Search found 84 matches
- Fri May 13, 2011 8:37 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Set friction doesn't change anything.
- Replies: 4
- Views: 12590
Re: Set friction doesn't change anything.
The behaviour of rigid bodies _should_ be independent of the overall mass scaling (so if you multiply the masses of all objects by some constant, it shouldn't change the behaviour). Physics engines will probably not be that perfect, but I would have thought would be OK for what you describe (can't b...
- Thu May 12, 2011 1:13 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Box on an inclined plane... friction?
- Replies: 2
- Views: 4683
Re: Box on an inclined plane... friction?
I have a box on an plane. The plane is inclined by an angle phi. The friction parameter "mu" is set to 0.35 on both of them. Normally the friction coefficient in physics engines is calculated either by a lookup table, or by multiplying a friction parameter on each surface. So, assuming th...
- Thu Sep 23, 2010 10:36 am
- Forum: Applications, Games, Demos or Movies using Bullet
- Topic: studioNEST Momentum
- Replies: 2
- Views: 6706
Re: studioNEST Momentum
Looks like a great integration to me! Hope lots of people find it useful.
- Thu Aug 12, 2010 10:34 am
- Forum: Links, Papers, Libraries, Demos, Movies, Comparisons
- Topic: TriplVing's Bullet Vs PhysX Vs ODE performance comparison
- Replies: 12
- Views: 25344
Re: Bullet Vs PhysX Vs ODE Restitution question
I'm not sure that this is a very fair performance test for the engines! Engines will be optimised for more than one body, and also probably for bodies in contact rather than unconstrained. For example, when I run the PhysX test case I get timings of around 0.07ms, for one sphere falling. However, th...
- Thu Apr 22, 2010 9:02 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Low Torque on edge
- Replies: 9
- Views: 6885
Re: Low Torque on edge
I set gravity 20 instead of 10. Slightly better but still not realistic. If you want to do a direct comparison with your cell phone then you would need to set gravity to around 500. This should result in relative motions being the same (i.e. the same amount of world time to rotate one revolution, o...
- Tue Mar 16, 2010 10:14 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Simple newtonian simulations giving wrong results
- Replies: 4
- Views: 5024
Re: Simple newtonian simulations giving wrong results
Most physics engines optionally add some simple damping to aid stability. I've not checked, but it may be that Bullet has this non-zero by default.
- Fri Jul 31, 2009 2:29 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: strange capsule behaviour
- Replies: 13
- Views: 9702
Re: strange capsule behaviour
It's behaving like this because when a capsule is rolling on its end like in your video, it spins much faster than a cylinder would for the same linear velocity, so it behaves strongly as a gyroscope. Rather than the non-contacting end falling down, the capsule rolls in a circle (to the left in your...
- Tue Jul 28, 2009 12:06 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Jumpy kinematic->dynamic collisions at small timesteps
- Replies: 17
- Views: 19223
Re: Jumpy kinematic->dynamic collisions at small timesteps
This is a stab in the dark, since I don't use Bullet... but if the solver is aiming to eliminate the penetration error (or some fraction of it) over a fixed number of updates using Baumgarte stabilisation, then a very small timestep will result in large error-correcting velocities because they'll be...
- Mon May 18, 2009 10:42 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Doing a 'sphere cast'
- Replies: 7
- Views: 8728
Re: Doing a 'sphere cast'
If you don't detect overlap between the sphere and the mesh, you want to check if that's because the sphere centre is completely inside the mesh. If your mesh is closed, then you can tell if a point (i.e. the sphere centre) is inside it by doing a ray test in some arbitrary direction. If the number ...
- Mon May 18, 2009 10:27 am
- Forum: General Bullet Physics Support and Feedback
- Topic: energy spent for joint motor, difficulty 2.73 --> 2.74
- Replies: 5
- Views: 4995
Re: energy spent for joint motor, difficulty 2.73 --> 2.74
Can't help with the Bullet-specific stuff, but
Units of impulse = mass * distance / time
Units of energy = mass * distance^2 / time^2
so your calculation (energy = impulse * impulse) must be wrong anyway...
Units of impulse = mass * distance / time
Units of energy = mass * distance^2 / time^2
so your calculation (energy = impulse * impulse) must be wrong anyway...
- Tue Feb 03, 2009 2:15 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Problems with bullet 2.73, SSE and std::vector
- Replies: 12
- Views: 10134
Re: Problems with bullet 2.73, SSE and std::vector
STLport sounds like a good option, though I somehow doubt that it has the same debugging support in Visual Studio as MS STL has, esp. being able to see the size and any entry in a std::vector. You can customise the way types are displayed in Visual Studio by editing: Common7\Packages\Debugger\autoe...
- Fri Sep 19, 2008 8:55 am
- Forum: Applications, Games, Demos or Movies using Bullet
- Topic: Natural Motion
- Replies: 9
- Views: 15473
Re: Natural Motion
Same error as before...
- Fri Aug 22, 2008 9:04 am
- Forum: General Bullet Physics Support and Feedback
- Topic: why Bullet demos feel like happening on the moon?
- Replies: 16
- Views: 18536
Re: why Bullet demos feel like happening on the moon?
i disagree passionately, i mean, if its not VERY, VERY obvious what "visual errors" im talking about then i must assume something is wrong with my computer... 1. It is possible that your computer returns weird timing results (I saw this very occasionally a while back with one or two peopl...
- Tue Jul 08, 2008 2:22 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Force/Impulse timebase
- Replies: 29
- Views: 46912
Re: Force/Impulse timebase
Other physics SDKs, like Havok and Ageia also clear out the force after the simulation step I think, but I need to verify. Whatever other SDKs do... the idea of clearing the force after each simulation step has never made sense to me for two reasons: 1. The force is quite clearly "owned" ...
- Wed Jun 25, 2008 10:16 am
- Forum: Research and development discussion about Collision Detection and Physics Simulation
- Topic: Flutter and Tumble: The Physics of Falling Paper
- Replies: 6
- Views: 9402
Re: Flutter and Tumble: The Physics of Falling Paper
One of the soft body demos in Bullet already simulates this, and it's pretty cool.