What is simulation? Originally, animated movies were created using traditional hand-drawn animation techniques. Teams of animators would draw all characters and the surroundings frame by frame which would be assembled to compose the final film. But there is only so much a person can draw! Things like water, smoke and fire have extreme amounts of richness and degrees of freedom to their composition and movement, which makes them nearly impossible to animate “by hand” in any reasonable amount of time. That is where technology and physically-based algorithms come in: environmental effects like water, smoke and fire are governed by physical equations, so why not let computers do all the heavy computation to solve those equations. The programs that do this computation are called simulators.