esengine/source/src/Utils/Vector2Ext.ts

module es {
    export class Vector2Ext {
        /**
         * 检查三角形是CCW还是CW
         * @param a
         * @param center
         * @param c
         */
        public static isTriangleCCW(a: Vector2, center: Vector2, c: Vector2) {
            return this.cross(Vector2.subtract(center, a), Vector2.subtract(c, center)) < 0;
        }

        /**
         * 计算二维伪叉乘点(Perp(u)， v)
         * @param u
         * @param v
         */
        public static cross(u: Vector2, v: Vector2) {
            return u.y * v.x - u.x * v.y;
        }

        /**
         * 返回与传入向量垂直的向量
         * @param first
         * @param second
         */
        public static perpendicular(first: Vector2, second: Vector2) {
            return new Vector2(-1 * (second.y - first.y), second.x - first.x);
        }

        /**
         * Vector2的临时解决方案
         * 标准化把向量弄乱了
         * @param vec
         */
        public static normalize(vec: Vector2) {
            let magnitude = Math.sqrt((vec.x * vec.x) + (vec.y * vec.y));
            if (magnitude > MathHelper.Epsilon) {
                vec = Vector2.divide(vec, new Vector2(magnitude));
            } else {
                vec.x = vec.y = 0;
            }

            return vec;
        }

        /**
         * 通过指定的矩阵对Vector2的数组中的向量应用变换，并将结果放置在另一个数组中。
         * @param sourceArray
         * @param sourceIndex
         * @param matrix
         * @param destinationArray
         * @param destinationIndex
         * @param length
         */
        public static transformA(sourceArray: Vector2[], sourceIndex: number, matrix: Matrix2D,
                                 destinationArray: Vector2[], destinationIndex: number, length: number) {
            for (let i = 0; i < length; i ++){
                let position = sourceArray[sourceIndex + i];
                let destination = destinationArray[destinationIndex + i];
                destination.x = (position.x * matrix.m11) + (position.y * matrix.m21) + matrix.m31;
                destination.y = (position.x * matrix.m12) + (position.y * matrix.m22) + matrix.m32;
                destinationArray[destinationIndex + i] = destination;
            }
        }

        public static transformR(position: Vector2, matrix: Matrix2D){
            let x = (position.x * matrix.m11) + (position.y * matrix.m21) + matrix.m31;
            let y = (position.x * matrix.m12) + (position.y * matrix.m22) + matrix.m32;
            return new Vector2(x, y);
        }

        /**
         * 通过指定的矩阵对Vector2的数组中的所有向量应用变换，并将结果放到另一个数组中。
         * @param sourceArray
         * @param matrix
         * @param destinationArray
         */
        public static transform(sourceArray: Vector2[], matrix: Matrix2D, destinationArray: Vector2[]) {
            this.transformA(sourceArray, 0, matrix, destinationArray, 0, sourceArray.length);
        }

        public static round(vec: Vector2){
            return new Vector2(Math.round(vec.x), Math.round(vec.y));
        }
    }
}