close/fill holes in mesh (TIN)

AlexW

Dear community,

i searched the knowledgebase and the forum, but even though it's a basic process i didn't find a an answer. So maybe you could help.

After creating a 3D model (mesh) from a subsampled point cloud there might be spikes and vertical fragments left, that i want to cut out manually. Afterwards i want to re-mesh the resulting hole.

The "Close gaps between adjecent features" tool sounds like a good choice, but gives "overmeshed" results - depending on the entered distance.

Can you recommend better settings, or another tool to use in GM?

Thanks a lot

Alex

RonTheSurveyor

What about manually adding some lines by snapping to the triangle edges first, and then adding them to the surface?

AlexW

Hi Ron,

thanks for your reply and sorry for the long break since then.

Your approach will work for sure, but better for a single and less complex hole.

I would like to see a result like in other software, when a obviously more simple way is used to plug the hole. And not to get "a tangled nest of lines".

RonTheSurveyor

No problem about the long break.

This topic intrigued me so I dug into it a bit more and may have found a work-around.

Here is what I did:

• create a surface and TIN from some lidar data
• Deleted some triangles from the TIN to create a hole
• Selected the entire remaining entities in the layer and used advanced creation tools to create a new layer containing lines from the selected areas.
• Created a new surface and TIN from that new layer. Ensured that Use 3d breaklines (hard edge) was checked as well as Flatten 3d area features (though i think that was not a factor). Also checked box to Save TIN as a vector layer.

The results are shown below. The light blue is the TIN that I cut the hole in, and the black is the new TIN.

AlexW

Hey Ron,

so you also reproduced the "bug"?

This is a result i'd expect. Excellent.

Can you (or me) somehow shift this conversation to "Bugs & Errors", so that the developers can take care of it?

sphillips

You can close holes in Meshlab which is free. If you want to do this with Global Mapper you can do the following as a quick and easy workaround.

1. Select the triangles around the hole (no need to be fussy)
2. Generate points from the selected triangles using Create new points from selected area and line features
3. Grid those points ensuring that Save Triangulation Network (TIN) as a vector layer is checked
4. Delete the terrain layer as you don't need it
5. Trim any undesired triangles from the edges
6. Select both layers and export to a new single file e.g. DWG/DXF etc

AlexW

Thanks a lot - this is a proper work around until the bug is fixed. :)

Meshlab (and other external tools) are powerful tools and sometime superior above GM, but i experienced they carry the danger of "error production" when it comes to projections and CRS.