Add CHANGELOG up to TetGen v1.4.3
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Juergen Fuhrmann
Juergen Fuhrmann
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CHANGELOG.md
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CHANGELOG.md
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# TetGen: Release Notes
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## Version 1.4.3 (September 6, 2009)
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- A new implementation of the Bowyer-Watson algorithm for Delaunay
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tetrahedralization. It is generally faster than the incrmental flip
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algorithm. From my tests, the flip algorithm usually constructs
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about twice (or more) as many intermediate tetrahedra as B-W
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algorithm. Now B-W algorithm is the default algorithm for Delaunay
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tetrahedralization.
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- A new implementaton of the constrained Delaunay tetrahedralization
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algorithm (the -p option).
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- A new implementation of the Steiner point removal algorithm (the -Y
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option).
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- Improved the implementation of the constrained Delaunay refinement
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algorithm (the -q option).
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- Add the minimum dihedral angle of tetrahedra as the tetrahedral
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shape quality parameter (set after -qq option). The minimum dihedral
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angle is made the major mesh quality measure now. Default it is 5
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degree. One can increase it as larger as 18 degree. The radius-edge
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ratio (set after -q option) is still in use.\
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For an example, the string \'-q1.4q10\' sets both a radius-edge
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ratio (\<= 1.4) and a minimum dihedral angle (\>= 10 degree) as the
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tetrahedral shape quality measure.
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- Support the read and write of the legacy VTK file format which can
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be visualized by Paraview (see .vtk file format and -K option).
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## Version 1.4.2 (April 16, 2007)
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- Improved the constrained Delaunay mesh refinement algorithm. Slivers
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(very flat tetrahedra) are removed during the mesh refinement. For
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geometries having no input angle and dihedral angle smaller than 60
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degrees, the boundary conforming Delaunay mesh property is
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guaranteed, hence the dual Voronoi diagram has no vertex lies
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outside the domain boundary - a desired property for finite volume
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partition.
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- Mesh coarsening (deleting mesh points) is now possible. Two ways are
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implemented for doing mesh coarsening: (1) The user can specify the
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points wanted to be removed by using the \"pointmarker\" list (i.e.,
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the last column in .node file), a \'0\' means \"remove this point\",
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otherwise \"keep it\"; or (2) The user can supply a mesh sizing
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function, let TetGen choose the point to remove, i.e., TetGen will
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remove a point if the mesh size at the point is too dense.
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The new command line option for mesh coarsening is \'-R\'. It can be
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used either with \'-p\' (to coarse a CDT) or \'-r\' (to coarse a
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previously generated mesh). You can also use \'-R\' and \'-q\'
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together. TetGen will first perform mesh coarsening then do mesh
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refinement, hence the process must terminate and the mesh quality is
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improved.
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- Implemented new mesh optimization and mesh smoothing functions which
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can be optionally performed to remove slivers and further improve
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mesh quality. High order edge flip operations (combination of
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several basic flips) (as suggested by Barry Joe \[Joe, 1995\]) are
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implemented. These operations help to remove the majority of
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slivers. The remaining slivers are then tried by mesh smoothing
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operations, which includes vertex moving and new vertex insertion.
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- Improved the mesh boundary preserving (the \'-Y\' option) function.
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Most of the relocated interior points can be completely suppressed,
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remaining points are smoothed.
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- New output of Voronoi diagrams. The Voronoi diagram is the geometric
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dual of the Delaunay triangulation. By using the \'-v\' option, the
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Voronoi diagram will be saved in files: .v.node, .v.edge, .v.face,
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and .v.cell.
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- Many bugs are fixed including the \'-o2\' option.
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## Version 1.4.1 (July 28, 2006)
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- An adaptive mesh refinement algorithm has been implemented (for the
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\'-q\' option). This algorithm extends Shewchuk\'s basic Delaunay
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refinement algorithm in two ways: (1) no restriction on the input
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angle; (2) refines the mesh according to a sizing function which may
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be automatcially derived from input data or provided by user through
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a background mesh. A paper, \"On Refinement of Constrained Delaunay
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Tetrahedralizations\", describes the algorithm will appear in the
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proceeding of 15th international meshing roundtable, Birmingham AL,
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September 2006.
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- The \'-Y\' option (preserve the input boundary) has been improved.
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Generally, more than 95% additional points can be completely
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removed, the remaining points are relocated into the volume.
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- Many bugs are fixed.
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## Version 1.4.0 (January 14, 2006)
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- Respect of the input boundary (the \'-Y\' switch). It is possible
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now to preserve the input surface mesh unchanged in the result
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tetrahedral mesh. A Steiner point removal algorithm based on
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Delaunay tetrahedralization kernel and constrained flips is
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implemented.
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- Shewchuk\'s Delaunay refinement algorithm has been improved. A new
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type of Steiner point called \"off-center\" (suggested in paper
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Alper Üngör, \"Quality Triangulation Made Smaller\", EWCG 2005) is
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used. This change reduces the number of refinement points (up to
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20%) and results in smaller meshes. Consequently, the mesh speed is
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improved too.
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- The constrained Delaunay tetrahedralization algorithm is improved. A
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simple symbolic perturbation is used to remove the spherical
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degeneracies of the point set which reduces the number of break
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points (thanks to Jonathan Shewchuk).
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- It is possible to let TetGen automatically assign the region
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attributes to tetrahedra. When the \'-AA\' switch is used, in the
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output mesh, every tetrahedron gets a non-zero attribute. Tetrahedra
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in the same region have the same attribute.
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- The \'-z\' switch has been activated. The ouput nodes can be indexed
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from zero.
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- Many bugs are fixed.
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- Many typos in the user\'s manual are corrected (thanks to David
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Day).
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## Version 1.3.4 (June 17, 2005)
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- A new constrained Delaunay tetrahedralization algorithm has been
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completely implemented. Now the CDT construction is rather fast and
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stable. A paper, \"Meshing Piecewise Linear Complexes by Constrained
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Delaunay Tetrahedralizations\", describes the algorithm has
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submitted to the 14th international meshing roundtable held in
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Sandiego, September. Colleagues who have the interest to read it are
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very welcome to contact me.
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- In the -q switch. A new strategy for edge protecting has been used
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in the Delaunay mesh refinement which saves a quite number of
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additional points. It is a slighly modified version of our edge
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protecting algorithm (also presented in the above paper). The
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quality mesh step is more stable than old ones.
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- In the -q switch. A sliver removal step is added after the Delaunay
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refinement. It removes most of the survived slivers by flip
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operations and inserting points.
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- In the -q switch. More mesh refinement options are available.
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Besides the maximum volume constraint on tetrahedra, users now can
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set maximum area constraints on facets, maximum edge length
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constraint on segments.
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