Generating polygon meshes that approximate surfaces using root-finding and iteration for mesh vertex positions. In some implementations, a method includes receiving input data that represents a surface that distinguishes an inside and an outside of a volume. A voxel grid that includes the surface is determined, the voxel grid including a plurality of voxels. Particular voxels of the voxel grid are identified, which the surface intersects. A mesh is generated that approximates the surface, the mesh including a plurality of polygons that are defined by vertices in the particular voxels. Generating the mesh includes determining positions of the vertices using a root-finding technique that finds roots of a surface function that describes the surface.