(Disney Meets Darwin)

9 The Biological Clock

An automatic evolution module can also be put into play. Here, the animator can adjust a handful of fitness criteria, and let the population update itself in increments, where the duration of each generation is determined by an adjustable biological clock. Evolution, in this case, is guided by a collection of objective fitness functions. These include such evolutionary pressures as: reward for locomotion, reward for head height, penalty for head/ground collision, penalty for excessive head motion, and penalty for excessive body-flipping. All of these fitness pressures can be adjusted to influence evolution for a variety of motion styles and forms.

At the end of the biological clock's duration, the population is automatically updated, with the more fit individuals contributing the most genetic information to the next generation. A scheme derived from the standard GA operators is used: for each update of the population, pairs of individuals are randomly chosen from the population, with higher chances of being chosen among the more fit individuals, and they mate via crossover - their genotypes are spliced together at random splice-points to give birth to offspring genotypes which inherit "chunks" from each parent. These offspring comprise the next generation. Each offspring may have some small chance of mutation in randomly selected genes, causing some variation in the next generation. The animator can set mutation rate according to how much random "experimentation" is desired for each new generation.

As a layer on top of this automatic process, the animator can contribute to evolution interactively by rewarding certain individuals with fitness values, and by manually updating the population.


10 Results

Back to Beginning of document