Richard S. Wright Jr. wrote on Monday, December 17, 2007 5:22 PM: > Robert, > > Thanks, yes I have used the Fog approach before, it is especially > effective for underwater scenes. > > However, I need to be able to see quite a ways distant (flight sim). > If I was NOT using a scene graph, I would draw the sky dome as a unit > sphere, and just rotate it by the camera transform, but not translate > it (thus, appearing infinitely distant). I would draw it first, and > not write to the depth buffer. > > Here's where the OSG newbie kicks in... doesn't the scene graph > reorder the nodes at will (ok, I know it's not random, but you get my > point)? Is there a way I have missed to say "this node must always be > drawn first"? If so, I can easily manipulate the matrix of the sky > dome to get the effect I want, and I bet I can turn off depth writing > using the state mechanism. I have however, missed the " draw me first" > flag ;-)
To have the skydome always rendered last, give it a StateSet and call setRenderBinMode(USE_RENDERBIN_DETAILS) and setRenderBinNumber(3). Most stuff uses RenderBin 0, (or 1 and 2 if there's transparent stuff), so this should force it to be last (you can certainly set a higher number if needed). Nested cameras and anywhere else you don't use the default StateSet RenderBinMode will complicate things, though (RenderBins can nest, and the numbers are relative order within the current RenderBin). HTH! > On Dec 17, 2007, at 11:19 AM, Robert Osfield wrote: > >> Hi Richard, >> >> You could play multi-pass tricks like done in the osgdepthpartion >> example, or just manage the visible distance so that the furthest >> distance is never too far away. For instance a common trick is to >> use Fog to make far objects fade away until eventually nothing >> beyond a certain distance can be seen - so you simply cull it and >> this pull in the far plane. The skydome could also be computed >> dynamically to just fits the size of the scene required for that >> frame instead of the whole model. >> >> Robert. >> >> On Dec 17, 2007 1:17 PM, Richard S. Wright Jr. >> <[EMAIL PROTECTED]> wrote: >>> I'm working on my first OSG project (so be gentle ;-) I'm using OSG >>> 2.2 on >>> OS X (Leopard). >>> >>> I have a terrain in a .osga file, a skydome, and some .3ds models. >>> Everything loads fine, and I have a flight sequence working that >>> takes off and lands on an aircraft carrier. >>> >>> There are lots of samples that made this part pretty easy to figure >>> out (just load and move objects around). I'm a little lost however >>> as >>> to how OSG >>> is handling the near and far clipping planes, and object scale. >>> Actually, OSG seems to be monkeying with these settings in a manner >>> that is probably a nice feature once I understand how to best make >>> use of it. >>> >>> The terrain is really big, the skybox is really big, and the models >>> are really small in comparison. OSG seems to recomputing the near >>> and far clipping planes depending on the objects in view. For >>> example, on the deck of the carrier, all is well. If I turn so that >>> the terrain is also in view (off in the distance), the near >>> clipping plane seems to be changed and parts of the carrier >>> disappear (the same happens with the large skydome...) apparently >>> to accommodate the display of the much larger model that is now in >>> view. >>> >>> I did find an old message that says this: >>> >>> >>> Camera- >>>> >>> setComputeNearFarMode(osgUtil::CullVisitor::DO_NOT_COMPUTE_NEAR_FAR); >>> >>> prevents this... however, then I need a giant frustum to hold >>> everything and we all know what a bucket of z-fighting joy that >>> brings. It is not clear to me how to arrange these objects >>> correctly to make this "rescaling" of the scenes objects work >>> correctly. Currently, the terrain database, the skydome, and the >>> ship models are all hanging off the root of the scene graph with >>> just a transform that scales, translates and rotates them as >>> necessary. >>> >>> Is there a 'standardized' technique for this (it can't be that >>> unusual), none of the example programs seem to have this kind of >>> configuration. -- Bryan Thrall FlightSafety International [EMAIL PROTECTED] _______________________________________________ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
