By Polygons – 12D Wiki

Null Triangles – Outside of a Polygon

This option is used to Null (remove) any Triangle whose centroid is outside a selected polygon. Continue down the page to see the Null Triangles Outside Polygon options. To Null Triangles Outside Polygon, Use: Tins => Null => Null After a TIN has been created, it can be edited at any time and one of [...]

Null by Polygons

This option is used to Null (remove) Triangles from a TIN by selecting a single polygon or a model of polygons. Continue down the page to see the Null by Polygon options. To Null Triangles by Polygons, Use: Tins => Null => by Polygons After a TIN has been created, it can be edited at [...]