TIN Cutting to Bounds produces incorrect face normals at boundary

ai3dai3d Global Mapper UserPosts: 25Trusted User
edited October 2013 in Elevation Data
Hi

Im trying to cut up a TIN that i imported from dwg. Im using a grid I imported from dwg as the boundary to slice it up.

When i export the TIN out to dxf faces, the normals on the edge polys are inverted (the wrong way up)Edge Normal problems.jpg

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2013
    Is the orientation of the cropped TINs on the edge being swapped around? For example are the TINs clockwise before, then counter-clockwise after clip? Can you provide a sample with the clip edge? If that is the problem it is likely something we can easily fix.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • ai3dai3d Global Mapper User Posts: 25Trusted User
    edited October 2013
    Ill go check. Im thinking its because the program that the original TIN was made in was 12D. It does seem to like to export TINs with their normals facing downwards. Then when GM interpolates the cut poly it must decide to orient them upward (while the rest of the TINs normal face down).
  • ai3dai3d Global Mapper User Posts: 25Trusted User
    edited October 2013
    Ok, there is no problem with TIN tile rotation. Its just the direction of normals on the newly created edge polys. I upgraded to 15 as I had seen quite a few people who had success with cutting TINs up.

    Thanks
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2013
    Can you provide a source file and cropped with reversed normals that I could check? Global Mapper doesn't calculate any normals, it just stores the coordinates of each corner of the triangle. However I'm thinking if the orientation of those was flipped the calculated normals would be reversed. I just need to verify that is what is happening.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • ai3dai3d Global Mapper User Posts: 25Trusted User
    edited October 2013
    Ok, emailed a chunk of data that exhibits the problem to your email address. The problem become visible when i import the data into 3dsmax.

    Thanks Mike
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited October 2013
    I actually made an update to make sure the cropped TINs have the same direction as the originals, so if you go to Global Mapper Downloads and install the latest you can see if that fixes the problem.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • ai3dai3d Global Mapper User Posts: 25Trusted User
    edited October 2013
    Thanks Mike, you are a champ. That worked a treat. Now ive been able to slice and move a TIN and export. It would be good to see some extra options on export to dxf, eg option not to export splines. Also, how does GM handle coincident points, does it cull them?

    Cheers

    Steve
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