Hi. I've got a problem with a simple collision detection between a box-shaped moving object and the borders of my view, modeled with 4 segmented shapes attached to a static body.

What steps will reproduce the problem? 1. Build a simple shape (a rectangle) and 4 statics segments among which the box can move. The 4 borders are the border of my window 2. Apply some impulse to the shape, so that it bounces off the border a few times (i.e. the topmost..) 3. After a few bounces, the object gains speed and it doesn't bounce off the border anymore, it just passes through it as if the body/shape was not there 4. The behaviour goes away if the segments composing the static body have a big radius (say.. 15, or 20).. the behaviour is almost istantaneous (after the first bounce the collisions disappears) if the radius is 1. If the radius is 5, after a few bounces the collision disappears.

What is the expected output? What do you see instead?

I expect collisions to be still detected and handled.

What version of the product are you using? On what operating system?

Running on IPhone OS 3.1 using Chipmunk 4.1.0

Please provide any additional information below.

Please see full code attached. As far as I know, these are the relevant snippets of the code:

1) setting up of the space

    space = cpSpaceNew();   

// Define a gravity vector    
//inzialmente nullo. La roba non si muove
space->gravity = cpv( 00,  0);       
space->elasticIterations = 10;  

//setup ball and shapes..
// Create our ball's body with 100 mass and infinite moment   
ballBody = cpBodyNew(100.0, INFINITY);   

///..other setup (i.e. rectangular shape) 
ballShape->collision_type = 1; // Collisions are grouped by 

types

// Add the shape to out space    
cpSpaceAddShape(space, ballShape);   

// Create our floor's body and set it's position   
cpBody *floorBody = cpBodyNew(INFINITY, INFINITY);   

floorBody->p = cpvzero; 

// Define our shape's vertexes   
const cpFloat elast=0.4;
const cpFloat friction=0.1;
const int radius=5;
//add 3 other sides
//top
floorShape = cpSegmentShapeNew(floorBody,  cpv(fieldSizeW,416),cpv

(0,416),radius);
floorShape->e = elast; floorShape->u = friction; floorShape- >collision_type = 1;
floorShape->data = floor;
cpSpaceAddStaticShape(space, floorShape);

2) Handle accelerometer movement

float fattoreImpulso=3000*variatore*2;

        cpBodyResetForces(ballBody);
        space->gravity = cpv(0,0);

        cpBodyApplyImpulse(ballBody,cpv(fattoreImpulso* 

accX,-fattoreImpulso* accY),cpvzero); break;

3) test it, make it bounce at the top or bottom, then tilt the device, gain some momentum, make it bounce again.. after a few moments, the collision disappears.

4) I've tried changing collision type (i'm not sure what it is for) to no avail.

I enclose the relevant files, i't s an UIView. Look for the - setupChipmunk (for seting up the physics) - didAccelerate method (movement)

Thank you. Walter Gamba

I also get this problem for fast-travelling objects. From what I noticed, it happens when the object's center penetrates the segment (or other object) where its center point gets on the other side. The object gets warped on the other side and is able to exit the game area.

This can be temporarily solved by using a smaller time step and more iterations, or, as mentioned, increasing the radius of the segments. I know this is an old issue, but it still is affecting the latest svn trunk version.

I'm running chipmunk-physics svn r697 on Linux x64, also tested on Linux x86.