Re: [openvrml-develop] Obtaining the viewpoint frpm OpenVRML

[Braden M. <br...@en...>]

On Mon, 2003-12-29 at 16:05, Ricky Hussmann wrote:
> I need to network three browser clients together. The
> first client will be facing "forward", the second
> "left", and the third "right." All browsers will be
> located at the same position. The viewer facing
> forward I will refer to as the Master. The master
> needs to send viewpoint information to the other two
> clients so that they can adjust their viewpoint so
> their views are left and right with respect to the
> master's view.

Unfortunately, OpenVRML isn't really set up to support a "1 scene : n
viewers" configuration. As it's currently implemented, openvrml::browser
expects to be used with no more than one openvrml::viewer at a time.

> I've looked through the documentation, and it appears
> that I can use the set_viewpoint method of the
> openvrml::glviewer class to set the viewpoint.
> However, I can't find how to obtain the viewpoint
> information from the master. So, basically I need the
> master to send out its viewpoint information (position
> and orientation, whatever), adjust it, and set that
> adjusted information as the viewpoints for the other
> two clients. I do not want to deal directly with
> OpenGL's matrix for fear of running into
> synchronization problems. I'm sure OpenVRML provides
> the features to read, transform, and set the
> viewpoint, I'm just not sure how.

The "master" is the actual scene graph, which is accessible via browser.
Specifically, browser::active_viewpoint gives you the currently "active"
viewpoint_node. (The "active" bindable node is the one at the top of the
bound node stack.) The problem you'll run into is that the rendering
process calls viewer::set_viewpoint in order to put the user view in the
right spot.

If you're interested in modifying OpenVRML to support multiple viewers,
that's a worthy pursuit. It will require devising a strategy to
generalize the notion of a "view" apart from the "user view" (as defined
by the VRML97 spec). Currently the latter is all that's supported.

-- 
Braden McDaniel                           e-mail: <br...@en...>
<http://endoframe.com>                    Jabber: <br...@ja...>