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XVOL-ACCUMULATE-UNNORMALIZED-POINT-NORMALS

source files: xvol.[ch]

SYNTAX

(XVOL-ACCUMULATE-UNNORMALIZED-POINT-NORMALS
  :POINT-RELATION <grl:points>
  :FACET-RELATION <grl:facets>
)

DESCRIPTION

CURRENTLY UNIMPLEMENTED.

For triangles, computes cross-product of the first two edges of each facet, and adds them to the :POINT-NORMAL-X/Y/Z value for each vertex in the facet. For quadralaterals, also computes cross-product of the last two edges of each facet, and adds them in.

You will normally want to zero :POINT-NORMAL-X/Y/Z before calling this function (using the pointwise operators) and call XVOL-SET-NORMALS-TO-UNIT-LENGTH afterwards.

Note that the magnitude of the cross-product of the first two edges of a triangle give twice its area, thus the final magnitude of :POINT-NORMAL-X/Y/Z will be twice the area of the facets touching that vertex.

Note: this function really belongs in the thinglist code, not XVOL.


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