Splinter Tetrahedron

A splinter tetrahedron is a long, thin tetrahedron with two separated close pairs of vertices (Cheng et al. 2012, p. 25; Hannukainen et al. 2017, p. 3).

In the degenerate limit, each pair coalesces at a different endpoint, so the shape approaches a line segment. A spindle tetrahedron instead has four distinct limiting positions. These are qualitative shape names used in tetrahedral mesh classification.