## Search found 463 matches

Fri Feb 12, 2016 12:37 pm
Forum: General Bullet Physics Support and Feedback
Topic: Imitation sensor field of view.
Replies: 3
Views: 2710

### Re: Imitation sensor field of view.

Well, ultrasound sensors have a maximum range, so you could try making a ghost object in the shape of a cone up to that maximum range. The collision manifold should give you a reasonable approximation of flat surfaces (after applying some sort of min-filter), and should tell you if it's in contact w...
Thu Feb 04, 2016 6:15 am
Forum: General Bullet Physics Support and Feedback
Topic: Rag-Doll Constraint Problem
Replies: 3
Views: 3337

### Re: Rag-Doll Constraint Problem

Try checking out the ODE manual (instead of bullet), they explain what a/b transforms are and how the constraints work. It's a bit stiffer reading than bullet's manual, but it can help bring you up to speed on general simulation terminology
Mon Feb 01, 2016 1:50 am
Forum: General Bullet Physics Support and Feedback
Topic: Automatic interpolation of movement
Replies: 1
Views: 1714

### Re: Automatic interpolation of movement

If you check the code for btDiscreteDynamicsWorld, you'll see it internally uses motion states to do the interpolation
Sat Jan 23, 2016 1:10 am
Forum: General Bullet Physics Support and Feedback
Topic: General questions for a thesis work
Replies: 2
Views: 2307

### Re: General questions for a thesis work

For deformable body simulation in surgery applications, bullet is not something that would be recommended. You'll need a more accurate/robust method (usually ansys+opentissue) and a hell of a lot of computing power. http://scc.ist.hokudai.ac.jp/publications/publications-e.html has a few publications...
Wed Jan 20, 2016 10:26 am
Forum: General Bullet Physics Support and Feedback
Topic: How to specify slider constraint axis
Replies: 7
Views: 3864

### Re: How to specify slider constraint axis

I understand how you can set an offset but what I still don't quite understand is how you specify the axis. In your post you mention the Z axis, but how did you set that. If say you wanted the X or Y axis for your slider, how would you specify those, or an arbitrary axis, which is what I'm interest...
Wed Jan 20, 2016 4:47 am
Forum: General Bullet Physics Support and Feedback
Topic: How to specify slider constraint axis
Replies: 7
Views: 3864

### Re: How to specify slider constraint axis

frames are basically just definitions of the transformation axis in the local coordinates of the bodies that make up that joint. For example, you have translation across the z axis for a pair of squares of length 1 starting with the two bodies perfectly stacked along the world z axis. The resulting ...
Thu Jan 14, 2016 1:24 am
Forum: General Bullet Physics Support and Feedback
Topic: What one should do when simulation explodes?
Replies: 8
Views: 3551

### Re: What one should do when simulation explodes?

- "some constraint is using infinite impulse rather than fixed bounds" -> how do I check for that, I could not find a field/function to set max impulse response, maybe if we user motorized constraints it would be max force applied? Motor constraints would certainly give you control, as would breaki...
Wed Jan 13, 2016 4:55 am
Forum: General Bullet Physics Support and Feedback
Topic: What one should do when simulation explodes?
Replies: 8
Views: 3551

### Re: What one should do when simulation explodes?

In general, these are the steps you should use to solve it: 1) Check for programming errors. Perhaps one body is randomly very far from where it should be (relatively), or some constraint is using infinite impulse rather than fixed bounds 2) Increase simulation frequency, but keep ERP in mind. Use m...
Sun Jan 10, 2016 5:16 pm
Forum: General Bullet Physics Support and Feedback
Topic: Scaling the world including forces?
Replies: 5
Views: 2611

### Re: Scaling the world including forces?

Higher simulation frequency normally helps the most, after that switching solvers to dantzig or similar and using DP
Sat Jan 09, 2016 7:36 am
Forum: General Bullet Physics Support and Feedback
Topic: Lots of newbie questions
Replies: 2
Views: 1747

### Re: Lots of newbie questions

If you're dealing with planets and real gravity, you'll need true n-body physics. There are a few physics solvers out there, but you'll likely have to make you own custom system that mixes rigid body and n-body particle physics together. You'll find bullet works well alone at high frequency, but if ...
Tue Jan 05, 2016 4:01 am
Forum: General Bullet Physics Support and Feedback
Topic: Solving collisions and constraints, causes unwanted movement
Replies: 3
Views: 2157

### Re: Solving collisions and constraints, causes unwanted move

Thanks for the suggestion! Are these solvers supposed to be interchangeable? Do they all support all the shapes/constraints etc.? When I try to use any other than the standard one, I get an exception somewhere in the step function.. I'll see if I can track down the problem. In the mean time, is the...
Mon Jan 04, 2016 1:17 pm
Forum: General Bullet Physics Support and Feedback
Topic: Friction: what is the unit?
Replies: 5
Views: 4326

### Re: Friction: what is the unit?

OK, but what does this number mean? theoretically speaking max parallel force <= mu (that number) * perpendicular force. If you press down with 0.5N of force and the combined mu is 0.5, the maximum friction force will be 1N. Bullet friction is a bit off the theoretical mark due to approximations, b...
Fri Jan 01, 2016 4:09 am
Forum: General Bullet Physics Support and Feedback
Topic: Simple example of bullet with a GUI + bouncing ball
Replies: 4
Views: 2966

### Re: Simple example of bullet with a GUI + bouncing ball

Just use the default browser, and then change the code in one of the examples so that there is a single ball spawned. You can also look at the older code on the google code section that has fewer fancy things, but even that won't have an example that simple because it's nearly trivial.
Thu Dec 31, 2015 4:03 am
Forum: General Bullet Physics Support and Feedback
Topic: Scaling the world including forces?
Replies: 5
Views: 2611

### Re: Scaling the world including forces?

Gravity should not be affected by time-step size, but motor constraints (and likely any constraint/impulse) are affected by it. Most likely what you are experiencing is just "time dilation" caused by stepping just 1/240 when real world time increases by 1/60. Just use the built in function to automa...
Thu Dec 24, 2015 4:09 am
Forum: General Bullet Physics Support and Feedback
Topic: Rocket Landing
Replies: 2
Views: 1810

### Re: Rocket Landing

This is practically trivial in Bullet thankfully :D Just call "applyForce" on the rigid body you want to be moved and apply a force vector parallel with the direction of the body orientation . If you want vectored thrust you can use the same thing with an offset (second input for that function) set ...