Blender GIS producing blocky contours in low relief areas

Hi All,

I’m experimenting with hill shading using Blender GIS, as discussed in this tutorial:

I’m following the process outlined here but am not completely happy wit my results. A problem that I run into consistently is the appearance of blocky ‘contour lines’ that show up in low relief areas of my projection. I don’t see this in the examples rendered by others online. Any idea what causes this and how to avoid it?

Screenshot below. Gridded to 10 feet, subsurf set to 11.


Zoom of contour-like artifacts: