5.2.1 Triangle

The most basic one among these is the triangle object, with syntax:

TRIANGLE:
  triangle { CORNER1, CORNER2, CORNER3 [OBJECT_MODIFIERS] }

See also:

• [pov:6.5.2.6]Triangle and Smooth Triangle

This describes a triangle with the three 3d-vectors CORNER1 ($=C_1$), CORNER2 ($=C_2$), and CORNER3 ($=C_3$) as vertices, i.e.

$$\{\sum_{i=1}^3 t_i\,C_i:t_1,T_2,T_3\geq 0,\sum_{i=1}^3 t_i=1\}.$$