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

[S.K.Bose <bo...@pa...>]

On Wed, 5 Sep 2001, Chris Marrin wrote:

> The really cool thing about Cosmo's examine mode (which I have not seen
> duplicated anywhere else), is the manipulation interface. It used a
> manipulator from Inventor called a "SphereSheetProjector". This was a
> very nice class which would take the pick point and project it onto
> either a sphere or plane (sheet) depending on its distance from the
> center of rotation. Near the center of rotation, the object is
> manipulated as if your hand was on a sphere, very natural. But as you
> moved off the center, it became more and more as though you were
> dragging a piece of string along a flat surface (the sheet). The other
> end of this string was wrapped around the object, which spun along an
> axis perpendicular to the direction of drag as you moved away. It solves
> many of the problems of manipulation and makes for very repeatable
> results. 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.
>

If I am right, You are talking about "Virtual Trackball". Now this Virtual
Trackball is being used for our Navigation in Examine Mode. This Virtual
trackball is Copyrighted by Silicon Graphics. Chris Morley is the best
person to tell about this hacked portion. This code was implemented by
Gravin Bell, lots of ideas from Thant Tessman and  the August '88 issue of
Siggraph's "Computer Graphics," pp. 121-129.

Thanks,

Bose