A method and system provide the ability to design a (land) surface. A triangular surface mesh representative of an existing surface is obtained. The mesh includes triangles that are connected by vertices and edges. Design constraint sets are determined based design constraints. The design constraints include a maximum slope constraint for a first triangle of the two or more triangles in the triangular surface mesh. The maximum slope constraint is a maximum angle between a normal vector of the first triangle and a reference vector. Heights of the vertices of the first triangle are projected onto the design constraint sets such that the normal vector satisfies all of the design constraints. The projecting includes modifying the heights by a minimum Euclidian distance. A design of the surface represented by the triangular surface mesh is generated based on the projecting.