The quick answer is you can't.
For a 32x32 terrain you actually need a 33x33 heightmap, however blitz doesn't support this. The usual solution is to make everything an island (0 heights round the edges) so it wraps, or indeed make sure the terrain wraps perfectly itself.
For a 32x32 terrain you actually need a 33x33 heightmap, however blitz doesn't support this. The usual solution is to make everything an island (0 heights round the edges) so it wraps, or indeed make sure the terrain wraps perfectly itself.