[osg-users] Flipping the normals
Hello, I've a relatively easy task to accomplish, that is to render a mesh both from inside and outside. To do this i put the mesh under two different Geodes, in one i set the front face to clock wise on the other I set the front face to counter clock wise turning on the backface culling (or putting the object into a single Geode turning off the backface culling). The problem is that in one case (when I render the interior of the mesh) the polygons are not lit since the normals are (of course) not flipped, that is they remain oriented outward. My question is: how can I flip the normals? should I create two distinct meshes, one with the original normals and the other with inverted normals (modifying manually the normal buffers, and doubling the memory usage) or there is a more elegant way to do that, for example a node/state like GL_PLEASE_FLIP_MY_NORMALS that can take care of this task automatically? Cheers, Mike ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Flipping the normals
Hi Mike, Take a look at OpenGL's two-sided lighting support via glLightModel/GL_LIGHT_MODEL_TWO_SIDE (and exposed in OSG with osg::LightModel). I think that's the more elegant solution your looking for. Mike Wittman [EMAIL PROTECTED] mailto:[EMAIL PROTECTED] ___ Seismic Micro-Technology, Inc. 8584 Katy Freeway, Suite 400 / Houston, Texas 77024 Tel. +1 (713) 464-6188 Fax. +1 (713) 464-6440 Web: www.seismicmicro.com blocked::blocked::http://www.seismicmicro.com ___ Seismic through Simulation with KINGDOM, (RC)2, and SURE! - CONTACT US TODAY for more information. From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Michele Bosi Sent: Tuesday, August 28, 2007 4:45 PM To: osg-users@lists.openscenegraph.org Subject: [osg-users] Flipping the normals Hello, I've a relatively easy task to accomplish, that is to render a mesh both from inside and outside. To do this i put the mesh under two different Geodes, in one i set the front face to clock wise on the other I set the front face to counter clock wise turning on the backface culling (or putting the object into a single Geode turning off the backface culling). The problem is that in one case (when I render the interior of the mesh) the polygons are not lit since the normals are (of course) not flipped, that is they remain oriented outward. My question is: how can I flip the normals? should I create two distinct meshes, one with the original normals and the other with inverted normals (modifying manually the normal buffers, and doubling the memory usage) or there is a more elegant way to do that, for example a node/state like GL_PLEASE_FLIP_MY_NORMALS that can take care of this task automatically? Cheers, Mike ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Flipping the normals
Sounds like you want something like: osg::ref_ptrosg::LightModel lightModel = new osg::LightModel; lightModel-setTwoSided(true); myTwoSidedGeode-getOrCreateStateSet()-setAttribuiteAndModes(lightModel.get ()*);* ** Might not be the exact syntax but pretty close. On 8/28/07, Michele Bosi [EMAIL PROTECTED] wrote: Hello, I've a relatively easy task to accomplish, that is to render a mesh both from inside and outside. To do this i put the mesh under two different Geodes, in one i set the front face to clock wise on the other I set the front face to counter clock wise turning on the backface culling (or putting the object into a single Geode turning off the backface culling). The problem is that in one case (when I render the interior of the mesh) the polygons are not lit since the normals are (of course) not flipped, that is they remain oriented outward. My question is: how can I flip the normals? should I create two distinct meshes, one with the original normals and the other with inverted normals (modifying manually the normal buffers, and doubling the memory usage) or there is a more elegant way to do that, for example a node/state like GL_PLEASE_FLIP_MY_NORMALS that can take care of this task automatically? Cheers, Mike ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Flipping the normals
Thanks very much guys, osg::LightModel/GL_LIGHT_MODEL_TWO_SIDE seems exactly what I needed. Thankyou, Mike ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Flipping the normals
Thanks very much guys, osg::LightModel/GL_LIGHT_MODEL_TWO_SIDE seems exactly what I needed. Thankyou, Mike In case it's not obvious, with two-sided lighting you do not need to re-parent your mesh to two Geodes with different face culling. You should be able to use a single Geode, face culling disabled, and two-sided lighting enabled. -Paul ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Flipping the normals
Thanks Paul, just wanted o add that I am very glad that when it comes to render states OSG remains so close to OpenGL and doesn't abstract too much from it, as this case proves, this lets users to reuse their prior knowledge of OpenGL and makes the library really flexible, long life to OSG! :) Mike ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
