## 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: 5300

### 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: 5300

### 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 climb happ...
Thu Dec 17, 2015 12:07 pm
Forum: General Bullet Physics Support and Feedback
Topic: Modelling a gyroscope in Bullet
Replies: 7
Views: 5300

### 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: 2357

### 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 "force" in...
Tue Dec 15, 2015 2:24 am
Forum: General Bullet Physics Support and Feedback
Topic: simple bullet questions
Replies: 10
Views: 6590

### 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: 1349

### 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: 1848

### Re: Simple Terrain Collision Demo

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: 1887

### 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: 2490

### 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: 2490

### 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
Tue Nov 24, 2015 4:58 pm
Forum: General Bullet Physics Support and Feedback
Topic: Server reconciliation with Bullet?
Replies: 3
Views: 2143

### 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: 2143

### 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: 1807

### 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
Replies: 1
Views: 1549