Physically Based Fluid simulations like liquids, fire, and smoke are difficult to control creatively because they are governed by complex equations (PDEs). That is, the fluid’s state depends on all previous states, so making changes to a specific frame requires altering initial conditions, which is extremely challenging. This results in artists having to go through tedious and time consuming iterations.
A method that allows artists to add creative control at any point in time of the simulation without recomputing previous steps. This is done through intuitive tools like sketches and brushes, making it easier and faster to achieve the desired visual effects.