Abstract : We present a simple and physically inspired method to animate realistically looking fire directly in 2D instead of along a 3D simulation. This naturally reduces the complexity of the animation from O(n3) to O(n2). The fire is represented as a 2D scalar density field located on a plane facing the camera, and is advected under a 2.5D velocity field. In our method, the apparent motion of the fire on the viewing axis is mimicked by introducing vibrations in the velocity field. We model these rapid vibrations as pressure waves found in compressible fluids and therefore consider the full Navier-Stokes equations. The equations can be solved in a single pass and our method entirely runs on the GPU. A natural extension is to make use of this method directly in screen space: instead of filtering down the fire's simulation grid in world space, we rasterize the fire's source, and perform the simulation on a coarser grid directly in screen space. The results are constantly renewed 3D-looking fires computed solely in 2D.