TransformGeometry Ruins Contents

[duckmug]

I am having a bit of a difficulty with a macro that I am working on.

I am able to manipulate the true location of a wire by doing this:

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m = FreeCAD.Matrix()
m.move(obj.Shape.BoundBox.Center * -1)
new_shape = obj.Shape.transformGeometry(m)

Unfortunately if I convert this to a sketch afterwards, everything will get parsed as a b-spline rather than lines as lines, arcs as arcs etc.

If I convert the wire to a sketch prior to doing this, everything gets parsed correctly.

Is there a way to do the exact same thing without this side effect?

[Chris_G]

Hi,
It is clearly stated in the transformGeometry() doc :

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help(Part.Shape.transformGeometry)

Help on method_descriptor:

transformGeometry(...)
Apply geometric transformation on this or a copy the shape.
transformGeometry(matrix) -> Shape
--
This method returns a new shape.
The transformation to be applied is defined as a 4x4 matrix.
The underlying geometry of the following shapes may change:
- a curve which supports an edge of the shape, or
- a surface which supports a face of the shape;

For example, a circle may be transformed into an ellipse when
applying an affinity transformation. It may also happen that
the circle then is represented as a B-spline curve.

The transformation is applied to:
- all the curves which support edges of the shape, and
- all the surfaces which support faces of the shape.

Note: If you want to transform a shape without changing the
underlying geometry then use the methods translate or rotate.

So you should have better luck with methods translate(), rotate() and transformShape()

[duckmug]

Thanks a lot! I will run that help command in the future.

Update: I've tried that now both with translate and transformShape and it complains:

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ReferenceError: This object is immutable, you can not set any attribute or call a non const method

Is there any workaround to this?

[openBrain]

You can get a separate instance of the shape with

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obj.Shape.copy()

[duckmug]

Perfect, thank you!

[heda]

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>>> App.ActiveDocument.addObject("Part::Box","Box")
>>> App.ActiveDocument.ActiveObject.Label = "Cube"
>>>
>>> ## use gui to move box out of 0,0,0 for demonstration purpose
>>>
>>> App.ActiveDocument.Box.Shape.BoundBox
BoundBox (-15, 10, 0, -5, 20, 10)
>>> App.ActiveDocument.Box.Shape.BoundBox.Center
Vector (-10.0, 15.0, 5.0)
>>>
>>> ## using Draft.move to translate objects
>>>
>>> import Draft
>>> obj = App.ActiveDocument.Box
>>> center_vector = obj.Shape.BoundBox.Center
>>> center_vector
Vector (-10.0, 15.0, 5.0)
>>> center_vector*-1
Vector (10.0, -15.0, -5.0)
>>> Draft.move(obj, center_vector *-1, copy=False)
<Part::PartFeature>
>>> App.ActiveDocument.recompute()
0
>>> ## not sure if you have mentioned what the starting point
>>> ## of the problem is and the desired end state
>>> ## like, "move line from a to b", "mirror wire and translate", etc

[duckmug]

Thanks for the example!