How-To

How-To#

  • Download or Copy the script in a main.py.

  • Create an ‘output’ folder and a ‘model’ folder.

  • Add the models for test in the model folder.

  • Change the main.py to Load the correct model, before running the code.

IFC Local Coordinates Script#

This Scripts is created to get local placement of all elements in excel. Its based of https://github.com/IfcOpenShell/IfcOpenShell/issues/688 Shoutout to aothm for the base of the code and Moult for debugging it.

Also take a look at this link to understand placement in IFC better: https://pythoncvc.net/?p=851

Output Information#

x, y and z is direction Vectors. t is the translation The last vector [0,0,0,1] is w This defines if the matrix is a diretion or a position in space.

[ x0 y0 z0 t0 ] [ x1 y1 z1 t1 ] [ x2 y2 z2 t2 ] [ 0 0 0 1 ]

Using placement matrix#

As stated in its source code when you create a geom. Its location is given by a 4×3 matrix. But care, when displayed as a tuple IfcOpenShell matrix and FreeCAD matrix are transposed :

IfcOpenShell matrix values is a tuple of 4 consecutive vector’s xyz :
format : (v1.x, v1.y, v1.z, v2.x, v2.y … , v4.z)
FreeCAD matrix constructor takes up to 16 float. 4 vectors grouped by x, y, z values :
format : (v1.x, v2.x, v3.x, v4.x, v1.y, … , v4.z, 0, 0, 0, 1)

About the last 0, 0, 0, 1 of FreeCAD matrix. As greatly stated in matrices chapter from the OpenGL tutorial :

This will be more clear soon, but for now, just remember this :
If w == 1, then the vector (x,y,z,1) is a position in space.
If w == 0, then the vector (x,y,z,0) is a direction.
(In fact, remember this forever.)
http://www.opengl-tutorial.org/beginners-tutorials/tutorial-3-matrices/