There is two methods for controlling the area over which triangles are created, Maximum Side Length and TIN Boundary Feature Property.
Maximum Side Length Control
A common problem which occurs when creating a DTM is that large triangles often formed across void areas. To prevent this from occurring the Maximum Side Length parameter can be used to restrict the size of the triangles created. To estimate the Maximum Side Length enable horizontal and vertical grid line display. The following figures illustrate the use of side length control.
Figure 1. Erroneous Triangles Extending Across a Void Area
Figure 2. Triangles Generated with Maximum Side Length Control
TIN Boundary Feature Property
When triangles are created, features with the TIN Boundary property turned on are used to limit the extent of the triangulation. All triangles with their center point inside the a TIN Boundary polygon will be retained. If the TIN Boundary feature has the "Negative Area" property set then its area will excluded.
