OOF2: The Manual

Details

Description

MergeTriangles merges two triangular Elements into one quadrilateral Element.

MergeTriangles is more or less the opposite of SplitQuads, which splits a quadrilateral into two triangles. Given the nature of the process (merging elements), it is easy to see that it focuses mostly on reducing elements' shape energy rather than increasing elements' homogeneity. It also reduces the overall degrees of freedom in the resulting Mesh, thereby decreasing the solution time (and accuracy), if the Mesh is going to be built from high-order elements. For Meshes made of linear elements (4-noded quads or 3-noded triangles) Merging Triangles does not reduce the number of degrees of freedom.

The targets parameter specifies which Elements in the Skeleton to examine. Taking the Elements in random order, OOF2 tries to merge each Element with each of its neighbor elements in turn (whether or not they're in the target list), if the neighbor is a triangle and has the same dominant pixel type as the target Element. The criterion parameter specifies which, if any, of the possible merges to accept.

Figure 6.85 shows a few highlighted triangle pairs to be merged. The resulting Skeleton is shown in Figure 6.86.

Figure 6.85. Triangles To Be Merged

To-be-merged triangle pairs are highlighted.

Figure 6.86. After Merge

Triangle pairs have been merged to form quadrilaterals.