FreeCAD 0.17R10088 breaks Screw-maker

[ulrich1a]

The commit https://github.com/FreeCAD/FreeCAD/comm ... 66d8cc7204 breaks the screw placement in Screw-maker.
The following code does not move the screw into its place anymore. Is this intended with the commit, or is this a bug?

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          pl = FreeCAD.Placement()
          pl.Rotation = (normvec.x,normvec.y,normvec.z,cos_res) #Drehungs-Quaternion
          neuPlatz = ScrewObj_m.Placement
          neuPlatz.Rotation = pl.Rotation.multiply(ScrewObj_m.Placement.Rotation)
          neuPlatz.move(Pnt1)

Ulrich

[DeepSOIC]

This is a fundamental problem as far as I understand. When you read out something.Placement, it is actually returns a copy of something's placement, which remembers that it's an attribute of object.

If you read out something.Placement again, a new copy will be returned, and the old copy will lose connection to "something". It may be very tricky to fix... Let's see what Werner thinks.

[wmayer]

Sorry for the late reply but I didn't notice this thread earlier.

Based on your code snippets I put together this example which worked in 0.16 as you expect it.

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ScrewObj_m=App.ActiveDocument.addObject("Part::Box","Box")
App.ActiveDocument.recompute()

pl = FreeCAD.Placement()
pl.Rotation = (1,1,1,0.5) #Drehungs-Quaternion
neuPlatz = ScrewObj_m.Placement
neuPlatz.Rotation = pl.Rotation.multiply(ScrewObj_m.Placement.Rotation)
neuPlatz.move(App.Vector(2,4,6))

But now look at this example

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ScrewObj_m=App.ActiveDocument.addObject("Part::Box","Box")
App.ActiveDocument.recompute()

pl = FreeCAD.Placement()
pl.Rotation = (1,1,1,0.5) #Drehungs-Quaternion
neuPlatz = ScrewObj_m.Placement
neuPlatz.Rotation = pl.Rotation.multiply(ScrewObj_m.Placement.Rotation)
ScrewObj_m.Placement = FreeCAD.Placement()
neuPlatz.move(App.Vector(2,4,6))

It has only one additional line

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ScrewObj_m.Placement = FreeCAD.Placement()

to overwrite the old placement so that neuPlatz isn't the placement of ScrewObj_m any more. But the code still shows the same effect because internally neuPlatz still knows about its previous "parent" object and thus applies the transformation to it which is clearly wrong.

To fix your problem with the new version you have to explicitly assign the placement again at the end

Code: Select all

ScrewObj_m=App.ActiveDocument.addObject("Part::Box","Box")
App.ActiveDocument.recompute()


pl = FreeCAD.Placement()
pl.Rotation = (1,1,1,0.5) #Drehungs-Quaternion
neuPlatz = ScrewObj_m.Placement
neuPlatz.Rotation = pl.Rotation.multiply(ScrewObj_m.Placement.Rotation)
neuPlatz.move(App.Vector(2,4,6))
ScrewObj_m.Placement = neuPlatz