tag:blogger.com,1999:blog-7776021459998532494.post5491125285143109348..comments2024-02-19T20:45:17.668-08:00Comments on The Little Engineer That Could: OpenDE and BulletBramhttp://www.blogger.com/profile/07666511303597120943noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-7776021459998532494.post-39514145845180095882013-11-29T09:40:34.451-08:002013-11-29T09:40:34.451-08:00Hi Bram, thanks for sharing.
As Bullet author, I...Hi Bram, thanks for sharing. <br /><br />As Bullet author, I like to improve the library to help users. There is some work-in-progress that will hopefully address your concerns:<br /><br />0) The Bullet 2.x default constraint solver is the same as the OpenDE quickstep solver, but has several improvements. So if you use quickstep, the transition should be smooth. The OpenDE 'worldstep' Dantzig solver is also in Bullet 2.82.<br /><br />1) Bullet 2.82 has Featherstone articulated bodies. Although new and experimental, they can become useful for vehicles, tanks and ragdolls. It also helps the mass ration issue for bodies within the same multi-body.<br /><br />2) Bullet 2.x trunk has improved (MLCP) constraint solvers that address the mass ratio issue. The NNCG solver, based on PGS/SI, like OpenDE quickstep, is promising, it has better convergence which helps mass ratio support. There is also a Lemke solver work-in-progress, but it is currently even slower than Dantzig (OpenDE worldstep)<br /><br />3) Bullet 3.x will get a C API<br /><br />4) Bullet 3.x OpenCL is not useful in gaming at the moment, but its parallel/AoS optimization will help the upcoming CPU version<br /><br />Thanks for helping the Bullet project with feedback,<br />Erwin<br />Erwinhttps://www.blogger.com/profile/09056479728093157309noreply@blogger.comtag:blogger.com,1999:blog-7776021459998532494.post-86335977451100381372013-11-29T06:51:26.860-08:002013-11-29T06:51:26.860-08:00I thought the Mass ratio thing was inherent to all...I thought the Mass ratio thing was inherent to all solvers, about precision error accumulation, and all, and float/double imprecision weren't helping there, as simulation equation imprecisions cannot counter its bad effects. But It's 2-3 yrs without doing physics coding some it's from memory... You could try to revive that old thread http://www.bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=4&t=650&hilit=Mass+Ratio and check if anything new solved that.<br /><br />Love the midi physical knob idea, steampunk retro style tweaking, would make it really nice and fun. <br />Note that you could also hookup a http server https://code.google.com/p/mongoose/ and drive that from a web broswser (some code around about debug visu for that here http://www.altdevblogaday.com/2011/05/03/my-browser-draws-better-than-i-do/)<br />And there, in the web interface, you could put knobs https://github.com/g200kg/webaudio-controls ;) <br />kuraneshttps://www.blogger.com/profile/12641298182065785055noreply@blogger.comtag:blogger.com,1999:blog-7776021459998532494.post-28434373890201005782013-11-28T10:19:46.308-08:002013-11-28T10:19:46.308-08:00Thanks Tuan, for all the pointers, here and on bul...Thanks Tuan, for all the pointers, here and on bullet forum.<br /><br />I'm not sure the mass-ratio is strictly a FP precision thing.<br />If it was, then using doubles instead of floats would solve it.<br /><br />Yeah, I never made my sims tuneable on the fly, but I did fantasize about hooking up a MIDI device for real time tweaks. Can you imagine turning a knob on this to change tyre/road friction, e.g.? http://images.junostatic.com/full/IS396005-01-02-BIG.jpg<br />Never got around to doing this, but I should.Bramhttps://www.blogger.com/profile/07666511303597120943noreply@blogger.comtag:blogger.com,1999:blog-7776021459998532494.post-34509712455153773972013-11-28T01:35:23.745-08:002013-11-28T01:35:23.745-08:00- large mass ratio: would guess that's the cas...- large mass ratio: would guess that's the case for all phys engine (being a floating point inaccurracy thing )<br /><br />- Endless tuning: no easy way out... Note that bullet debugging is very slick, once you implemented the "debugDrawer" interface and that you can use/test blender bullet edition capabilities as well as https://code.google.com/p/bullet-physics-editor/. Best would be having https://developer.nvidia.com/physx-visual-debugger which is a real life saver, especially on mobile.kuraneshttps://www.blogger.com/profile/12641298182065785055noreply@blogger.com