In fact I was puzzled by the fact that if no directional Light is set in the
scene graph, the one set transversally onto the draw traversal by the osgViewer
(through the cull visitor, ie not in the scenegraph) becomes active. I was
unsure about that indeed, but as you say it's not as soon as at least one light
is present in the scene graph (GL_LIGHT0 == Viewer's HEADLIGHT if and only if
no LightSource is present in the scene).
Debugging a light effect where you can have to deactivate diffuse lights appear
tricky not knowing that. Maybe a default behaviour of the viewer where lighting
is OFF would have been clearer.
Now I have the whole picture thanks to you and Robert, thanks.
-> Effectively, you can merely work into the scenegraph with osgViewer, since
viewer.getCamera()->getOrCreateStateSet()->setMode(..) only activate things on
attributes and modes not encountered in the loaded scenegraph ; those who are
set in the scenegraph aren't reset by osgViewer. So does the osglight example
work.
-> Debugging peacefully an ambient effect can be done : passing through
viewer.getCamera()->getOrCreateStateSet()->setMode(..) works to disable the
'transversal' diffuse light established by the viewer.
-> viewer.setLightingMode() doesn't seem too work well, in v.2.0.0 nor 2.1.10
(it's not vital to me).
Christophe
----- Original Message -----
From: Paul Martz
To: 'OpenSceneGraph Users'
Sent: Thursday, September 13, 2007 4:41 PM
Subject: Re: [osg-users] Lighting behavior and osgViewer::osgViewer
Hi Christophe --
If I'm reading your email right, you have two concerns:
1. You don't understand how SceneView uses its _light member variable.
Without digging into the code, I'm not sure either. But I suspect it
circumvents the typical update/cull traversals and slaps the light state
directly into the positional state of the draw traversal. As _light just
controls GL_LIGHT_0, you don't need to access _light or even its StateSet --
you just need to specify your own alternate values for GL_LIGHT_0.
2. You seem to be unsure that you can fully control lighting and
simultaneously use osgViewer. This is not the case, and again I direct you to
the osglight example program, which uses osgViewer and overrides lighting
effects directly in the scene graph.
Hope that helps,
-Paul
----- Original Message -----
From: "Robert Osfield" <[EMAIL PROTECTED]>
To: "OpenSceneGraph Users" <[email protected]>
Sent: Thursday, September 13, 2007 3:28 PM
Subject: Re: [osg-users] Lighting behavior and osgViewer::osgViewer
Hi Christophe,
I wouldn't recommended messing with SceneView unless you really have to.
osgViewer now honours the Camera's StateSet, and this acts as the
global StateSet. You can simply sets modes and attributes you want on
the camera i.e.
viewer.getCamera()->getOrCreateStateSet()->setMode(..);
Robert.
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