Search found 463 matches
- Wed Dec 23, 2015 10:40 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Modelling a gyroscope in Bullet
- Replies: 7
- Views: 11358
Re: Modelling a gyroscope in Bullet
I don't have the SDK here to check the details, but don't use BT_ENABLE_GYROSCOPIC_FORCE_EXPLICIT as this will require a very small timestep to be accurate - use one of the implicit options. Implicit gyroscopic is actually new to the 2.84 builds, I didn't even realize the system had changed until a...
- Fri Dec 18, 2015 1:22 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Modelling a gyroscope in Bullet
- Replies: 7
- Views: 11358
Re: Modelling a gyroscope in Bullet
Are you simulating it with time steps on the order of 1000Hz or better? 20000RPM certainly isn't in the "low" angular velocity category (so it won't fall down except in very special cases), but it's also well above what bullet can handle in it's default parameters. I can certainly see the ...
- Thu Dec 17, 2015 12:07 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Modelling a gyroscope in Bullet
- Replies: 7
- Views: 11358
Re: Modelling a gyroscope in Bullet
By falling do you mean rotating "down" so that +z oriented object is now oriented -y? If so, that sounds correct for "low" angular velocity, with the object precession occurring about -y. Simply making gravity be on the -z axis should make it work as you want.
- Thu Dec 17, 2015 12:02 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Circular motion
- Replies: 3
- Views: 5045
Re: Circular motion
There is no balancing force. Force = mass * acceleration ---> acceleration = Force / mass The force acts and there is a resulting non-zero acceleration toward the center of the circle. There's definitely no "balancing" force since the object changes acceleration but there is a countering ...
- Tue Dec 15, 2015 2:24 am
- Forum: General Bullet Physics Support and Feedback
- Topic: simple bullet questions
- Replies: 10
- Views: 13135
Re: simple bullet questions
There's an old fracture demo at https://code.google.com/p/bullet/source ... actureDemo , did you get a chance to study it to see differences in approach?
- Mon Dec 14, 2015 10:58 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Absolute position of a hinge
- Replies: 1
- Views: 3120
Re: Absolute position of a hinge
You can get the position in respect to one of the bodies, the absolute position of the body, and then just multiply the transforms to get both position and initial orientation. Not too difficult or time consuming. If you multiply again by the rotation, you can get that too if you need it later.
- Sat Dec 12, 2015 2:15 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Simple Terrain Collision Demo
- Replies: 2
- Views: 4006
Re: Simple Terrain Collision Demo
https://code.google.com/p/bullet/source ... nk%2FDemos
You can still access the old demos just fine. Remember that future updates to Bullet might break certain functionality though
You can still access the old demos just fine. Remember that future updates to Bullet might break certain functionality though
- Fri Dec 04, 2015 2:29 am
- Forum: General Bullet Physics Support and Feedback
- Topic: ground/soil simulation
- Replies: 2
- Views: 4197
Re: ground/soil simulation
Doesn't look like there's actually any simulation going on, rather just feature subtraction based on collision depth. One way of doing it: Basically all you need to do is turn off standard collision and then calculate the intersect area. Remove nodes of the triangle mesh and add new ones around the ...
- Tue Dec 01, 2015 5:53 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Joint constraint specs
- Replies: 3
- Views: 5570
Re: Joint constraint specs
Oh ok! Thanks for your help. My setups are now working properly. I also found out that it is sometimes good for the stability of a joint to add -EPS, EPS as the joint limits when I basically need a zero limit (EPS: epsilon being a very small non-zero value). That's usually not the best idea, since ...
- Mon Nov 30, 2015 4:20 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Joint constraint specs
- Replies: 3
- Views: 5570
Re: Joint constraint specs
http://ode-wiki.org/wiki/index.php?titl ... _Functions is a good place to start
For the purposes of constraint types,
odehinge = bthinge~=mb hinge
btpoint2point~=mb ball~=bt6dof==ode ball and socket
For the purposes of constraint types,
odehinge = bthinge~=mb hinge
btpoint2point~=mb ball~=bt6dof==ode ball and socket
- Tue Nov 24, 2015 4:58 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Server reconciliation with Bullet?
- Replies: 3
- Views: 5051
Re: Server reconciliation with Bullet?
Because then I would have to call stepSimulation which would affect other things in my simulation. That's the point of rigid body dynamics, why try to fight it? From what you are describing, you'll have an inconsistent simulation step when you do take it, especially if the characters collide with a...
- Tue Nov 24, 2015 12:09 pm
- Forum: General Bullet Physics Support and Feedback
- Topic: Server reconciliation with Bullet?
- Replies: 3
- Views: 5051
Re: Server reconciliation with Bullet?
Why not just compute the effective velocity (after aggregating all inputs) and pass that to the server side sim?
- Fri Nov 20, 2015 2:04 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Calculating the minimum force needed to pick up an object
- Replies: 1
- Views: 3778
Re: Calculating the minimum force needed to pick up an objec
The minimum force required is F=Ma, where M is the mass of the object and a is the total acceleration including gravity. No need for bullet. If you are using friction only (not a good approximation if you have non-smooth small objects and a human like gripper), the normal force (gripping force) is j...
- Thu Nov 05, 2015 6:05 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Arcade racing physics
- Replies: 1
- Views: 3362
Re: Arcade racing physics
Check the vehicle examples in the download code. There's a few other examples like raycast vehicles that might help too. As for the control at high speed, same goes for old cars actually. Newer cars sometimes have velocity dependent steering, which means you need to turn the wheel more for the same ...
- Thu Nov 05, 2015 5:59 am
- Forum: General Bullet Physics Support and Feedback
- Topic: Physical accuracy of a simulation using bullet physics.
- Replies: 2
- Views: 4291
Re: Physical accuracy of a simulation using bullet physics.
Rope is one of those softbody problems that doesn't really play nicely with rigid body physics. If you only care about the statics or have a heavy rope (frequencies produced by the simple wave equation for the length of the rope are much smaller than the sampling time of your simulation), you will g...