Common Operator Info
The input position vectors are scanned for invalid numbers, potentially the result of math operations where there is no solution. Such erroneous conditions can be indicated with a special value of "not a number" which has the unusual property that it is not equal to itself (or anything else).
An optional Replacement Surface should be like the Input Surface in topology, but known to have valid points, perhaps from a reference pose. In practice, while it makes sense to use the same topology, only point positions are actually queried.
If a Replacement Surface is provided, a replacement value is queried from that surface at the same point index. If it is not provided or it does not have enough points, an origin value of all zeros is used for a replacement.
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