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Unity terrain made of 4 * 4 polygons has 5 * 5 vertices.
Heightmap pixel controls each of the vertices. This way heightmap resolution is 5 * 5 as well (i.e. 4+1)
When applying a control map, Unity is making half-pixel offset from each size (possibly to align it the same way )
Control map resolution matches heightmap resolution
Note each control map pixel is located exactly on terrain vertex position.
Still consistent if height resolution is 65 x 65, and control map resolution is 33 x 33