Question

hard breaklines

  • 12 October 2013
  • 2 replies
  • 2 views
M
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Hey there,

 

i got stuck on a bit of a annoing problem which i can't seem to find a solution to.

 

 

I am creating a TIN surface for an CityGML modell out of a point cloud using SurfaceModeller. Since i have for example lakes out of a landcover classification which are supposed to just have one flat surface, my idea was to cut all points out of the pointcloud with the lake, force it to 3d and use the outline as a breakline. In my eyes this should result in a perfectly flat surface within the lake and all triangles outside should have one of their sides along the breakline.

 

 

What happens though is what you can see on the picture below. The breakline starts jumping up and down, especially in the corners (rather soft than hard breaklines). I did a lot of research, but couldn't find anything about it.

 

 

So, i would be very happy if you guys could help me.

 

Thanks a lot in advance already for every idea.

 

 

Cheers

 

Matze

 

 

2 replies

A
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Well, as far as you've described it, your logic sounds fine, but there are some bits missing that I don't understand.

 

 

You are sorting out all of the points that are classified as "water" in your cloud, then doing what with them?  Are you using a hullbuilder to find the outline?  How are you forcing the elevation, and how are you picking the one elevation of the lake breakline?
M
Badge
Hey, thanks for your answear.

 

Well i cut out the points within the water. Throwing them out of the model so to speak.

 

I do have the outline of the waterbodies as a polygon.

 

To get the third dimension of the lake i just drape its outline on the pointcloud, get the z bounds extracted and use the 3d forcer to put it to the average height between min and max z values.

 

 

But as i answear i realize how silly throwing out the points inside actually is since a breakline can't really intersect one triangle twice, right?!

 

 

I am on trying this out now. Thanks that far already.

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