feat(math): add math libs (Orillusion#15)

Add random numbers
Add ray detection
Add Triangle, Rect, UV, TimeInterpolator
Add Vector2, Vector3, Vector4

src/engine/math/Rand.ts

@@ -0,0 +1,97 @@
+import { getFloatFromInt } from './MathUtil';
+
+/**
+ * 'Rand' is a random number generator based on an improved xorshift algorithm, 
+ * which is a modification of the Linear Congruential Generator (LCG) method.
+ * @group Math
+ */
+export class Rand {
+    private _x: number = 0;
+    private _y: number = 0;
+    private _z: number = 0;
+    private _w: number = 0;
+
+    /**
+     * Create a random number generator object with a specified seed.
+     * @param seed Random seed
+     */
+    constructor(seed = 0) {
+        this.seed = seed;
+    }
+
+    /**
+     * Random seed
+     */
+    public get seed(): number {
+        return this._x;
+    }
+
+    public set seed(value: number) {
+        this._x = value;
+        this._y = this._x * 1812433253 + 1;
+        this._z = this._y * 1812433253 + 1;
+        this._w = this._z * 1812433253 + 1;
+    }
+
+    /**
+     * Convert an integer to a floating-point number
+     * @param value integer
+     * @returns 
+     */
+    public static getFloatFromInt(value) {
+        // take 23 bits of integer, and divide by 2^23-1
+        return Math.floor((value & 0x007fffff) * (1.0 / 8388607.0));
+    }
+
+    /**
+     * Converts an integer to a single-byte integer
+     * @param value integer
+     * @returns 
+     */
+    public static getByteFromInt(value) {
+        // take the most significant byte from the 23-bit value
+        return value >> (23 - 8);
+    }
+
+    /**
+     * Returns a new random number generator object with the same seed state as 
+     * the current random number generator object
+     * @returns 
+     */
+    public clone(): Rand {
+        let result = new Rand();
+        result._x = this._x;
+        result._y = this._y;
+        result._z = this._z;
+        result._w = this._w;
+        return result;
+    }
+
+    /**
+     * Generate a random number
+     * @returns 
+     */
+    public get() {
+        let t = this._x ^ (this._x << 11);
+        this._x = this._y;
+        this._y = this._z;
+        this._z = this._w;
+        return (this._w = this._w ^ (this._w >> 19) ^ (t ^ (t >> 8)));
+    }
+
+    /**
+     * Randomly generate a floating-point number 0.0 to 1.0
+     * @returns 
+     */
+    public getFloat() {
+        return getFloatFromInt(this.get());
+    }
+
+    /**
+     * Randomly generates signed floating-point numbers -1.0 to 1.0
+     * @returns 
+     */
+    public getSignedFloat() {
+        return this.getFloat() * 2.0 - 1.0;
+    }
+}