I have a map of heights of a city in format raster ascii, use terrainblock to create the map in 3D, but the walls prove to be sloping, since there are in use a number of equal vertices to the matrix of the file ascii, who method to do that the walls not sloping show?.
Terrainblock is generally used for landscape, like hills and plains.
You put models of your walls and buildings on top of this.
If you want something based on your image map, you could maybe create a grid of boxes of different heights on your landscape…