Rotating a polygon around it's center

[scofield-ua]

I have a problem. Is it possible to rotate polygon around it's center using Polygon class functions?

I'm trying to use rotate function, but it's return not what I expected.

Here is how my polygon looks by default:

After rotate(1):

[jriecken]

How are you constructing the Polygon - do you have some example code?

The rotate method rotates using the pos of the Polygon as the origin of rotation (also it takes in the angle in radians, not degrees)

So if you use the pos as the center of the polygon and then define the points around/relative to that position it will rotate around that.

[scofield-ua]

How are you constructing the Polygon - do you have some example code?

Sure, here is example code:

var P = SAT.Polygon; 
var V = SAT.Vector;
var points = [];

var angle = 0.05;
var r = 64;
while (angle < 2 * Math.PI / 2) {
    var x = r * -Math.cos(angle);
    var y = r * -Math.sin(angle);

    points.push(new V(x, y));

    angle += 0.5;
}

var polygon = new P(new V(100, 100), points);

Sorry about stupid question, I'm probably just don't understand something.

[jriecken]

Hm, that seems to work for me - take a look at this JSFiddle: https://jsfiddle.net/1d67zsaw/

I copied your code, drew the polygon, rotated it, and drew it again - it rotates around the center of the half-circle.

[scofield-ua]

Yeah. Thanks man. Seems like odd behavior from engine polygon draw method.

Nice library.