Ben Axelrod wrote on Thursday, September 03, 2009 4:25 PM: > I am trying to view transparent objects inside of other transparent objects. > My objects are simple ShapeDrawables with some color and alpha transparency. > I am seeing strange behavior where the inner object is sometimes completely > hidden by the outer object depending on camera angle. Also, some of the > object edges that should be visible are not. (Again, depending on camera > angle). > > In the attached images: "badalpha.png" there is a small red cube partially > inside of a larger green cube. they both have some transparency and you > should be able to see through both objects. however, some edges of the green > cube are completely hidden by the red cube. The desired behavior can be seen > in "badalphamodbyhand.png" in which I modified to show what should be shown. > > This must be a common problem, but I searched the archives and it did not > turn up much. > > my GL_DEPTH_TEST attribute is on as well as GL_BLEND. I am using OSG 2.6.0 > with an NVidia series 7 graphics card. > > Is there some way to improve the transparency visualization?
This is a common problem: OSG sorts at the granularity of Drawables and according to the bounding sphere's center, so it can get the rendering order wrong from certain points of view (for proper blending, distant transparent objects need to be rendered before nearer objects). For intersecting Drawables, there is no correct order, which is what you're seeing. To get correct behavior, you'd have to split your objects into separate Drawables so that they can be sorted, which may require splitting polygons (and for dynamic objects, splitting the polygons every time the objects move or change shape). HTH, -- Bryan Thrall FlightSafety International bryan.thr...@flightsafety.com _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
