I think the technique of seperating the object to CW & CCW direction applies for convex geometry only. It would work if back faces also have multiple layers along the viewing angle. But I guess I'll live with it. suppose I could afford the awefull time consumption of sorting the vertices each frame, would the best place to put it is in the cull traversal as cull callback?
thanks anyway for the replies I've learned much, Guy. ----- Original Message ----- From: "Robert Osfield" <[EMAIL PROTECTED]> To: "osg users" <osg-users@openscenegraph.net> Sent: Sunday, June 24, 2007 11:40 AM Subject: Re: [osg-users] Blending for dummies :) > Hi Guy, > > Sorting Geometry by depth on each frame would be very expensive for > any other than trivial geometry. You don't want to do, and the OSG > doesn't support it either. > > Approaches you can take include: > > 1) Break you geometry into smaller separate osg::Geometry so that > the coarse grained > depth sorting can work more efficiently. > > 2) Use a double pass approach where you draw the back faces first, > then draw the > front faces. You can achieve this by duplicating all your > primitives, swapping the > primitives binding and then ordering them so the reverse > binding are first then > the original bindings. You also need to enable back face culling. > > Robert. > > > > On 6/24/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > > > > > > Thanks to everyone that helped on the issue, > > I also had some more readings about it, but the problem I have is that the > > objects in the transparent bin are sorted by depth against each other but I > > need the vetices to be sorted. > > > > I'm having a drawable which contains many vertices and is transparent, from > > some direction I see through the front of the object it's back correctly and > > from the other direction it doesn't look correct (even when disabling depth > > test, or setting depth mask to true/false), the problem is that the vertices > > aren't drawn in the correct order and so the source alpha and destination > > alpha are swapped. Is their a way to tell osg to sort the vertices of the > > drawable depending on the viewing angle? is it VERY slow? any ideas? > > > > thanks, > > Guy. > > > > ----- Original Message ----- > > From: Paul Martz > > To: 'osg users' > > Sent: Tuesday, June 19, 2007 7:22 PM > > Subject: RE: [osg-users] Blending for dummies :) > > > > > > Any geometries that blend against each other should be in separate > > Drawables, and their StateSet should have the render bin hint set to > > TRANSPARENT_BIN. OSG will then draw these Drawables after all opaque > > Drawables and in back to front order. There are other strategies too, but > > this is the simple common one. > > > > > > For more information, there are many OSG examples that demonstrate how to > > set up OSG for correct rendering of translucent objects. Also, check the > > archives, as this has been covered multiple times recently. > > Hope that helps, > > > > > > Paul Martz > > Skew Matrix Software LLC > > http://www.skew-matrix.com > > 303 859 9466 > > > > > > ________________________________ > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of > > [EMAIL PROTECTED] > > Sent: Tuesday, June 19, 2007 12:15 PM > > To: osg users > > Subject: [osg-users] Blending for dummies :) > > > > > > > > Hello, > > I'm trying to activate blending in some node. I set in the stateset > > GL_BLEND on, and added osg::BlendFunc but it seems to work only from > > backward views. I tried to disable GL_DEPTH and GL_CULL with no better > > results. > > any ideas? > > > > thanks, > > Guy. > > > > ________________________________ > > > > > > _______________________________________________ > > osg-users mailing list > > osg-users@openscenegraph.net > > http://openscenegraph.net/mailman/listinfo/osg-users > > http://www.openscenegraph.org/ > > > > > > _______________________________________________ > > osg-users mailing list > > osg-users@openscenegraph.net > > http://openscenegraph.net/mailman/listinfo/osg-users > > http://www.openscenegraph.org/ > > > _______________________________________________ > osg-users mailing list > osg-users@openscenegraph.net > http://openscenegraph.net/mailman/listinfo/osg-users > http://www.openscenegraph.org/ > _______________________________________________ osg-users mailing list osg-users@openscenegraph.net http://openscenegraph.net/mailman/listinfo/osg-users http://www.openscenegraph.org/
