Artificial Evolution for Computer Graphics Karl Sims, SIGGRAPH 91 - - PowerPoint PPT Presentation

Artificial Evolution for Computer Graphics

Karl Sims, SIGGRAPH ‘91

Basic Idea

• To apply evolutionary techniques of

variation and selection to create complex simulated structures, textures and motions

Why artificial evolution?

• More use of Procedural Models in Computer

Graphics to create high degrees of complexity

• Procedure must be conceived, understood

and designed by a human

• Artificial evolution permits the creation of a

large variety of complex entities which do not require the user to understand the underlying creation process involved

Complex simulated structures, textures and motions

• 3D Plant Structures
• Volume Textures
• Animations

Evolutionary Concepts

• Genotype

genetic information codes for the creation of an individual

• Phenotype

the individual itself, the form that results from the developmental rules and the genotype

• Selection

determined by the fitness of the phenotype, parent selection and survival selection, non- random

• Reproduction

sexual, asexual, variation/mutation, random

Evolutionary Techniques

• Plant generation algorithms -- exploring

parameter spaces parameters describing fractal limits, branching factors, scaling, stochastic contributions Mutate and Mate parameter sets

• Genetic Algorithms -- Symbolic Lisp

expressions as genotype

symbolic expressions as genotype

• Genotype -- Lisp expressions which can

calculate a color for each pixel(x,y) are evolved using a function set containing proper

• perations (tree structure)
• For example:

(round (log (+ y (color-grad (round (+ (abs (round (log (+ y (color-grad (round (+ y (log (invert y) 15.5)) x) 3.1 1.86 #(0.95 0.7 0.59) 1.35)) 0.19) x)) (log (invert y) 15.5)) x) 3.1 1.9 #(0.95 0.7 0.35) 1.35)) 0.19) x)

Genetic Algorithms

• 1. Population size: 100 to 1000 or more
• 2. Selection: interactive selection
• 3. Fitness Evaluation: decided by users
• 4. Crossover and Mutation: dependent
• n probability

A simple flow chart

Results

• 3D Plant Structures (Figure 2, Figure 3)
• Volume Textures (Figure 5, Figure 6)
• Animations (Figure 7)

Future work

To automatically evolve a symbolic expression that could generate a specific goal image. Fitness evaluation becomes important.