how i converting the mesh from a 257x257-point mesh to a 129x129-point mesh (or equivalently, a 256x256-cell mesh to a 128x128-cell mesh)

Question

coarsen terrain by a factor of 2. In other words, we will be converting the mesh from a 257x257-point mesh to a 129x129-point mesh (or equivalently, a 256x256-cell mesh to a