WMS:TIN Options

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The TIN Options dialog controls setting for several of the TIN creation and editing functions.

TIN Options dialog

Vertex Options

There are two different modes for creating vertices, digitizing and non-digitizing modes. In digitizing mode all of the options for triangulation of new points, confirmation of z values etc. are disabled and the z values of newly created vertices are determined by the z value entered in the z edit field of the edit window. Newly created vertices are not triangulated into a TIN so triangulation of vertices should be done once digitizing vertices is completed. See creating a TIN from a scanned image for more information on how digitizing mode can be used to create a TIN from a contour map.

In non-digitizing mode there are several options that control what happens to vertices and triangles of a TIN when new vertices are created:

  • If the Retriangulate after deleting is checked, the region surrounding the vertex will be retriangulated as each vertex is deleted. Otherwise, the triangles adjacent to the vertex are simply deleted.
  • If the check box entitled Adjust boundary to include exterior vertices is selected, the boundary of the TIN will be changed so that the new vertex becomes part of the TIN if a new point is added outside the active TIN. If the new vertex is in the interior of the active TIN, the vertex will be automatically incorporated into the TIN.
  • If the check box entitled Confirm z values item is selected, WMS will prompt for a z value every time a new vertex is created.
  • If the Interpolate for default z on interior item is checked and a new vertex is entered in the interior of a TIN, the program will linearly interpolate a default z-value from the plane equation defined by the triangle containing the point.
  • The Default z value edit box displays the z value that will be assigned all subsequent new vertices created with the Create Vertex tool if the Confirm z values check box is not selected.
  • If the Extrapolate for default z on exterior item is checked and a new vertex is entered outside the TIN boundary, the program will extrapolate a default z-value by using a gradient based inverse distance weighted interpolation.
  • The Duplicate vertex tolerance edit box shows the tolerance used for such TIN operations as removing duplicate vertices, insertion of breaklines, and dividing drainage boundaries. Normally is is not necessary to change this value, but occasionally it becomes the only way to work around sticky numerical problems.
  • The maximum filter angle is used when thinning dense vertex lists for more reasonable management. This is particularly useful when processing TINs generated from LIDAR technology.

Triangulation Optimization

There are two different ways of generating an initial triangulation of the xyz vertices for a TIN.

  • Angle Optimization prioritizes the creation of triangles with as near equal angles as possible.
  • Area Optimization prioritizes the creation of triangles with as near equal areas as possible.

Triangle Options

The triangle options are used when searching for thin boundary triangles to eliminate after performing an automated triangulation.

Breakline Options

When enforcing breaklines with feature arcs, elevations can be linearly interpolated from the TIN, or derived from the z-values of the feature vertices (of course it is important that z-values are defined for the vertices if this option is selected).

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