Re: [openvrml-develop] Navigation in "Examine Mode"

[Chris M. <ch...@ma...>]

Greg Roelofs wrote:
> 
> > All Cosmo did was pick a point in the middle of the bbox and use that as
> > the examine center. Then it was maintained through pan and zoom.
> 
> Ah, but the bounding box of what?  Everything visible within the view
> frustum, only those things completely contained within it, just the
> things within a half-angle view, ... ?  For example, if you have two
> balls, one centered and one to the side, you probably want to rotate
> about the centered one, not about the centroid of the two.  But maybe
> that gets too complicated with special cases.

These are all good questions. I am sure we never did anything "smart".
When we computed the bbox for use as a rotation center, we did the bbox
of everything. But we may only have done that if there was no viewpoint
in the scene. I don't quite remember...

>...It was very easy to grab the object examine all around it and
> > then return it to its original orientation. This is something I have
> > never seen in any of the other browsers.
> 
> Yes, yes, I *loved* that level of control--very nice, and most worthy
> of copying.  The only thing missing (IMHO) was a Cosmo/Live3D body-
> centered spin mode, which was very nice for manipulating building models
> (where you generally want "up" to be "up," regardless).  I can't remember
> what the other mouse buttons and shift keys did in Cosmo, but there must
> be some available combo to which one could bind the secondary mode.

The only thing we had was "straighten" which would turn the camera to
make Y up. I have seen the type of thing you are talking about. In fact,
we did a Blendo demo of a multiresolution earth globe where we used
something like that. It would always rotate about the pole and when you
went north and south, it would simply angle the camera down or up to
keep the earth in the center of the view. Of course, you could never go
further than the pole in this mode. But for viewing this type of model,
it worked pretty well.

--
Chris Marrin          | Senior Software Architect | Sony Corporation
phone: (408) 955-3049 | cm...@ar... |
[ "As a general rule, don't solve puzzles that open portals to Hell." ]
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