[osg-users] placing image on scene

[Bryan Berg]

Can I clarify than if a cull callback gets called for a node, that means the
node will 

be visible ?

 

 

Would than the boolean

 

node.getCullingActive;

 

tell you if a cull callback has been called ?

 

If so do I have to initialize a cull callback for a node I'm trying to watch
(cause I would think culling is done automatically)

 

Thanks!

 

-Bryan

 

 

-----Original Message-----
From: osg-users-bounces at lists.openscenegraph.org
[mailto:osg-users-bounces at lists.openscenegraph.org] On Behalf Of Robert
Osfield
Sent: Wednesday, April 16, 2008 10:13 AM
To: OpenSceneGraph Users
Subject: Re: [osg-users] placing image on scene

 

On Wed, Apr 16, 2008 at 5:42 PM, Bryan Berg <bberg at spawar.navy.mil> wrote:

> So my question is: how can I take a specific point of the scene and than

> 

>             a)determine if it is to be viewed

 

A cull callback only gets called if the node hasn't yet been culled so

its one way of determining visibility.  Its not 100% accurate as

bounding volumes are larger than the model they enclose so its overly

conservative.  The only 100% reliable way is to render the objects and

use the OpenGL occlusion query extension to find out how many pixels

are visible.

 

>             b)if so, which window coordinate it corresponds to

 

>From within a cull callback you get get the accumulated modelview,

projection and window matrices that you can use to project the local

object coords into window coords.

 

Robert.

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