.smesh files

Examples are found at here.

A .smesh file represents a piecewise linear complex (PLC) as well as some additional information. The .smesh file format is a simplified version of the .poly format, that each facet only has exactly one polygon, no holes, no segment and point inside. It is less flexible than the .poly file format but is much simpler and useful when the surface mesh is created by other programs.

Part 1 - node list

Part 2 - facet list

Part 3 - hole list

Part 4 - region attributes list

Part 1 lists all the points, and is identical to the format of .node files. <\# of points> may be set to zero to indicate that the points are listed in a separate .node file.

Part 2 lists all the facets. It is different from the facet format of .poly file. Each facet in .smesh file only consists of exactly one polygon. The corner list of each polygon can be distributed over a number of lines. The optional boundary marker of each facet is given at the end of the corner list. If the boundary markers is '1', TetGen will produce an additional boundary marker for each face in .face file (in the last column of each record). You can prevent boundary markers from being written into .face file by using the -B switch.

Boundary markers of facets are tags used mainly to identify which faces of the tetrahedralization are associated with which PLC facet, hence identify which faces occur on a boundary of the tetrahedralization. A common use is to determine where the boundary conditions should be applied to a mesh.

Part 3 lists all holes in the volume. Each holeis specified by identifying a point inside it. After the constrained Delaunay tetrahedrization is formed, TetGen creates holes by removing tetrahedra. Thus exactly is the reason why TetGen requires a closed boundary of the PLCs. In case of non closed PLC facets the whole tetrahedrization will be 'eaten' away. If two tetrahedra abutting a subface are removed, the subface itself is also vanished. Hole points have to be placed inside a region, else the rounding error determines which side of the facet is being transformed into the hole.

Part 4 (optional) lists regional attributes (to be assigned to all tetrahedra in a region) and regional constraints on the maximum tetrahedron volume. TetGen will read this section only if the -A switch is used or the -a switch without a number is invoked. Regional attributes and volume constraints are propagated in the same manner as holes.

If two values are written on a line after the x, y and z coordinate, the former is assumed to be a regional attribute (but will only be applied if the -A switch is selected), and the latter is assumed to be a regional volume constraint (but will only be applied if the -a switch is selected). It is possible to specify just one value after the coordinates. It can serve as both an attribute and an volume constraint, depending on the choice of switches. A negative maximum volume constraint allows to use the -A and the -a switches without imposing a volume constraint in this specific region.

Examples are found at here.

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