Simplex

Simplex[{p1, ..., pk}] represents the simplex spanned by points pi.

Examples

Create a 2D simplex (triangle):

Graphics[Simplex[{{0, 0}, {1, 0}, {0.5, 1}}]]

Create a 3D simplex (tetrahedron):

Graphics3D[Simplex[{{0, 0, 0}, {1, 0, 0}, {0.5, 1, 0}, {0.5, 0.5, 1}}]]

Please visit the official Wolfram Language Reference for more details.