Polyhedron Loop Element (POLOOP)

Primitive Element

Description:

The POLOOP represents a planar profile which defines all or part of the shape of a Polyhedron Face (POLFAC). It is defined by a set of edges linking adjacent Point (POIN) elements, the latter being identified by references held in a Loop Points element (LOOPTS) owned by the POLOOP.

The order of the vertices (that is whether they are sequenced clockwise or anticlockwise) is significant. The order for a loop representing a positive polyhedron face is the opposite to that representing a negative polyhedron face. The LMIRR attribute determines whether the face points are read from start to end of the list, or in reverse. Reversing the order changes the loop from a positive outer boundary to a negative hole boundary, or vice versa. By default, points listed anticlockwise correspond to a positive boundary.

Attributes:

Legal Owners:

Polyhedron Face Element (POLFACE)

Legal Members:

Loop Points Element (LOOPTS)

The directions clockwise and anticlockwise refer to the sense when looking from outside of the face into the polyhedron.