## Problem with static poly

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Brain21
Posts: 3
Joined: Tue Dec 23, 2008 9:30 am
Contact:

### Problem with static poly

Hi, I'm trying out Chipmunk and I have a problem. What I've done so far is to create a ground (static segment) and a ball. Then I added a rectangle (poly) and hope to make it static. It is static in the scene, but the ball goes right through it. I have the ground at the bottom of the screen and the ball at the top and the rectangle between the two and I make gravity down 10.0. The ball falls and stops at the ground, but goes through the rectangle. When I change the rectagle poly to a segment, it all works fine. Here's the code I'm using for the rectangle:

Code: Select all

``````void CreateRect( float x1, float y1, float x2, float y2 )
{
int num = 4;
float px, py, dx, dy;

cpBody *bod;
cpShape *shp;

px = ( x1 + x2 ) / 2.0;
py = ( y1 + y2 ) / 2.0;
dx = ( x2 - x1 ) / 2.0f;
dy = ( y2 - y1 ) / 2.0f;

cpVect verts[] = {
cpv(-dx,-dy),
cpv(dx, -dy),
cpv( dx, dy),
cpv( -dx, dy),
};

bod = cpBodyNew(INFINITY, INFINITY);
cpVect offset = cpv( px, py );
shp = cpSegmentShapeNew(bod, cpv(x1, y1), cpv( x2, y1), 0 );  //This works
//	shp = cpPolyShapeNew(bod, num, verts, offset );                      //This doesn't
shp->e = 1.0; shp->u = 1.0;
}
``````
So the line that's commented out is the one that does not work (ball passes through).
Any ideas?

Denis.
sickman
Posts: 19
Joined: Mon Oct 06, 2008 7:50 am
Contact:

### Re: Problem with static poly

The points of polygon must be given in counter-clockwise order.

Code: Select all

``````cpVect verts[] = {
cpv(-dx,-dy),
cpv(dx, -dy),
cpv( dx, dy),
cpv( -dx, dy)
};
``````
It should go

Code: Select all

``````cpVect verts[] = {
cpv(-dx, -dy ),
cpv(-dx, dy ),
cpv(dx, dy ),
cpv(dx, -dy)
};
``````
Brain21
Posts: 3
Joined: Tue Dec 23, 2008 9:30 am
Contact:

### Re: Problem with static poly

Thanks! I had missed that part in the documents. It works now.

Brain21
sickman
Posts: 19
Joined: Mon Oct 06, 2008 7:50 am
Contact:

### Re: Problem with static poly

That thing should be highlighted in red and underlined in manual because everybody seems to stumble on it, unless it hasn't already.

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