Scripted objects

[shoogen]

About how to write pickable classes checkout the Python documentation for this.

But there is still some odd behavoir, like the 'Object' attribute of a ViewProvider Proxy gets magicly restored even if i override __setstate__(self,state).

[helo10]

the 'Object' attribute of a ViewProvider Proxy gets magicly restored even if i override __setstate__(self,state).

The Object-attribute gets restored if you do not override get/setstate?
And you initialzid you Object attribute like that?

Code: Select all

    def __init__(self,vobj):
        ...
        self.Object = vobj.Object
        ...

[yorik]

The Object-attribute gets restored if you do not override get/setstate?

No... According to Werner the best way is to setup your Object attribute in the attach() method. Since that method is run on object creation and on file load, you are sure you will always have it present. Another solution is of course to save it with get/setstate, but this is much simpler IMHO

Code: Select all

def attach(self,vobj):
    ...
   self.Object = vobj.Object

[helo10]

thanks yorik,
that was the information I was searching for

[shoogen]

Can anyone explain what the relation between the Object Placement and the Shape.Placement is, why Placements get lost when copying Shapes and assigning them in an execute function and whow to safely do transformations on a shape in a parametric object?
If the base object is a boolean, the shape is fine. If the base object is a primitive i need to manualy do a transformGeometry(baseobj.Placement). This doesn't make any sense to me.

[yorik]

As far as I know things work like this:
- if a shape is bound to an object, their placements are kept in sync automatically.
- if you create a new shape, it always starts with a null placement. adding pieces to it doesn't modify that placement.

I think, if I understand your problem correctly, that the boolean takes 2 shapes, which have each a specific placement, and creates a new shape, with null placement, but constructed with pieces of the 2 objects, which are at correct positions. When you create a primitive from scratch, it always starts at position 0,0...

Usually in parametric objects, I do like this:

Code: Select all

def execute(self,obj):
    pl = obj.Placement
    # construct shape here
    obj.Shape = shape # this has the effect of resetting the object placement to adopt the shape placement (usually null)
    obj.Placement = pl # to restore the initial placement

[shoogen]

Thanks, it seems that removeSpliter loses the Shape.Placement for the Result of booleans.

EDIT: Filed as https://sourceforge.net/apps/mantisbt/f ... php?id=699

[yorik]

hm that's possible indeed. The algorithm probably reconstructs the shape from scratch...

[shoogen]

Is there a safe way to apply a placement to a Shape?
transformShape seems to only modify the Shapes Placement.
transformGeometry expects affine transformations which is not needed in this case.
It takes the current Placement into account but istead of returning the null placement. It modifies the geometry to be relative to the Placement of the old Shape. I had once problems with transformGeometry with the unity matrix. But I can't repruce it right now.
On the other hand implicit dropping the Shape after assignment, like i do with the MatrixTransformation and RefineShape Features in the OpenSCAD module is probalbly bad. And an 'applyPlacement' feature would nullify the Placement.

[wmayer]

Never use transformGeometry() unless you really want to apply an affine transformation other than translations or or rotations (e.g. shearing, scaling, ...) because this always changes the underlying geometry to b-splines. And since boolean operations with splines in OCC are very weak you'll run into a lot of trouble later.

If you have a part feature instance then the "transformShape" of its Shape attribute cannot be used because it's marked as immutable and will throw an exception. So, the fastest way is to apply the placement to the Placement attribute of the part feature. We don't have a method for the feature classes to apply incremental changes on the placement so you have to do that on your own.

Code: Select all

part = App.ActiveDocument.addObject("Part::Feature")
part.Shape = ...
part.Placement = ...
# apply transformation
placement = ...
part.Placement = placement * part.Placement