Particle Baking

Besides creating smoke, fire, dust, etc; particles can be used to create some very interesting results by recording their positional information. By baking out the particles' positions from frame to frame into seperate text files, motion curves can be extrapolated and used for effects such as fireworks, energy beams, and even vegetation growth. The images and movies below depict playblasts of the particles in motion, the curves generated from their paths, and an effect generated using Renderman shaders.

The video to the left demonstrates how particles can be used to generate alternative effects. Particle motion is used to derive the paths the vines grow throughout the city.

This interface allows me to set the beginning and end frames for the particle baking. I can also determine where my data files will be stored and the name of the MEL script that will be created. Most importantly, I can specify the number of curve points to be skipped when converting the data points into a Maya curve. Most of the time, creating a curve control point for every frame is unnecessary and computationally expensive, especially when numerous particles are simulated.

The playblast to the left shows how the particles follow a goal object that moves through the scene. The particles dynamically collide with the buildings and have a turbulence field applied so that the vines will grow with some randomness.

Once the particle position information has been baked out, I can use the data to create curves. Extruding these curves gives me the geometry of the vines and then a custom transparency shader can be applied.