I am trying to extract the geometrical data(height, thickness and radius) from the “Dome” modelled in FreeCAD.
The geometry of the dome is exported as IfcFacetBrep which basically represents the combinations of the coordinates.
How can I extract such geometrical; data from IfcFacetBrep?
You probably ment the IfcFacetedBrep entity, which provides only an approximation of the geometry by describing the body by an approximation of it’s outer an inner shells. By exporting a curved surface in this way, you will loose that kind of geometrical information, so without using some kind of artificial intelligence you won’t be able to get those.
If the dome is spherical, then it’s pretty easy to find the height and radius by visiting every vertex and computing a bounding box. Computing the thickness would require knowledge of what sort of shape you were modeling. I have some ideas about how you might attempt that, but the specifics are left as an exercise for the reader.
Alternatively, you could try to convince the modeling software to export a custom property set that contained the metadata that you need. Or, you could model the dome as two concentric spheres that are sliced with a half space solid.