number of columns of grid vertices
number of rows of grid vertices
column spacing in world units
row spacing in world units
(c, r) => boolean, whether the grid vertex at column c,
row r lies inside the footprint
world X of column 0 (default 0)
world Z of row 0 (default 0)
Build a flat plane at
y = 0covering the cells of a regular grid for which apresentpredicate holds at all four corners, so the plane follows the outline of an arbitrary (possibly holed) footprint rather than a plain rectangle. Unused grid vertices are dropped (compacted) so the result can be cheaply subdivided afterwards. UVs span[0, 1]across the full grid extent.