Re: Re : SPEC - 3d menus

Len Wanger ([email protected])
Thu, 27 Apr 1995 13:32:42 -0700 (PDT)

Thr problem with keeping orientation by attaching as a sub-tree of the
camera is that you can have multiple cameras in a scene. In the case of
multiple cameras where do you put the menu? The
annotation/separator/whatever node would maintain that the orientation is
always for the current camera.

Len Wanger -- [email protected]
Interactive Simulations Inc.
http://www.intsim.com/~isigen

On Thu, 27 Apr 1995, steve wrote:

>
> > Actually it would be neat to be able to make any object (or subtree)
> > always face the user, opposed to just text. The problem is that a
> > transformation that changes with the viewpoint is not something we can
> > currently encode into the scene. Perhaps a different solution to the
> > same problem would be to add an fixed_orientation field to the
> > coordinate3 node, that would render any nodes that inherit from it such
> > that their orientation remains fixed as the viewpoint changes. This
> > would work for both 3D text and would be really handy for things ike
> > floating 3D menus that you want to face the users so their always
> > pickable.
>
> The best way to implement 3D menus (or more generally objects that
> must always face the user, and keep up wit the user as they navigate
> around in space), is to 'attach' the menu objects to the head.
>
> If both the orthographicCamera and perspectiveCamera nodes allow
> child nodes (seperator, WWWAnchor etc.) then such objects can be 'attached'
> to the user's head - the objects are transformed as normal, but
> always inherit the position/orientation of the viewpoint.
>
> The main problem is that in this case, these menu objects are always
> in view - this can introduce some visibility problems, when you
> cannot see the actual world for the menus in front of you! Enabling
> and disabling visibility could be done using the switch statement -
> switching to a NULL child effectively disables the other child
> (the individual browsers would have to implement the control of this
> switch statement as there are no interactions defined yet) an
> interactive 'toolbox' can be implemented.
>
> >>-------------------------------------<<
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> Director of Technology
>
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