Triangulation patterns in .ifc file format using coordinates and indexes

Apr 2018
I have an .ifc format which is a CAD format, and it describes a wall in the xy plane by a set of coordinates and their corresponding indexes according to the link explanation:


I am attaching a .txt where the data is divided into the coordinates in xyz space, then indexes and some other data.

I was hoping that someone can help me understand how to link the indexes to their corresponding coordinates. There are 164 coordinate pairs and 324 index pairs so it doesn't make sense to me that each index relates to only 1 coordinate pair.

The goal is to establish a relationship between indexes and coordinates such that this type of data can output the wall thickness, which is in this case '10'. I was thinking that (according to the link above) by taking the first triangle described, it should describe the edge of the wall in 3D and therefore give us one of its sides as the shortest segment in the wall which is the thickness.

Thank you



MHF Helper
Sep 2012
Hey yafim.

You might want to consider expanding out each coordinate in terms of X's, Y's, and Z's [instead of (X,Y,Z) triples) and then use every index triple to get the actual coordinate for the individual coordinate instead of one triple.

So for example you have X[], Y[] and Z[] and you have an index (a,b,c) then you find X[a], Y, and Z[c] not Point(a,b,c).
Apr 2018
Hi chiro,
Thanks for the reply.

Can you explain what you mean by "actual coordinate for the individual coordinate" ? it's a bit confusing.

What I understand from your explanation is that the actual coordinates might be related to three indexes per each X Y and Z value, correct?