Gordon Tomlinson wrote on Thursday, April 19, 2007 10:32 AM: > Even BSP's don't solve all the problems and they are still pretty > much view dependent ;( in any complex scene > > And you modelers will curse you to the end of time modeling to BSP, > lets say a pain :( > > Until we can afford to sort at the poly level this will not go away ( > even then its not just a sort issue), > > We need the 'Binford Power MKIII Sorter" ... More power ......
A strict BSP isn't really necessary; you just need a hierarchy of separating planes to precisely define the order of transparent objects from any particular point of view, right? I shouldn't have used "BSP" as a shorthand for what I really meant ;) Yeah, it's view-dependent, and it only helps with the static parts of scenes (you have to recalculate the separating planes when things move around); are there any problems with this approach I'm missing? Also, my inexperience with the modelling side is showing, but why do the modellers need to take BSPs (or just the separating planes) into account? Is it because a BSP needs to split the geometry in the scene (which I don't think would be a problem with just separating planes)? > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Thrall, > Bryan Sent: 19 April 2007 16:14 > To: osg users > Subject: RE: [osg-users] translucent objects disappear > > Paul Martz wrote on Thursday, April 19, 2007 9:58 AM: >> Good analysis. >> >> It occurs to me that there might be room for an enhancement to the >> back-to-front sorting in the transparent bin such that it sorts based >> on minimum distance rather than bounding volume center. >> -Paul > > That would be an improvement in some cases, but not in others (for > example, a very large polygon with one nearby vertex and a smaller > polygon farther than that vertex but nearer than all the other > vertices of the large polygon). Unfortunately, pretty much whatever > generic sorting strategy you use will have issues. > > What we really need is a BSP for the transparent stuff; that would > ensure that they are always rendered in the right order. But that > would require (1) a Nodekit for BSPs and (2) scenegraphs properly > built with the BSPs. I'd love to do (1), but I have no time :( > >>> -----Original Message----- >>> From: [EMAIL PROTECTED] >>> [mailto:[EMAIL PROTECTED] On Behalf Of Paul >>> Speed Sent: Wednesday, April 18, 2007 9:32 PM >>> To: osg users >>> Subject: Re: [osg-users] translucent objects disappear >>> >>> (Two Pauls double-teaming...) >>> >>> I believe this comes down to the brute force way that OSG sorts >>> drawables in the transparent bin. This is not always sufficient to >>> ensure proper rendering order... and there's really not much OSG can >>> do about either. At least not and still render in real time. >>> >>> If all of one type of object is inside of another and is frequently >>> obscured by the outer object then you can use the bin numbers >>> (setRenderBinDetails if my memory is good) to make sure the inside >>> objects are always drawn before the outer. The problem you see >>> happens because the outer object is drawn first and fills the >>> Z-Buffer... when the interior objects go to draw they are obscured >>> since the z-buffer doesn't know about that. >>> >>> Hopefully that isn't review. I think everyone on this list has hit >>> this one time or another and the work-arounds always depend on the >>> situation. Sometimes controlling rendering order with the >>> relative bin numbers is a work-around. >>> >>> -Paul -- Bryan Thrall FlightSafety International [EMAIL PROTECTED] _______________________________________________ osg-users mailing list [email protected] http://openscenegraph.net/mailman/listinfo/osg-users http://www.openscenegraph.org/
