source files: xvol.[ch]
(XVOL-COMPUTE-UNNORMALIZED-POINT-NORMALS :THING <thing> )
Compute a normal for each vertex by averaging the normals of its adjacent facets. The results are stored in the :POINT-NORMAL-X/Y/Z value for the point. This function relies on having :FACET-NORMAL-X/Y/Z arrays, which can be computing using XVOL-COMPUTE-UNNORMALIZED-POINT-NORMALS.
Current implementation works only for things of triangles or quadrilaterals.
You will normally want to call XVOL-SET-POINT-NORMALS-TO-UNIT-LENGTH afterwards.
Note: this function really belongs in the thinglist code, not XVOL.