geometry_triangle index x_0 y_0 z_0 x_1 y_1 z_1 x_2 y_2 z_2 tolerance

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 $z$ 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 $2 \ast tolerance$).