This data item defines a triangle in space.
Other data items can check if nodes are located on this geometry.
The coordinates of the corner points
are *x_0 y_0 z_0* etc.. In 2D the coordinates should not be
specified. All **node** within a distance *tolerance* are considered
to be part of the triangle (this gives a wedge with thickness
).

tochnog 2001-09-02