Getting euler angles

[amirsteinitz]

hi,
I am using FreeCAD v0.20 on Windows.
I have a question which should be quite easy to answer but I cannot find the answer.

I have a CAD file and I want to get the Euler angles for a surface vs. the coordinate system

Screenshot 2022-08-16 091727.png (126.73 KiB) Viewed 555 times

when I select (touch) the object this is what I see in the command line:

Python 3.8.10 (tags/v3.8.10:3d8993a, May 3 2021, 11:48:03) [MSC v.1928 64 bit (AMD64)] on win32
Type 'help', 'copyright', 'credits' or 'license' for more information.
>>> # Gui.Selection.clearSelection()
>>> # Gui.Selection.addSelection('Unnamed','Compound','Face1203',2576.49,-389.134,1138.75)
>>>


I searched and looked around and cannot figure how to get the angles for the object.

Thanks

[thomas-neemann]

deleted because wrong

[papyblaise]

I also don't understand why it displays 0.58, 0.58, 0.58 angle 120° when it is parallel to the ZY plane, it should be 0, 1.00, 0 angle 90°

[mfro]

>>> # Gui.Selection.clearSelection()
>>> # Gui.Selection.addSelection('Unnamed','Compound','Face1203',2576.49,-389.134,1138.75)
>>>

To my knowledge, only obtainable from Python. Try (on the Python console's command line):

Code: Select all

print(App.ActiveDocument.Compound.Shape.Faces[1202].normalAt(0, 0))

(note that the name and the array index are off by one, i.e. naming is 1-based while index is 0-based)

This will print the normal vector of the face at (u=0, v=0). If you want the angles to the global coordinate system, you can get it using

Code: Select all

v = pp.ActiveDocument.Compound.Shape.Faces[1202].normalAt(0, 0)
print('toX=', v.getAngle(App.Vector(1, 0, 0)), 'toY=', v.getAngle(App.Vector(0, 1, 0)), 'toZ=', v.getAngle(App.Vector(0, 0, 1)))

(in radians)

[thomas-neemann]

...

is that helpful?

Bildschirmfoto_2022-08-16_14-36-45.png (123.17 KiB) Viewed 435 times

[edwilliams16]

I also don't understand why it displays 0.58, 0.58, 0.58 angle 120° when it is parallel to the ZY plane, it should be 0, 1.00, 0 angle 90°

Not the same:

Code: Select all

>>> rot1 = App.Rotation(App.Vector(1,1,1), 120)
>>> rot2 = App.Rotation(App.Vector(0,1,0), 90)
>>> XAXIS = App.Vector(1, 0, 0)
>>> YAXIS = App.Vector(0, 1, 0)
>>> ZAXIS = App.Vector(0, 0, 1)
>>> 
>>> rot1 * XAXIS
Vector (1.1102230246251565e-16, 1.0, -1.1102230246251565e-16)
>>> rot2 * XAXIS
Vector (2.220446049250313e-16, 0.0, -1.0)
>>> rot1 * YAXIS
Vector (-1.1102230246251565e-16, 1.1102230246251565e-16, 1.0)
>>> rot2 * YAXIS
Vector (0.0, 1.0, 0.0)
>>> rot1 * ZAXIS
Vector (1.0, -1.1102230246251565e-16, 1.1102230246251565e-16)
>>> rot2 * ZAXIS
Vector (1.0, 0.0, 2.220446049250313e-16)

rot1 maps the XY plane to the YZ plane. rot2 maps it to -ZY. Same plane but rotated 90 degrees about its normal.