Re: [osg-users] Questions about physic engines.
On Monday 08 February 2010 09:38:53 pm Paul Martz wrote: Ricardo Ruiz wrote: Thanks. Just one question, OSG renders at the maximun amount of FPS it can, but ODE requires a fixed time step. How do you solve this problem? Thanks a lot. Is there a reason you're not synced to vertical swap? If you were to enable that, then OSG would render at the refresh rate of the monitor (unless you have a huge rendering load). Assuming you use the monitor refresh rate as the ODE simulation interval, then the two sample rates would match. End of problem. I'm not sure my Bullet work will help here, as Bullet doesn't require a fixed time interval. You just pass an arbitrary elapsed time interval to stepSimulation and Bullet produces sim results accordingly. osgBullet (at http://osgbullet.googlecode.com) includes a mechanism to share transform data between separate rendering and physics threads, allowing both to run at whichever rate they choose (not to mention take advantage of multicore systems). So if you can't find any way for ODE and OSG to use the same sample rate, then a mechanism like this might help. I seem to recall someone making some changes to osgViewer a while back to control the frame rate. I didn't really follow that change or discussion. Maybe just looking at the source code would be revealing. -Paul ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org Hi, I'm working on a project (work in progress, still growing) which combines bullet and osg. Currently there are only rigid bodies and I'm not using osgBullet or osgPhysics. What I've done so far: - separate threads for bullet and osg - usage of btDiscreteDynamicsWorld - a loader which loads 3d objects and calculates simplified collision bodies Any loaded 3d object is attached to the OSG-graph and its collision body is attached to the DynamicsWorld. The physics thread runs at a high frequency while the gfx-thread is synced to the vertical swap. Even if vsync is off you can implement a frame limiter by measuring the time a single frame needs to be calculated. You can then put the gfx thread to sleep (OpenThreads::Thread::microSleep()). You can calculate the frame-time in the same way for the physics-thread. Use this value as simulation step. The high update rate of the physics thread prevents punch-through effects for fast moving objects. The transform data of the collision bdoy is read from the gfx-thread in an OSG update callback. You may have to sync both threads here. Greetings Mathias Buhr -- ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Questions about physic engines.
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 On 2010-02-08 20:23, Ricardo Ruiz wrote: Thanks. Just one question, OSG renders at the maximun amount of FPS it can, but ODE requires a fixed time step. How do you solve this problem? Thanks a lot. Easy, you measure the elapsed time between the frames and execute as many fixed steps as needed to fit inbetween the two frames. I believe that ODE even provides a convenience method for it. Of course, that assumes that the fixed step is small - which is what you want anyway for stability and accuracy. Regards, Jan -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iD8DBQFLcq92n11XseNj94gRAvX6AKC0Mut5cgm61FkXd4hd+wTVi/EjjACfepn+ UXGzcJiBRzsKdCQ7VyPra30= =tdzi -END PGP SIGNATURE- ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Questions about physic engines.
Thanks. Just one question, OSG renders at the maximun amount of FPS it can, but ODE requires a fixed time step. How do you solve this problem? Thanks a lot. -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=23813#23813 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Questions about physic engines.
Hi, I know Paul did some work to use bullet physic engine with osg. A search of osgBullet should point to his work. Cheers, Cedric -- Provide OpenGL services around OpenSceneGraph and more +33 659 598 614 Cedric Pinson mailto:cedric.pin...@plopbyte.net http://www.plopbyte.net On Mon, 2010-02-08 at 19:23 +, Ricardo Ruiz wrote: Thanks. Just one question, OSG renders at the maximun amount of FPS it can, but ODE requires a fixed time step. How do you solve this problem? Thanks a lot. -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=23813#23813 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org signature.asc Description: This is a digitally signed message part ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Questions about physic engines.
Ricardo Ruiz wrote: Thanks. Just one question, OSG renders at the maximun amount of FPS it can, but ODE requires a fixed time step. How do you solve this problem? Thanks a lot. Is there a reason you're not synced to vertical swap? If you were to enable that, then OSG would render at the refresh rate of the monitor (unless you have a huge rendering load). Assuming you use the monitor refresh rate as the ODE simulation interval, then the two sample rates would match. End of problem. I'm not sure my Bullet work will help here, as Bullet doesn't require a fixed time interval. You just pass an arbitrary elapsed time interval to stepSimulation and Bullet produces sim results accordingly. osgBullet (at http://osgbullet.googlecode.com) includes a mechanism to share transform data between separate rendering and physics threads, allowing both to run at whichever rate they choose (not to mention take advantage of multicore systems). So if you can't find any way for ODE and OSG to use the same sample rate, then a mechanism like this might help. I seem to recall someone making some changes to osgViewer a while back to control the frame rate. I didn't really follow that change or discussion. Maybe just looking at the source code would be revealing. -Paul ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
Re: [osg-users] Questions about physic engines.
Hi Ricardo, sorry to not go into the details - so just few hints from my friend that is going his project on ODE+OSG. He done the integration like this: - he loads the scene by OSG - he converts the scene geometry to ODE geometry and sends it to ODE by ODE functions - he setups the ODE world - he starts the ODE simulation - each frame, he reads all required transformations from ODE and updates OSG transformations (ODE simulation is applied to OSG scene) Concerning your questions: - sorry, I have no knowledge about osgPhysics - friction, mass, etc. - it is always a little bit tricky to put additional information to the file (3ds, collada) if the format is not designed to carry this information. However, number of formats supports additional text info connected to a scene graph node. Maybe, this will be the way. My friend is setting this information inside his code after loading each particular scene object. It is easy solution for the starting... - simulation steps: yes, you need to do the simulation steps and then render. It sometimes happens that you are doing number of simulation steps per one rendering step. That is not a problem. But sorry, I did not know implementation details. You will need to take a look to doc and tutorials. Sorry, no more knowledge on my side, but hopefully, it helps a little bit, John Ricardo Ruiz wrote: Hi mates. I have several questions regarding about physics engines in OSG. BTW, I'm a OSG beginner. If I want to use ODE, must I add osgPhysics plugin to my OSG? How can I load a scene with physics values? Let's say I'm creating a scene in 3Ds MAX, and I export it to COLLADA (or any other format). Does OSG or osgPhysics read these values (mass, friction...)? And the most important, how can I tell 3Ds MAX that objets have different physic properties? And the last one. Usually physics engines requere a fixed (or almost) time step, ODE is one of them. How should I manage that inside OSG, I mean, after integrating ODE with ODE? Thank you very much for your time and help. Cheers, Ricardo -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=23771#23771 ___ 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
[osg-users] Questions about physic engines.
Hi mates. I have several questions regarding about physics engines in OSG. BTW, I'm a OSG beginner. If I want to use ODE, must I add osgPhysics plugin to my OSG? How can I load a scene with physics values? Let's say I'm creating a scene in 3Ds MAX, and I export it to COLLADA (or any other format). Does OSG or osgPhysics read these values (mass, friction...)? And the most important, how can I tell 3Ds MAX that objets have different physic properties? And the last one. Usually physics engines requere a fixed (or almost) time step, ODE is one of them. How should I manage that inside OSG, I mean, after integrating ODE with ODE? Thank you very much for your time and help. Cheers, Ricardo -- Read this topic online here: http://forum.openscenegraph.org/viewtopic.php?p=23771#23771 ___ osg-users mailing list osg-users@lists.openscenegraph.org http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
