Box2D Forums

I am working on a game using Box 2D and Cocos2D, and have turned off gravity as I am simulating a "table top" type game. I am using linear damping to simulate friction. When I need to have the user move a body, I apply a linear impulse based on how the user swipes. It all works great, except on the rare instances when my impulse x value equals the negative of the impulse y value. For example, based on the user swipes, if they swipe exactly at 135 degrees, the impulse value might equal say (-200,200) or if they swipe exactly at 315 degrees the impulse value might equal (200,-200). When this happens no impulse is applied (body doesn't move, or only moves a little). If I test for these scenarios and add a small offset (like .1) to either x or y value, it works fine. I even overrode the touch sensing calculations, and simply applied the impulse directly to make sure my code wasn't the issue.

I plan to strip more of my code out to further isolate the issue (to make sure something else in my code is not causing an issue)

Has anyone else come across this? (I am using the latest stable version of Cocos2d (1.0.1) with Box2d).

Thanks

If I understand this correctly, you're saying that this has no effect?

body->ApplyLinearImpulse( -200, 200 );

I'm not sure how you could isolate the issue better than that...
Just as a guess, I would suspect a x/y typo somewhere.

Think I got it solved, it was something else in a completely different section of code when I was checking whether or not the body was at rest.

Thanks