Not understanding face normals

[sliptonic]

I've run into (another) defect in my basic understanding of FreeCAD.
I created a body with just a simple padded rectangle. Put the body into a Part.
Then select the top face and get the normal.

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>>> face = App.getDocument("Unnamed").getObject("Pad").Shape.Face6
>>> u, v = face.ParameterRange[:2]
>>> face.normalAt(u,v)
Vector (-0.0, -0.0, 1.0)

Then rotate the part. and repeat the process. I still get exactly the same result.
How do I get the normal of the face in its current pose in the global coordinate system?

[openBrain]

How do I get the normal of the face in its current pose in the global coordinate system?

Multiply result by App.getDocument("Unnamed").getObject("Pad").getGlobalPlacement().Rotation

[wmayer]

Then rotate the part. and repeat the process. I still get exactly the same result.

This doesn't change the placement of the shape of the pad at all.

Multiply result by App.getDocument("Unnamed").getObject("Pad").getGlobalPlacement()

Be careful: This is not quite correct. Here the difference of a 3d point and a 3d vector will be relevant as the latter is position-invariant. And this has a consequence in how to compute the face normal of the rotated pad. From the placement you must use the rotation part only but ignore the translation part.

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pad = App.ActiveDocument.getObject("Pad")
face = pad.Shape.Face6

u, v = face.ParameterRange[:2]
n = face.normalAt(u,v)

plm = pad.getGlobalPlacement()
rot = plm.Rotation
rot.multVec(n)

According to your description you only rotate but do not move the Part so that in this special case it would work. But just for fun also move the Part object and then compare the results of

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rot.multVec(n)
plm.multVec(n)

and you will see the difference.

[openBrain]

Be careful: This is not quite correct.

My mistake. Don't know why but I only partially copied the line. I corrected my previous post if someone else comes here. Thanks for vigilance.

[sliptonic]

Perfect. Thank you!

[Roy_043]

Thanks from me as well:
https://github.com/FreeCAD/FreeCAD/blob ... ne.py#L566
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