OOF2: The Manual
Name
Merge Triangles (MergeTriangles) — Merge neighboring homogeneous triangles to form quadrilaterals.
Synopsis
MergeTriangles
(targets
,criterion
)
Details
-
Base class:
SkeletonModifier
-
Parameters:
targets
- Which elements to modify. Type: An object of the
SkelModTargets
class. criterion
- Acceptance criterion. Type: An object of the
SkelModCriterion
class.
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.