OOF2: The Manual

Details

Description

MergeTriangles merges two triangular Elements into one quadrilateral Element. It is more or less the opposite of SplitQuads, which splits a quadrilateral into two triangles.

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.

If a Mesh is going to be built from high-order elements, merging the triangles in its Skeleton reduces the overall degrees of freedom in the Mesh, thereby decreasing the solution time (and possibly accuracy). For Meshes made of linear elements (4-noded quads or 3-noded triangles) merging triangles does not reduce the number of degrees of freedom.

Figure 6.89(a) shows a few highlighted triangle pairs to be merged. The resulting Skeleton is shown in Figure 6.89(b).

Figure 6.89. Merging Triangles

(a) The Elements with green edges are triangles that can be merged.

(b) The result of running

          OOF.Skeleton.Modify(
             skeleton='swoops.png:skeleton',
             modifier=MergeTriangles(targets=AllElements(),criterion=AverageEnergy(alpha=0.5))) 

on the Skeleton in (a). (The green edges indicate the affected Elements for illustrative purposes only. Selected Segments were not actually necessary to run this command.)

See Also