Can Point Cloud data be clipped and converted into a DGN file? / Best method for creating a surface

Question

Hi, 
 I have a large point cloud area, but I only require a small section. The file is currently too large to work with. 
 Can I crop the desired area and create either a new *pod or DGN file? 
 Also, what is the best method of creating a surface/mesh? 
 The area is a railway line with an over bridge & general railway infrastructure e.g. gantries, signals, etc. 
 
 Thanks 
 
 Matt

George A. Martin · Accepted Answer

Separate the Point Cloud till you have the area of points you want. Export/Save the resulting .pod as a ASCII file .XYZ or ,txt. 
You should be able to use the XYZ Text tool (Tools > Tool Boxes > XYZ Text) to import those points and use those points to generate a Mesh using the Mesh from Points tool.

Mathieu St-pierre · Answer

Hi Matt, 
 
Bentley Descartes has a tool (i.e. : Tile Export) to create different smaller POD regions for a big POD. 
 
Also with Bentley Descartes you can create a Scalable Terrain Model directly from the original POD file. From that Scalable Terrain Model you can then generate Terrain Model elements for the ROI to perform various analysis with Bentley civil application (e.g. : Open Road). 
 
Thanks, 
 
Mathieu

George A. Martin · Answer

Hi Lorys 
 In a MicroStation 3D Model, go to the point Cloud dialog (File > Point Cloud). 
 Attach your Point Cloud (which will automatically convert it to a .pod) 
 Under "Edit" in the Point Cloud dialog, Clip the point Cloud to show what you want. 
 Go to File > Export (set the Export to Format = ASCII Files (*.xyz), Region Filter = Clip, set the Density to the % of points you want from the Cloud & OK 
 Go to the XYZ Text tool in M-Sta. (Tools > Tool Boxes > XYZ Text) 
 Go to the "Import Coordinates" tool in the Tool Box 
 Browse to the exported points file you created ?.xyz 
 Set the Import options to Point Element Order X,Y,Z and set the view > Process 
 It should bring the points in so you can use the "Mesh From Points" tool. 
 Hope I didn't miss anything. I have Descartes too, but there are additional Convert options to go to xyz.txt in M-Sta. alone. 
 You helped me in past a lot. Glad I can return the favor!