Inkscape

fixed center of rotation

Asked by Charles Geiler

I often use the rotational center as a snap-able "origin" point for various objects. But if you resize the object, the rotational center automatically moves itself to the new geometric center of the bounding box. Is there a way to keep it from moving itself? Or, is there a better way to do what I'm trying?

It would be awesome to see a user definable snap-able origin or anchor point in future versions.

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Hachmann (marenhachmann) said : 		#1

Hi Charles,

I'm not sure I get entirely what you mean - I assume you already know that rotation centers can be moved? They don't reset when you resize the object (at least not for me), but stay in the same 'relational' position to the object. Of course, they do not stay in the exact same position on the canvas.

If you need to define snap targets on the canvas, you could snap to guide intersections, grids, or create a layer with just 'dots' that can be the anchors, but which you can hide when you don't need them.

As for the feature request, aboud defining 'anchor points' on specific canvas coordinates (which sounds as if it could be useful), can you browse the bug tracker to see if this has been requested before, and if not, add a feature request for it there?

Kind Regards,
 Maren

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Charles Geiler (whozaa) said : 		#2

I didn't describe my problem very well in my initial post. I agree that resizing an object doesn't necessarily move the rotation center.

What I'm asking is if there is a way to make a group's rotation point stay at the exact same point on the canvas when I do a transformation to one of the objects in the group.

I couldn't find an existing feature request for this, but I did find a blueprint (Transformation anchors) which would probably end up covering what I'm asking about.

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Best Hachmann (marenhachmann) said : 		#3

Ah, okay, thank you for clarifying, Charles.

So, the transform center (which is the same as the rotation center) is defined in relation to the object's borders. If a size change is done to a group member by which the size of the whole group changes, then the absolute position of the transform center may change, too. I'm not 100% certain how this is calculated, though...

In that case, in the current Inkscape version, you would need to use one of the workarounds described above to mark the desired center position with guides, or another object. You can use that point to snap the group's rotation center to to get it exact (unfortunately, it doesn't work the other way around, see https://bugs.launchpad.net/inkscape/+bug/1540137).

Kind Regards,
 Maren

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Charles Geiler (whozaa) said : 		#4

Thanks Hachmann, that solved my question.