[BEHAVIOR] Chipmunk Physics

How can I handle collisions between fast moving objects, like the Bullet yes/no in the official physics behavior?

How can I handle collisions between fast moving objects, like the Bullet yes/no in the official physics behavior?

Giganten Use Chipmunks physics on the bullet object (there's no need for you to use bullet behaviour I think, the chipmunk should suffice).

Giganten

The chipmunk physics library doesn't support that. If you want it for something like bullets then ray casting might work for you.

okay, was trying to use it for fast moving balls, like a pinball game.

How would one go about creating a button/switch tile in chipmunk physics that is pushed down when another physics object is on it and lifts back up after other object is not on it anymore? Do I need to set up some kind of joint for it to bounce back up or what would be the best approach?

Giganten

I've found that as long as physics shapes are fired & deflected using forces or impulses the collisions are ok (for realistically high speeds, I haven't tried super fast). It's only when you set velocity manually that things start intersecting a lot, so avoid that if you can.

Waltuo

This is how I'm doing buttons in a platformer where they're triggered by physics. No chipmunk on the button, just overlap testing:

https://dl.dropboxusercontent.com/u/523 ... events.png

R0J0hound

Any idea how to set phase for these gear joints? I've tried signed angle difference & that doesn't work:

https://dl.dropboxusercontent.com/u/523 ... rtest.capx

mattb

The way I look at it the angles of the two gears are related like this:

gearB.angle = (gearA.angle-gearA.initialAngle)*ratio + gearB.initialAngle

So when gearA.angle is zero gearB.angle is:

= -gear.InitialAngle*ratio + gearB.initialAngle

Make that negative and we get the phase:

phase = gear.initialAngle*ratio-gearB.initialAngle

Ok, to simplify the angle calculations make sure the angle of every gear is between 0 and 180 degrees. Then using the following makes rotations spot on in your capx:

phase = -gear.Angle+fGear.n/Gear.n*-fgear.Angle

I'd never have got that, thanks <img src="{SMILIES_PATH}/icon_e_biggrin.gif" alt=":D" title="Very Happy">

Here's the fixed capx in case anyone's interested: https://dl.dropboxusercontent.com/u/523 ... test2.capx

mattb thanks for sharing, it's appreciated!

Got a strange issue that I can't figure out. I'm doing a reflected lasers thing which works when the reflectors have circle collision shapes, but not box or segment.

Here's some screencaps to show the problem. First the circle colls which work as expected:

https://dl.dropboxusercontent.com/u/523 ... Colls.webm

Now box colls:

https://dl.dropboxusercontent.com/u/523 ... Colls.webm

This is the event sheet. A pool of laser & hit sprites are created on start, then every tick they're moved offscreen before some recursive raycasting happens:

https://dl.dropboxusercontent.com/u/523 ... roblem.png

R0J0hound (& anyone else)

Here's a capx of the problem mentioned above. I can't see why this doesn't work, maybe it's something chipmunk-specific that i'm missing?

https://dl.dropboxusercontent.com/u/523 ... nTest.capx

mattb , The next laser is getting caught on the edge of the square(you can see there are more than one contact object on the edge when no laser reflects)..

here's the fix:

Thanks! That does help, which is strange because I also tried excluding the last hit object from the Laser function & that did nothing.

It's still not working fully though. Check this screenshot, there should be 10 segments showing but only 7 are made (this is with hitX/Y moved out 10 pixels):

https://dl.dropboxusercontent.com/u/523 ... erfail.png

mattb , increase the raylength. The ray checked its complete length of 1000, and there weren't any collisions so it made no reflections. Use a higher raylength and it'll work.