1. A method for smoothing a three-dimensional (3D) mesh, the method comprising: identifying a set of vertices within an area of the 3D mesh that is operated on by a volume-preserving mesh smoothing brush that is configured to smooth the 3D mesh; for each vertex in the set of vertices, computing a modified position based on the operation of the volume-preserving mesh smoothing brush, and computing a length of a Laplacian vector corresponding to the modified position computed for the vertex; computing, for the set of vertices, an average length based on the lengths of the Laplacian vectors computed for the vertices in the set of vertices; estimating a change in volume of the 3D mesh based on the modified positions computed for the vertices in the set of vertices; computing, for each vertex in the set of vertices, an updated position of the vertex based on the modified position computed for the vertex, the average length computed for the set of vertices, and the estimated change in volume of the 3D mesh; and inflating the 3D mesh based on the updated positions of the vertices, wherein the volume of the 3D mesh after being inflated is substantially the same as the volume of the 3D mesh before being operated on by the volume-preserving mesh smoothing brush.