Paintbrush and liquid simulation techniques are described. In one or more implementations, input is received to perform brush strokes with a virtual paintbrush on a virtual canvas. For virtual paint on the virtual canvas, lifelike paint qualities are simulated. However, the lifelike paint qualities are simulated solely for the virtual paint that is within a region of the canvas. The lifelike paint qualities are not simulated for virtual paint located outside the region. As part of simulating the interaction between the virtual paint, the virtual paintbrush, and the virtual canvas, various parts of the simulation may be performed by different processing units. For example, bristles of the virtual paintbrush may be simulated utilizing a first processing device such as a central processing unit (CPU). A second processing unit, such as a graphics processing unit (GPU), may be employed to simulate the lifelike effects of the virtual paint.