BK.Physics 物理引擎

BK.Physics 通过为刚性物体赋予真实的物理属性的方式来计算运动、旋转和碰撞反映。

通过 BK.Physics 模拟重力使星星下落：

var space = new BK.Physics.Space({"x":0,"y":-100}, 5)
BK.Director.attachSpace(space)
var screenScale = BK.Director.screenScale;
var tris = [{x: -20 * screenScale, y: -20 * screenScale}, {x: 0, y: 15 * screenScale}, {x: 20 * screenScale, y: -20 * screenScale}];
var staticBody = space.staticBody;
for (var i = 0; i < 9; i++) {
    for (var j = 0; j < 6; j++) {
        var stagger = (j % 2) * 40;
        var offset = {x: (i * 80 + stagger) * screenScale, y: (j * 100 - 50) * screenScale};
        var shape = new BK.Physics.PolygonShape(staticBody, tris, {a:1, b:0, c:0, d:1, tx: offset.x, ty: offset.y}, 0);
        space.addShape(shape);
        shape.friction = 1.0;
        shape.elasticity = 1.0;
    }
}
var verts = new Array(5);
var minX = 10000, maxX = 0, minY = 10000, maxY = 0;
for (var i = 0; i < 5; i++) {
    var angle = -2.0 * 3.1415926 * i / 5;
    verts[i] = {x: 10 * Math.cos(angle) * screenScale, y: 10 * Math.sin(angle) * screenScale};
    if (minX > verts[i].x)
        minX = verts[i].x;
    if (minY > verts[i].y)
        minY = verts[i].y;
    if (maxX < verts[i].x)
        maxX = verts[i].x;
    if (maxY < verts[i].y)
        maxY = verts[i].y;
}
for (var i = 0; i < 100; i++) {
    var mass = 10;
    var moment = BK.Physics.momentForPolygon(mass, verts, {x:0,y:0}, 0);
    var body = new BK.Physics.Body(0, mass, moment, {"x":0,"y":0});
    var x = Math.random() * BK.Director.screenPixelSize.width;
    body.position = {x: x, y: BK.Director.screenPixelSize.height, z: 0};
    space.addBody(body);
    var shape = new BK.Physics.PolygonShape(body, verts, {a:1,b:0,c:0,d:1,tx:0,ty:0}, 0);
    shape.friction = 0.4;
    shape.elasticity = 0;
    space.addShape(shape);
    var centroid = body.centerOfGravity;
    var backTex = new BK.Texture('GameRes://resource/texture/star.png');
    var sp = new BK.Sprite(maxX - minX, maxY - minY, backTex,0,1,1,1);
    sp.anchor = {x: 0.5, y: 0.5};
    sp.attachComponent(body);
    sp.position = {x: x, y: BK.Director.screenPixelSize.height - 100, z: 0};
    BK.Director.root.addChild(sp);
}
//打开测试包围盒
BK.Physics.setSwitch(true);

接口说明：BK.Physics 物理引擎

示例代码：script/demo/physics/physics_demo.js

原文: https://hudong.qq.com/docs/engine/engine/native/func/funcs/physics.html