US Patent 7557807 Visual simulation of weathering by y-ton tracing

An exemplary computer-implementable method includes providing a computer-generated object wherein the object has characteristics, emitting a computer-generated particle, determining if the particle interacts with the object and, if the particle interacts with the object, altering one or more of the characteristic of the object wherein the altering simulates weathering or aging of the object. Various other exemplary techniques are also disclosed.