MX Triangulation (v8i)There are two methods for generating surface triangulations. The most common method involves the use of an Input File. The other method is Interactive. Both are described on this page.
Input File Triangle Generation
The following sample input file is intended for generating a triangulation of a surveyed detail model:
COMPILED BY username, date
019,L B ,4=1
019, B ,4=-1
If an output file already exists, MX will not automatically overwrite or replace it. Therefore the beginning of this file contains commands to clear the old output file. Major option Output creates a new output file and begins recording.
If a triangle model exists, then it is necessary to avoid appending model detail with itself. Therefore Delete the model detail prior to new input (It never hurts to delete a model that is not there). Since a potentially large model has just been deleted, take this opportunity to Compress the model file. Then Create the triangle model to prepare for the following input.
After the Triangle major option records are the 019 masking minor options. See String Masking for more details about masking. This sample file contains most of the recommended strings to mask. This list may vary from project to project.
The 960 minor option generates the initial triangulation. The 961 minor option trims the triangulation to eliminate triangles that span outside valid string data. Refer to the MX Command Language Reference manual (or the Moss Quick Reference Guide) for details about major and minor options.
Near the end of the file but before major option Finish, is major option Output. With no file specification, this option will close the output file initiated at the beginning of this file.
Refer to MX Input Files for a greater explanation of input files.
Triangulation models created from input files are not assigned style and feature sets. The appropriate model defaults for triangulation models is MfW Triangulation.pts/fns. Refer to Style Sets for directions on assigning model defaults.
Interactive Triangle Generation
From the Analysis menu, select Triangle >> Triangulation from a String Model...
The Triangulation from a string Model panel has three tabs grouping the required data.
On the Model Details tab, supply the string Model to Triangulate. The recommended mask table for surveyed detail models is the GroundTriangle.msk file. Similar to the sample input file, this file contains most of the recommended strings to mask. This list may vary from project to project. The recommended mask table for design models is the Design Tria.msk file. Once a mask file has been selected, the mask control box should say Apply Current Masking. Refer to String Masking for a greater explanation of masking.
Next, supply the Model to Store Triangulation and the Triangulation String Name. Refer to Model Names for MX for our standard model naming convention. Ensure that the model default for the triangulation model is MfW Triangulation.pts/fns. Refer to Style Sets for directions on assigning model defaults.
At the bottom of the Model Details tab is a Display Triangles check box, leave this box checked to display the generated triangles.
At the top of the Boundary Details tab is an Analysis within a Boundary check box. Check this box if triangulation is to be limited to a bounded area. Supply the Boundary Model and Boundary String as necessary.
At the top of the Trimming Details tab is a Trim check box. Check this box to trim the triangulation.
There are three trimming options to choose from
- Trimming Method A (Shrink) To trim all triangles at the edge of the triangulation whose subtended internal angle is greater than 90 degrees and the opposite edge is not a string link. The most common trimming method. Recommended for detail surveys.
- Trimming Method B (All) To trim all triangles at the edge of the triangulation whose subtended internal angle is greater than 90 degrees and all three triangle edges are not string links. Rarely effective.
- Trim to a Boundary To trim all triangles at the edge of the triangulation whose centroid lies outside a specified boundary. This option used when Trimming Method A (Shrink) proves to be inadequate.
Select OK to generate the triangulation.
The Surface Analysis panel is the entry to 10 surface analysis options: