JBox2D collisions not bouncing

Question

I have an Android application using JBox2D for physics simulation. The only dynamic object is a 0.07m radius circle, as well as several static circles and rectangles in a total game area of about 20m by 20m. I'm also using a few custom forces through the ApplyForce method.

Whenever any bodies collide, they do collide correctly however they don't bounce; everything just thuds together. All bodies have their densities, frictions and restitutions set (some objects have a restitution greater than 1).

Does anyone have any ideas why these collisions aren't working? I think it might be because the bodies aren't moving fast enough for JBox2D to count as proper collisions (there is a cutoff in Box2D).

Thanks!

This might be of help `Ball to Ball Collision - Detection and Handling` http://stackoverflow.com/questions/345838/ball-to-ball-collision-detection-and-handling — Mob, Sep 24 '11 at 21:28
what version of the engine are you using? I would recommend trying again with the 2.1.2.2 release, this may have been fixed — Daniel Murphy, Feb 12 '12 at 23:07

score 1 · Answer 1 · edited Apr 26 '12 at 08:04

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setting Settings.velocityThreshold = 0.0001f; (or very small) solved it for me.

edited Apr 26 '12 at 08:04

Sergey Glotov

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answered Apr 26 '12 at 07:23

Heikki

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Is it possible to change this without recompiling JBox2D? I'm using v2.2.1.1 and it's a static final. – afaulconbridge Nov 25 '13 at 17:24

score 0 · Answer 2 · answered Sep 28 '11 at 18:51

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I found a partial solution to this - Box2D (at least JBox2D) ignores restitution if the velocity is below a certain threshold - by scaling all my objects up by a factor of 10, the threshold becomes relatively lower, and objects bounce.

answered Sep 28 '11 at 18:51

neuropie

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JBox2D collisions not bouncing

2 Answers2