Date: Feb 20, 2012 8:56 AM
Author: giuseppe
Subject: rotation arownd an axis ,Euler?

My problem is that I must find from a 3d matrix(that is an input from a .ifc file bim) the rotation component around the axis of extrusion vector (that i have).
If you multiply all the 2d profile points for the rotation matrix or if i find the angle with Eulers , is correct only for a beam or column oriented in x/y plane
If i change the extruding direction i change the x,y,z of the multiplied 2d points(the profile of the section)
for example a point is 122,122,0 for the z direction :
0, 122 ,122
or for a y direction:
122, 0 , 122
or x
122,122,0 ecc.......
in the rotation matrix there is the rotation of the profile(around the z axis) and the rotation of the beam profile.
How i can extract only the section rotation angle?
I see that is sufficient get the correct pair of coords , but how i can create an algorithm in c++ that select the correct coordinates pairs?
x,y
x,z
or
y,z?

thanks