OOF2: The Manual
Refine (Refine) — Subdivide elements.
- Target elements to be refined. Type: An object of the
- Exclude certain elements. Type: An object of the
- Preferred way of subdividing a side. Type: An object of the
- alpha controls the relative importance of element shape and homogeneity. alpha=0 emphasizes shape and ignores homogeneity. alpha=1 emphasizes homogeneity and ignores shape. Type: A real number in the range [0, 1].
Refine is a SkeletonModifier that chops its target
elements and their neighbors into smaller pieces. This adds more
degrees of freedom to the
Skeleton, which allows it to adapt better
Microstructure. Refinement by itself is rarely sufficient to
create an acceptable
Skeleton -- it must be combined with other
move nodes, such as SnapNodes or
The steps involved in refining a
Find the element edges (
Segments) that need to be refined. These are specified by the
targetsparameter, whose value is a RefinementTarget object. Different kinds of RefinementTarget objects pick segments in different ways, for example, by choosing all edges of heterogeneous elements or the long edges of skinny elements. See RefinementTarget for the details.
criterionparameter is used to exclude certain elements and segments from the marking process. Setting it to Unconditional means that all elements and segments are possible candidates for refinement.
Figure "Refining a Skeleton" (a) shows a
Skeletonthat needs to have its heterogeneous elements refined. Setting
CheckHomogeneity(threshold=1)marks the edges of all elements whose homogeneity is less than 100%, as shown in Figure "Refining a Skeleton" (b).
Sometimes the way in which the elements will be subdivided (determined by the
degreeparameter) requires extra segments to be marked. In these cases a second pass is made through the
Skeleton, marking additional segments.
After the segments are marked, each element is replaced by a suitable collection of smaller elements, such that each marked segment of the old
Skeletonturns into a set number of segments of the new
Skeleton. Exactly how this is done depends on the setting of the
degreeparameter, which determines both how many new edges replace each old edge, and how the new elements are arranged within the old element. (For details, see the descriptions of RefinementDegree and RuleSet.) The rules sometimes allow more than one way of subdividing an element. In those cases, the total effective energy of the new elements is computed, and the configuration with the lowest energy is used. The parameter
alphadetermines the relative contributions of shape and homogeneity to the effective energy, as discussed in Section 220.127.116.11.
One should not abuse Refinement to the point where elements
become too small. Figure 6.92 shows a part
Instead of abusing refinement, it is better to employ other
modification strategies. Figure 6.93
shows the same portion of the
As seen, refining too much does not necessarily yield an optimal
result. One can, however, prevent this over-refinement by
adjusting the refinement