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Mixed Mesh Generation

The basic idea of producing a quadrilateral is based on generating
consecutively two adjacent triangles that can be merged to form a valid
quadrilateral element. The triangles are created using the triangular
kernel detailly described in
Subsection Surface Triangulation
of Section ** Direct Triangulation of 3D Surfaces**. In order to make the shape
of the generated quadrilateral elements close to a square, which is
considered to be optimal for uniform meshes, the triangular kernel has
to be subjected to minor modifications that can be identified as:

- ideal point creation,
- front processing, and
- convexity check.

Since it is not guaranteed that the boundary of the surface (domain)
is discretized into an even number of edges, an isolated triangle may
remain in the mesh. Moreover, in the presented algorithm, the formation of
a quadrilateral is relaxed whenever it is too difficult or impossible to
generate immediately the second triangle that could be merged with the
first one into a valid quadrilateral (typically in the mesh transition
zones and front closure zones). The resulting mesh is therefore
of mixed nature containing potentially a large percentage of
triangular elements.

** Next:** Quadrilateral Generation
**Up:** Generation of Quad-dominant Meshes
** Previous:** Generation of Quad-dominant Meshes
*Daniel Rypl *

2005-12-07