle SystemsCollection of particles whose behavior determined by solution of differential eqns Physically-based modeling from some physics + constraints • FractalsCapitalize on self-similarity of nature

  13. Particle Systems Nice site:University of North Carolina, David McAllister http://www.cs.unc.edu/~davemc/Particle/ Nice class notes:CMU, Doug James http://www-2.cs.cmu.edu/~djames/15-462/Fall03/notes/13-particleSystems.pdf

  14. Fractals Fractals: self-similar (identical), infinitely “long” http://math.rice.edu/~lanius/fractals/WHY/ Julia sets and Mandelbrot sets http://aleph0.clarku.edu/~djoyce/julia/julia.html Fractal mountains http://www.gameprogrammer.com/fractal.html http://world.std.com/~bgw/applets/1.02/MtFractal/MtFractal.html http://www.sci.fi/~timstain/english/gallery/fractal.htm http://www.perlentraum.de/undina1/fractal_mountain.htm

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