Examples of Bad Tetrahedral Elements

Five kinds of tetrahedra with small Hausdorff distance to a line segment.

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Spear requires vrml viewer.

Spindle requires vrml viewer.

Spike requires vrml viewer.

Splinter requires vrml viewer.

Four kinds of tetrahedra with small Hausdorff distance to a piece of a plane.

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Spade requires vrml viewer.

Cap requires vrml viewer.

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The first eight kinds of bad tetrahedra has either large circumradius r or small shortest edge length l. Sliver can have either small or large r/l but always small v/l^3 where v is its volume.
The regular tetrahedron minimizes r/l at about 0.612.