Triangulation.

This tool allows you to create a Digital Terrain Model (DTM) from a set of points and/or breaklines. The result is a triangulation containing 3D Faces representing the surface of the terrain. Furthermore, FlashMNT can create a triangulation containing holes and/or limit the triangulation zone on a predefined boundary .

For the triangulation to be correct and succeed, it is essential to make sure of the integrity of your initial data by using the tools: Data Verification and Optimization of 3D Polylines.

Select the Points : Check this option if you are creating a DTM from points.

Choose the entities to use as points :indicate which entity types represent the points. In general, they are Autocad POINT entities, but you can also use BLOCKS (in general a block is composed of a point and the attributes: Number and Altitude). In this case, the block insertion point will be used as coordinates.

• Points : Check this option to use POINT entities.
• Blocks : Check this option to use BLOCK entities

Select the breaklines : Check this option if you are creating a DTM from polylines.

Choose the entities to use as breaklines

• 3D Polylines : Check this option to use 3D Polylines.
• 2D Polylines : Check this option to use 2D Polylines.
• Lines : Check this option to use Lines.

Boundary and Holes

• Select a boundary : Check this option if you want the triangulation to be limited to a zone contained in a boundary. It will then have to be a closed polyline enclosing the project. FlashMNT will prompt you to select the boundary when required. (Use this tool to search the contour of a set of points).
• Select Holes : Check this option if you want to tell FlashMNT about the zones located inside the DTM that should not be triangulated. These zones should be composed of closed polylines.

Create the Triangles : Check this box to create the triangles.

• Layer : Enter the name of the layer in which the triangles will be created, or click on to choose from a list.
• Erase the Layer content : Check this option for the contents of the layer -in which the triangles will be created- to be erased a the launch of the command.

Display the report after triangulation : Check this option to display the triangulation report a the end of the processing.

Adjust the parameters of the dialog box, then click on "OK". FlashMNT then displays on the command line :

>> Select the objects :

Select the desired objects (points and/or breaklines) then validate. If you have checked "Select a boundary, "FlashMNT then displays on the command line :

>> Select the boundary :

Click a closed polyline or press <ENTER> to skip.

If you have checked "Select Holes" option, FlashMNT then displays on the command line :

>> Holes Selection
>> Click a point within a hole or <ENTER> to finish :

Click then successively inside each hole, then <ENTER> to finish and launch the triangulation.

Remarks : After creating a DTM, it is advised to verify it by using the command DTM Control.