Problem

 I have a DXF file with a large number of triangles. I’m attempting to create Terrain using the Terrain > From Elements tool.

 It is possible to do, but the process takes too long. Sometimes hours.

 

Solution

 The process above takes a lot of processing due to using the element selection tool.

 When you are dealing with a large number of elements to create the Terrain, it is advised to use the Graphical Filter tool.

 That bypassed the element selection process and creates the Terrain directly.

Example:

1. Created a new 3D dgn
2. Reference the DXF file
3. Created a new graphical filter for Level 0 (assuming all triangles are in Level 0)
4. Then used, that filter to generate the Terrain.

 

Refer to the wiki below on how to create a terrain from a graphical filter

 Video: Create Terrain From Graphical Filter