esengine/source/src/Math/MathHelper.ts

module es {
    export class MathHelper {
        public static readonly Epsilon: number = 0.00001;
        public static readonly Rad2Deg = 57.29578;
        public static readonly Deg2Rad = 0.0174532924;

        /**
         * 将弧度转换成角度。
         * @param radians 用弧度表示的角
         */
        public static toDegrees(radians: number){
            return radians * 57.295779513082320876798154814105;
        }

        /**
         * 将角度转换为弧度
         * @param degrees
         */
        public static toRadians(degrees: number){
            return degrees * 0.017453292519943295769236907684886;
        }

        /**
         * mapps值(在leftMin - leftMax范围内)到rightMin - rightMax范围内的值
         * @param value
         * @param leftMin
         * @param leftMax
         * @param rightMin
         * @param rightMax
         */
        public static map(value: number, leftMin: number, leftMax: number, rightMin: number, rightMax: number){
            return rightMin + (value - leftMin) * (rightMax - rightMin) / (leftMax - leftMin);
        }

        public static lerp(value1: number, value2: number, amount: number){
            return value1 + (value2 - value1) * amount;
        }

        public static clamp(value: number, min: number, max: number){
            if (value < min)
                return min;

            if (value > max)
                return max;

            return value;
        }

        public static pointOnCirlce(circleCenter: Vector2, radius: number, angleInDegrees: number){
            let radians = MathHelper.toRadians(angleInDegrees);
            return new Vector2(Math.cos(radians) * radians + circleCenter.x, Math.sin(radians) * radians + circleCenter.y);
        }

        /**
         * 如果值为偶数，返回true
         * @param value
         */
        public static isEven(value: number){
            return value % 2 == 0;
        }

        /**
         * 数值限定在0-1之间
         * @param value
         */
        public static clamp01(value: number){
            if (value < 0)
                return 0;

            if (value > 1)
                return 1;

            return value;
        }

        public static angleBetweenVectors(from: Vector2, to: Vector2){
            return Math.atan2(to.y - from.y, to.x - from.x);
        }
    }
}