From mdsumner at gmail.com  Thu Nov  5 05:30:00 2015
From: mdsumner at gmail.com (Michael Sumner)
Date: Thu, 5 Nov 2015 04:30:00 +0000
Subject: [Rd] navigation mode(s) in rgl
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	<563AC685.4070901@gmail.com>
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On Thu, 5 Nov 2015 at 14:01 Duncan Murdoch <murdoch.duncan at gmail.com> wrote:

> On 04/11/2015 6:56 PM, Michael Sumner wrote:
> > Hello, I've CCd' Duncan Murdoch as the rgl maintainer, but I'm also keen
> to
> > hear from the broader community of any insights.
> >
> > In rgl my understanding is that there's only one rotation-navigation
> mode,
> > where you left-click hold and the view pivots abound the centre of the
> > scene.
>
> That's not quite true:  there are several modes built in, and the
> possibility of adding your own.
>
> > In other tools, including Google Earth, that is the default behaviour but
> > there's also a click-centric mode where the view pivots about the point
> > clicked on.
> >
> > I haven't found the right terminology for this, but I call it
> >
> > 1) Data-centric navigation, rotating about the centre of the data in  the
> > scene (invoked by left-click-drag in rgl and GE and others)
> > 2) Click-centric navigation, rotating about the point clicked on (invoked
> > by centre-click-drag in GE and others, but not rgl)
> >
> > My questions:
> >
> > 1) I'd appreciate any guidance on my terminology here, whether I'm making
> > sense and ask for pointers to resources that explore this properly
> > 2) Is there scope to add this "click-centric" navigation to rgl? I'd
> > appreciate any pointers to how it could be done - is it an rgl-level
> > feature, or deeper down?
>
> If I understand your description properly, you can add it using the
> "user" mouse mode (see ?par3d).  You should also see that help topic for
> a description of how rendering is done, and ?rgl.setMouseCallbacks
> for an example of doing it.
>
> The hard part in doing this is in working out *exactly* what you want
> the mouse to do.  If you work that out for the mode you want but find
> the "user" mode is unsatisfactory for some reason, I'd be willing to add
> it as another built in mode.
>
> Duncan Murdoch
>
>

Thank you, I can see the way forward now.

Cheers, Mike.




> >
> > I know that "click-centric" clicked-on point has a different meaning in
> > different contexts, in GE clearly it finds the nearest point intersecting
> > the globe surface since that is a always-present structure, but other
> tools
> > must have rules to specify where the pivot point is - either
> intersecting a
> > data element or somewhere in the scene.
> >
> > The data-centric mode is fine for small scenes with a limited scope, but
> > when the extent covered by data is large it's quite unwieldy to focus in
> on
> > specific parts of the scene. I know this could be controlled by
> > pushing/popping elements in the scene but the navigation mode obviously
> > offers more flexibility.
>
>
>
>

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[Rd] navigation mode(s) in rgl
Michael Sumner