## Search found 41 matches

Mon Aug 06, 2007 2:52 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: 2D Angle Joint Limits (Box2D-Style)
Replies: 4
Views: 3622

### 2D Angle Joint Limits (Box2D-Style)

I have a physics engine that uses the concepts in Box2D at it's core. I'm trying to implement 2D JointLimits. I already implemented an Angle joint that constrains two bodies to remain at some fixed angle. For this I used the equations: difference = (_body2.TotalRotation - _body1.TotalRotation) - tar...
Wed May 30, 2007 7:25 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Physics and Bullet in Develop Magazine (UK)
Replies: 4
Views: 3316
Very cool. And as a bonus, they also mention my engine: Farseer Physics Engine...

Note: to read the full article you can get a free pdf version of the magazine from there site. google it!
Fri May 25, 2007 8:26 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: 2D Rolling Friction for Box2D Based Engine
Replies: 2
Views: 3379
Yes, it was attached to a chassis using a revolute joint. I will mess around with the joint and see if I can smoothing things out.
Fri May 25, 2007 5:30 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: 2D Rolling Friction for Box2D Based Engine
Replies: 2
Views: 3379

### 2D Rolling Friction for Box2D Based Engine

I have a 2D physics engine based closely on Box2D. I use distance grids for collision detection in order to have other arbitrary collision shapes beside boxes. I've noticed when I try to simulate a wheel, the wheel jitters and jumps a lot once it gets moving at even moderate speeds. The collision de...
Wed Mar 07, 2007 5:25 pm
Forum: General Bullet Physics Support and Feedback
Topic: Compiling Box2D with g++
Replies: 5
Views: 3556
When do you think you will be releasing your GDC 07 version? Want to give any hints as to what has changed?
Fri Jan 05, 2007 5:38 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Split Impulses and Joints
Replies: 53
Views: 33954

### @raigen

@raigan2, does the now correct Bender method give you the rigid angle joints you've been aiming for?

Now that you have it working, will you use it over split impulses for angular joints?

Thanks for doing the leg work to compare these methods.
Wed Jan 03, 2007 4:26 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Split Impulses and Joints
Replies: 53
Views: 33954
Sorry, I must have read your first post to fast. I am using Baumgarte for my joints. I do experience the "hyperactivness" occasionally, but I can deal with it enough for what I'm working on. I hope someone has some answers for you on split impulses. It'd be nice to have the option of using stiffer j...
Wed Jan 03, 2007 1:06 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Split Impulses and Joints
Replies: 53
Views: 33954
I've fought with this as well for a while, as you probably noticed from my other posts. I seem to have it to a point where things seem pretty stable. I never see the "blowing" up you mention. Even if I break the joint and let two bodies drift far apart then re-establish the joint, the bodies spring ...
Sun Dec 31, 2006 1:28 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Adding Joint Makes Collison Spongy (Sequential Impulses)
Replies: 3
Views: 3422
This occurs even when the wheels and mass are equal. I suspect this: "Also, make sure your code has joints and contacts in the same iteration loop. This helps them see each other." may be my issue. So, currently I do this (psuedo code): 1. for each joint do PreStep 2. for each joint apply correction...
Sat Dec 30, 2006 11:17 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Adding Joint Makes Collison Spongy (Sequential Impulses)
Replies: 3
Views: 3422

### Adding Joint Makes Collison Spongy (Sequential Impulses)

I'm using sequential impulses for my 2d engine. Most the code is very similar to Erin Cattos sequential impulse paper. I've notice when I add revolute joints between bodies the collision of the connected bodies with other bodies becomes spongy. Example: If I make a car and attach 2 wheels using revo...
Thu Dec 28, 2006 4:08 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Creating Stiff Angular Springs
Replies: 19
Views: 13800
Yes, "allowed penetration" is what I meant. I can see using it with limits. I was just not sure it would be helpful for a constraint that is designed to simply keep two bodies at a fixed angle with no "play" in either direction.
Wed Dec 27, 2006 2:05 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Creating Stiff Angular Springs
Replies: 19
Views: 13800
Interesting. I will try to implement an AnuglarJoint using this and compare them.

@raigan2. In you current implementation for the AngularJoint. Do you use any slop factor? I don't, but was wondering if I should be...
Tue Dec 19, 2006 12:09 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Creating Stiff Angular Springs
Replies: 19
Views: 13800
I got my AngularJoint working... sort of. If I use 10 iterations and set my stepsize to 1/100, it works quite well, but is still just slightly softer than I would like. I know this has been discussed in other posts, but I really haven't seen a solution. Has anyone come up with a way to harden the jo...
Thu Dec 14, 2006 12:54 pm
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Creating Stiff Angular Springs
Replies: 19
Views: 13800
Thanks for the help so far. A couple follow up questions. Is the CFM constant a matrix? In your joint code, you have: . . . Matrix K = K1 + K2 + K3; For the CFM, should I just add a K4, where K4 is a matrix with each elment set to a constant? Also, I've been digesting other posts on this topic in or...
Thu Dec 14, 2006 2:29 am
Forum: Research and development discussion about Collision Detection and Physics Simulation
Topic: Creating Stiff Angular Springs
Replies: 19
Views: 13800
Looking at the joint code from Box2D. Are the relaxation and ".1" from here bias = -.1 * inverseDt * difference; and here accumulatedImpulse *= relaxation; analogouse in any way to the erp and cfm in ode? I've read the docs from ode, now I'm trying to figure out how to go about implementing a Joint ...