# Extracting surfaces and areas from the triangulated surfaces of a building

Hi,

I am relatively new to Dynamo and this forum. Thus, sorry, if not following any proper conventions. I am writing to have inspiration on developing the solution for the following problem. In Estonia, we have the national digital twin system as shown in the picture below with LOD2 level geometry.

From this digital twin system, IFC files for buildings and terrain can be downloaded. However, the geometry is pretty dumb and comes in the form of triangulated surfaces, which have problems and errors in them. Here is the example file I am working on now and Revit21 file:
https://livettu-my.sharepoint.com/:u:/g/personal/ergo_pikas_ttu_ee/EbLCuZwOl5NJiiv3yePhBFIB63lJAFL-aTDWkKffo5t6PQ?e=85ZhBr

For making energy consumption calculations of buildings in the selected, which is the main end goal, I need to identify surfaces and calculate areas for the walls, roofs, and floors on the ground of each building. The issues in doing that include, 1) how to identify which triangular surfaces are coplanar (needs to be resilient as there are issues in the geometry); 2) how to create a new surface from coplanar trinangulated surfaces; 3) how to categorize new surfaces into different categorize: wall, roof, and floor; and 4) how to sub-categorize walls and roofs according to different orientation: North, North-East, Eastâ€¦

Any suggestion on how to approach the issue, what methods and techniques to use, would be highly appreciated. I have started to test some ideas out myself, through calculating distances to the plane
and checking the angle between surface normals, but this far no solution yet.

Hello @ergo.pikas and welcome to the Dynamo forum

â€¦here is an example for one of your buildings it could be a startâ€¦

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Hi @sovitek, thank you. This is a very good hint and the starting point.

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