Re: fltk backend fix & mouse wheel scroll factor

[John Swensen]

On Sep 27, 2009, at 4:16 AM, Søren Hauberg wrote:

> søn, 27 09 2009 kl. 09:12 +0300, skrev Shai Ayal:
> > The attached changset fixes a bug which did not show the zoom box.
> > Also added a function to enable the user to control the zoom factor
> > when using mouse wheel zoom.
> >
> > I think that with this changeset, the fltk_backend is quite usable as
> > a viewer to the gl-renderer.
>
> I think this is really nice. With this changeset, the FLTK backend is
> very nice to use for 2D plots (much better than both gnuplot and
> matlab).
>
> > I am open to feature requests.
>
> Well, then I'm gonna file a request :-) It would be great to have  
> better
> support for navigating in 3D. Basically, I think dragging the mouse
> should make 3D plots rotate around some point (center of mass?), while
> scrolling should change the distance between the camera and said  
> point.

I have always been a big fan of how the 3D solid modeling programs  
(e.g. ProE and SolidWorks) do their 3D navigation.  The way I see it  
working with Octave is as follows.  There would be 4 different "views"  
available from the plotting window.  Views 1-3 would be associated  
with looking at the plot along each of the cardinal axes.  The four  
would be the "working view".  The user has 2 options regarding how the  
object rotations (or the camera rotates about the object).  The first  
is based on a center of mass idea as you indicated.  This works great  
for solid modeling, since objects have a clear center of mass, but for  
plotting it is more difficult since it becomes not obvious how to  
weight things like lines.  A cloud of points would be easiest to  
implement this behavior.  The second way that solid modeling programs  
work is to allow you to set the center of rotation by switching to the  
3 orthogonal views to set the point of rotation.  Then, you can return  
to the "working view" and rotate and pan as would be expected.  This  
would be harder to implement, and I'm not exactly sure how this meshes  
with how the property tree manages camera position, but I think it  
would help keep from grumbling and muttering unspeakable things every  
time I try to rotate and pan in both Matlab and Octave.

John Swensen