CGAL users discussion list

["serg.healthy" <>]

Sorry for my bad english.

I have a lot of 3D models of buildings (more than two thousand) that must be
placed on a map of city (in 3D engine). I know position of each model but
not the angle of model orientation. Also I know 2D polygon which corresponds
to the model. Orient a thousands of models by hand is too time-consuming, so
I would like to somehow automate.

How can i solve this problem? 

3D model of building
http://cgal-discuss.949826.n4.nabble.com/file/n3348109/building.png 


2d polygon which should stand model
http://cgal-discuss.949826.n4.nabble.com/file/n3348109/polygon.jpg 

I think to calc 2D projection of a model and then consistently turning the
projection relative to the initial polygon to find the angle with the
maximum overlap area.

Now I try to solve first part of problem - find 2D projection  of 3D model.
When projecting I want to take into account only the walls of buildings, so
take into account only the triangles whose normal is parallel to the ground.
But I can't get simple polygon from this projection. 

Convex Hull algo i think not suitable. Now I look at 
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Envelope_2/Chapter_main.html
Envelopes of Curves in 2D  and try to understand it.


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