[vtkusers] Modifying actor rotation behaviour

[Zamir Khan]

Argh! I really thought I had looked through the widgets - I think that 
was before I started calling what I was building a "compass" ;)

Thanks Jeff, I will see if that widget meets my needs.

Jeff Baumes wrote:
> On Fri, Dec 18, 2009 at 11:11 AM, Zamir Khan <zkhan at modusmed.com> 
> <mailto:zkhan at modusmed.com%3E> wrote:
> > Hi,
> >
> > I am using VTK to build what is likely best described as a compass 
> control.
> > A 2-d dial with labels and arrows. Most of the control is fixed in 
> position
> > (and the camera is fixed to view the X-Y plane only), but I want to 
> allow
> > the user to rotate the arrows about the center of the compass. Here 
> is where
> > I am running into problems. I need to:
> >
> > 1) Modify the arrow actor such that its rotation occurs about the 
> bottom of
> > its shaft rather than the center of the actor. However, it appears 
> thus far
> > that setting the origin of the actor merely moves the actor to another
> > location in the scene, where it still rotates about its center. Am I
> > misusing SetOrigin, or is there another way to make an actor rotate 
> about a
> > point that is not its center, when manipulated by the user?
> >
> > 2) Limit the rotation of the actor to stay within the x-y plane. My 
> first
> > thought is that I'll need to add an event handler to the appropriate
> > callback for this actor, modifying any rotations to only rotate the 
> object
> > about the z-axis. Is there a better way? If not, if someone has done
> > something similar before, what event would you recommend intercepting?
>
> I'd suggest you take a look at vtkCompassWidget in VTK/Geovis.
>
> Jeff
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