esengine/source/src/Physics/Shapes/Box.ts

///<reference path="./Polygon.ts" />
module es {
    /**
     * 多边形的特殊情况。在进行SAT碰撞检查时，我们只需要检查2个轴而不是8个轴
     */
    export class Box extends Polygon {
        public width: number;
        public height: number;

        constructor(width: number, height: number){
            super(Box.buildBox(width, height), true);
            this.width = width;
            this.height = height;
        }

        /**
         * 在一个盒子的形状中建立多边形需要的点的帮助方法
         * @param width
         * @param height
         */
        private static buildBox(width: number, height: number): Vector2[]{
            // 我们在(0,0)的中心周围创建点
            let halfWidth = width / 2;
            let halfHeight = height / 2;
            let verts = new Array(4);
            verts[0] = new Vector2(-halfWidth, -halfHeight);
            verts[1] = new Vector2(halfWidth, -halfHeight);
            verts[2] = new Vector2(halfWidth, halfHeight);
            verts[3] = new Vector2(-halfWidth, halfHeight);

            return verts;
        }

        /**
         * 更新框点，重新计算中心，设置宽度/高度
         * @param width
         * @param height
         */
        public updateBox(width: number, height: number){
            this.width = width;
            this.height = height;

            // 我们在(0,0)的中心周围创建点
            let halfWidth = width / 2;
            let halfHeight = height / 2;

            this.points[0] = new Vector2(-halfWidth, -halfHeight);
            this.points[1] = new Vector2(halfWidth, -halfHeight);
            this.points[2] = new Vector2(halfWidth, halfHeight);
            this.points[3] = new Vector2(-halfWidth, halfHeight);

            for (let i = 0; i < this.points.length; i ++)
                this._originalPoints[i] = this.points[i];
        }

        public overlaps(other: Shape){
            // 特殊情况，这一个高性能方式实现，其他情况则使用polygon方法检测
            if (this.isUnrotated){
                if (other instanceof Box)
                    return this.bounds.intersects(other.bounds);

                if (other instanceof Circle)
                    return Collisions.isRectToCircle(this.bounds, other.position, other.radius);
            }

            return super.overlaps(other);
        }

        public collidesWithShape(other: Shape){
            // 特殊情况，这一个高性能方式实现，其他情况则使用polygon方法检测
            if (other instanceof Box && (other as Box).isUnrotated){
                return ShapeCollisions.boxToBox(this, other);
            }

            // TODO: 让 minkowski 运行于 cricleToBox

            return super.collidesWithShape(other);
        }

        public containsPoint(point: Vector2){
            if (this.isUnrotated)
                return this.bounds.contains(point.x, point.y);

            return super.containsPoint(point);
        }
    }
}