I've had the same problem in the past and my solution, purely on the modelling side, was to offset my glow polygon along the axes that points towards the eye (+Y I think). Then the billboard is positioned at the light source but the glow is drawn a little closer towards the eye. So as you look more obliquely, the glow polygon is not immediately clipped in half. It does start to get clipped at some angle but the effect is much less serious. For me it was adequate for all my small lights in the scene and you might need to experiment with the offset distance which depnds on the light size. I used the occlusion method too but only for really bright objects like the sun with lens flare etc.
Regards, Simon _______________________________________________________________________ Simon Mills Modelling & Simulation Section (TEC-SWM) Tel: +31 (0)71 565 3725 European Space Agency (ESA/ESTEC) Fax: +31 (0)71 565 5420 Postbus 299, 2200AG Noordwijk e-mail: [EMAIL PROTECTED] The Netherlands http://simulation.esa.int _______________________________________________________________________ Roderick Kennedy <Roderick.Kennedy@ evos.net> To Sent by: osg users osg-users-bounces@ <[email protected]> openscenegraph.net cc Subject 04/01/2007 17:26 RE: [osg-users] Light point depth Please respond to osg users <[EMAIL PROTECTED] negraph.net> No now I think about it, that wouldn't work. What you need is for the actual depth test to depend on the sprite centre, which can't be done with the usual z-test. Sounds like the occlusion test is the way forward. From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Roderick Kennedy Sent: 04 January 2007 15:57 To: osg users Subject: RE: [osg-users] Light point depth How about a billboard sprite shader that takes z depth from the sprite centre? From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Zach Deedler Sent: 04 January 2007 15:37 To: 'osg users' Subject: RE: [osg-users] Light point depth Hmmm, looks like there is no simple solution. For now, I'll just try to offset the light points more, and put the more elegant solutions on the back burner. Thanks for all the ideas everyone. Zach From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Paul Martz Sent: Thursday, January 04, 2007 10:17 To: 'osg users' Subject: RE: [osg-users] Light point depth I don't care if the light point occludes objects within a few meters. Would using a PolygonOffset work with a meter offset? I believe PolygonOffset won't work for you when viewing the light at an obtuse angle, say from the side, and slightly in front of, the vehicle. In such a case, the further headlight would need a greater depth offset than the near headlight to in order to completely avoid intersecting the vehicle body. In general, whether PolygonOffset produces acceptable results or not varies depending on available depth buffer precision, and how you've set your near/far planes. Paul Martz Skew Matrix Software LLC http://www.skew-matrix.com 303 859 9466_______________________________________________ osg-users mailing list [email protected] http://openscenegraph.net/mailman/listinfo/osg-users http://www.openscenegraph.org/ _______________________________________________ osg-users mailing list [email protected] http://openscenegraph.net/mailman/listinfo/osg-users http://www.openscenegraph.org/
