OOF2: The Manual

Details

Description

FixIllegal is a SkeletonModifier that fixes illegal Skeleton Elements.

Excluding paranormal alien interventions, illegal elements are only generated by moving Nodes manually with the Move Nodes toolbox. Illegal elements are BAD, so they should be removed immediately.

FixIllegal works by finding the trouble spots in each Element, namely the corners which have non-positive interior angles. The Nodes at those corners are moved to the average position of their neighboring Nodes. The move is accepted or rejected solely by whether or not it reduces the number of illegal Elements in the vicinity.

Figure 6.80 shows a Skeleton that gives a pretty good representation of the underlying Microstructure. Figure 6.81 shows the Skeleton after a Node has been moved to create two illegal Elements (shown in red). The node motion is indicated by the arrow in Figure 6.80. Figure 6.82 shows the Skeleton after FixIllegal has been applied. Notice that although there are no illegal Elements, the Skeleton is no longer such a good representation of the Microstructure. This is because FixIllegal is a brutal technique: it pays no attention to Element homogeneity or shape energy.

Figure 6.80. A Legal Skeleton

Figure 6.81. An Illegal Skeleton

Figure 6.82. A Rehabilitated Skeleton

On one pass through the Skeleton, FixIllegal attempts to move each troublesome Node once, choosing the Nodes in a random order. It may not be successful on the first pass, so it repeats the process until there are no more illegal Elements. If it fails to remove all the illegal Elements after a fixed number of iterations,^[24] it will quit trying and notify the user.