Drape polyline to TIn

txrplstxrpls Global Mapper UserPosts: 85Trusted User
Any ideas on how to drape a closed polyline to a TIN and only get 3D vertices where the polyline hits the tin line?


  • My question too... :D  
  • txrplstxrpls Global Mapper User Posts: 85Trusted User
  • Andy WizmaAndy Wizma Global Mapper User Posts: 12Trusted User
    Not sure if this helps exactly:

    Using the digitizer select polyline, then right click "Vertex Editing", then "Edit Feature Vertices" then "Update Elevations from Terrain" 
  • txrplstxrpls Global Mapper User Posts: 85Trusted User
    Not sure if the terrain will be the exact faces of the TIN and the line will drape to those faces and not just the elevations of the vertices. 
  • JeffH@BMGJeffH@BMG Global Mapper Developer Posts: 337Trusted User
    Hi txrpls,

    Using Andy's method, Global Mapper will, for each vertex in the polyline, determine the elevation at that x,y, and it to the z-value of the vertex. Each resultant new vertex will be on the surface of the TIN; however, the resultant 3D polygon will most likely not drape exactly onto the TIN surface, as no intermediate points for the polygon are created.

    If you want a finer approximation of the terrain surface along the polyline, you can resample the line: "Move/Reshape Features" / "Resample/Split Selected Feature(s) at Specified Spacing". You should be able to do this either before or after updating the elevations from the terrain.

    Hope that this helps,

  • Andy WizmaAndy Wizma Global Mapper User Posts: 12Trusted User
    Also, if Jeff's suggestion is not quite what you are after, you can Digitizer right-click on the polyline, then "Analysis / Measurement" then "Path Profile", which will bring up the Path Profile.  Then from there you can at least save out a CSV of the distances / XYZ's which should be exactly as per the underlying TIN (if I remember correctly).  Also the DXF output option will spit out a 3D polyline.
  • txrplstxrpls Global Mapper User Posts: 85Trusted User

    @JeffH@BMG ;

    Thanks for the information, but not exactly what I was looking for as a solution. Let's say one of my vertices from the picked polyline falls in the middle of a face. I would like the elevation of the vertice to be on the plane of the face and new vertices computed where the line crosses the edge of the triangle both entering and exiting the face and not on a spacing. Hope this makes sense. 

  • txrplstxrpls Global Mapper User Posts: 85Trusted User
    @Andy Wizma 
    I'll give that a try. 
  • txrplstxrpls Global Mapper User Posts: 85Trusted User

    After much experimentation, I still do not have a solution. I need my draped line to match the facets of the TIN exactly. I actually need a TIN surface not a GRID surface. How do I get a TIN surface?
  • sphillipssphillips Posts: 210
    edited October 2020
    Did you find a solution in the end? If not, here is a workaround:

    1. Convert the Polyline to an Area Feature
    2. Select the Area Feature
    3. Export the TIN mesh to DWG/DXF using the Area Feature as the Export Bounds (Crop to Selected Area Feature(s)
    4. Import the cropped mesh
    5. Select it
    6. Right-click > Crop/Combine/Split Function > COMBINE
    7. Repeat if any areas remain
    8. Select the combined Area Feature > Advanced Feature Creation Options > Create New Points from Selected Area and Line Features

    Your Area Feature and the Points will be an exact match to the TIN mesh and the vertices are only created where the original polygon intersects the TIN mesh. This workflow does not require you to generate a gridded terrain.


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