Slaves can be moved independently of the main camera by setting their
reference frames to ABSOLUTE_RF. Otherwise, yes, they are offset from
the main camera.

 

Yes, slaves can either share the main graph or may have their own
subgraphs.

 

Typically, yes, though this all depends on what they're being used for.
I have used a slave to provide an orthographic overlay (HUD) projection,
which has its own unique subgraph.

 

A single Viewer should be used when there is a single conceptual view,
while CompositeViewer should be used when there is more than one. See
the Viewer vs. Composite viewer programming guide on the OSG site for
more discussion on this (including usage examples).

 

Matthew W. Fuesz

Software Engineer Asc.

Lockheed Martin STS

1210 Massillon Road

Akron, OH 44315

[EMAIL PROTECTED]

 

________________________________

From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of
[EMAIL PROTECTED]
Sent: Monday, August 04, 2008 12:21 PM
To: osg-users@lists.openscenegraph.org
Subject: [osg-users] Viewer/CompositeViewer

 

I'm starting to convert several apps from OSG 1.X to the current
release.  I've read the posts regarding Viewer and CompositeViewer and
want to make sure I'm understanding it right.  If you don't mind a few
beginner questions...

 

1)  Viewer (which "is a" View) can have one or more Cameras, but if
using multiple Cameras, they are positionally slaved to the single View
Camera by offset matrices, right?

 

2)  The slaved Cameras can share the subgraph (Scene) below the View
Camera, but if desired, they could have their own subgraphs?

 

3)  It seems that generally, since the slaves are offset from the View
master camera, for most applications, they would share the same Scene,
right?

 

4)  CompositeViewer (which "contains" Views) can be more flexible since
each View Camera can be independently positioned (i.e., different views
of the same Scene, but where Camera 2 doesn't necessarily follow Camera
1).

 

5)  The View(s) within a CompositeViewer could themselves be
single-Camera or master-slave configurations.

 

6) It seems that a CompositeViewer with a few Views could be
functionally equivalent to a "Viewer with slave Cameras" provided the
user positions the CompositeViewer Views with respect to a designated
"master" View in real-time?

 

7)  I see some efficiencies, such as a master-slave View applying the
Update traversal only once to the shared Scene.  Are there any other
significant benefits (e.g., cull, rendering, state) that make a Viewer
master-slave setup more efficient than the equivalent manually-slaved
Views in a CompositeViewer?

 

Sorry for the length, but I hope this post might be useful to others
just starting the 1.X to 2.X conversion.

 

Thanks!

Dan Guinther

 





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