[osg-users] Viewer slaves and RTTs

[Robert Osfield]

Hi Johny,

The  View(er) master Camera has default StateSet assigned to that
initialises OpenGL into an appropriate state for doing typical 3D
rendering via StateSet::setGlobalDefaults().  By replacing the default
Camera my guess is that you aren't assigning your own osg::StateSet
with the appropriate state set to it, so you are just getting OpenGL
defaults which doesn't set up the depth buffer.

Robert


On 17 February 2017 at 19:46, Johny Canes <petrussijsma at gmail.com> wrote:
> Hi,
>
> Sorry for one chunky looking post, but it's actually quite coherent. Can I have your short attention it's very appreciated.
>
> I am trying to use viewer slaves with a chain of render-to-textures. I understand this is best done using several cameras.
>
> I've looked at plenty of resources online as well as all the examples.
>
> I am aiming for a postprocessing setup using a main camera and an orthographic camera that renders a quad to the screen.
>
> I have a main camera that renders the scene, attached as
>
> Code:
> viewer.addSlave( main, osg::Matrix(), osg::Matrix() );
>
>
>
>
> It is supposed to render the 'scene data' as set by setSceneData. This kind of works... but not without peculiar problems.
>
> And my orthographic camera, with a quad as its child, attached as
> Code:
> viewer.addSlave(ortho, osg::Matrix(), osg::Matrix(), false);
>
>
>
>
> One problem is that osgViewer has a default camera, and when I override it with mine using
> Code:
> viewer.setCamera( main )
>
> , the z-ordering goes nuts.
>
> The orthographic is rendering its quad properly though, which has its texture set to the color attachment of the main camera, because my main camera has
> Code:
> camera->attach( osg::Camera::COLOR_BUFFER, texture, 0, 0, false, 0, 0 );
>
>
>
> However, problems remain. I have been outcommenting lines of my code to get nearer to the problem, and random things and unexpected discrepancies are happening as I go.
>
>
> Code:
> viewer.addSlave( camera, osg::Matrix(), osg::Matrix() );
> viewer.setCamera( camera ); // unnecessary / messes up z-ordering ...
>
>
>
> These two lines of code for example. If I switch these lines, the camera will not render (my texture will be black instead of the scene).
>
> Another odd things, is that whilst I've set the color attachment of main, it is still writing to the screen. Sadly, when I tell it to use an FBO, it goes black completely (apparently neither rendering to my color attachment nor the screen).
>
> So I have things working and not working, but currently I am battling some odd behavior that I cannot best.
>
> Cheers,
> Johny
>
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=70235#70235
>
>
>
>
>
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