Hi Murray
In my experience this looks like a classic transparency sorting issue/problem when you have objects that have transparency and their objects bounding volumes intersect,( I would also say this has little to do with you using open flight) This happens because for efficiency scene graphs sort transparent object at a geode level and not at a polygonal level, you find this has been discussed many time in many places If you look at you model its likely that you Rotors are in one object and then the windows/glass in another ( you might have more), is you the think of their 2 bounding spheres they will be intersecting, so as you view changes then how that are possibly sorted will change hence you get the punch through effect you see. One way to try to minimize this is to try and ensure when you create a model you don't create overlap transparency that overlap, this can be challenging to do depending on what you are modeling (you also have to watch for optimizers in Scenegraphs that try to chunk like materials and texturing in to one group as this can artificially introduce overlaps) You can also try to use a an opaque texture to represent windows/port holes (do you really need them to be transparent?) to help. You can create you own render bin that sorts at the triangle level for these models Gordon Tomlinson 3D Technology System Engineering Consultant Overwatch(r) An Operating Unit of Textron Systems __________________________________________________________ "WARNING: Documents that can be viewed, printed or retrieved from this E-Mail may contain technical data whose export is restricted by the Arms Export Control Act (Title 22, U.S.C., Sec 2751, et seq,) or the Export Administration Act of 1979, as amended, Title 50, U.S.C., App. 2401 et seq. and which may not be exported, released or disclosed to non-U.S. persons (i.e. persons who are not U.S. citizens or lawful permanent residents ["green card" holders]) inside or outside the United States, without first obtaining an export license. Violations of these export laws are subject to severe civil, criminal and administrative penalties." From: [email protected] [mailto:[email protected]] On Behalf Of Murray G. Gamble Sent: Wednesday, February 23, 2011 2:37 PM To: OpenSceneGraph Users Subject: Re: [osg-users] Draw Order/Culling with OpenFlight and Transparency Thanks for the suggestion, Chuck. I've tried this, and do not observe any appreciable improvement in rendering. I should point out that while the images I provided highlight the main rotor disc as the offending geometry, there are numerous other geometry elements (e.g., windows) that cause similar issues when viewed from various angles. I've stepped through the OpenFlight loader in debug mode and have observed that the rotors and windows are both being caught by the tests therein for translucent images and transparent materials, respectively. These tests result in the state sets being set as you've suggested, so it appears that OpenFlight loader is treating these nodes correctly. Any other ideas? Murray On 2011-02-23, at 1:57 PM, Chuck Seberino wrote: Murray, Your rotor is being placed in the Opaque render bin, which is causing all of the geometry behind it to be culled out. You need to make sure it is in the transparent bin. You should add these to the stateSet of the rotors: stateSet->setRenderingHint(osg::StateSet::TRANSPARENT_BIN); stateSet->setMode(GL_BLEND, osg::StateAttribute::ON); HTH, Chuck On Feb 23, 2011, at 10:53 AM, Murray G. Gamble wrote: Hi All, We have an OpenFlight model of a helicopter that exhibits some undesirable rendering behaviour in OSG. Specifically, various parts of the helicopter geometry are being culled and/or rendered in the wrong order. We do not observe this behaviour when rendering the same model using Vega Prime. I've attached a couple of screen captures that exemplify the issues. Can users with similar experiences provide any suggestions as to how to avoid these rendering artifacts? Does the model component/geometry hierarchy need to be modified and/or are there programmatic things that can be done within our OSG application to remedy the situation? I'm using OSG 2.8.0. Many thanks, Murray <CH149-OSG.jpg><CH149-VP.jpg> _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or g _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.or g -- Murray G. Gamble, CMSP Director of Modeling & Simulation VSIM / Advanced Cognitive Engineering (ACE) Lab 2227 V-SIM, Carleton University Ottawa, Ontario, K1S 5B6 off: 613.520.2600 x2475 cell: 613.298.0997 fax: 613.520.2539 e-mail: [email protected] <mailto:[email protected]> http://acelab.carleton.ca
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