const PI = Math.PI
const PI2 = PI * 2
const PIH = PI * 0.5
const cosFromSin = (sin, angle) => {
    const pih = PI / 2;
    const pi2 = PI * 2
    const cos = Math.sqrt(1.0 - sin * sin);
    const a = angle + PIH;
    const b = a - parseInt(a / PI2) * PI2;
    if (b < 0.0)
        b = PIH + b;
    if (b >= PI)
        return -cos;
    return cos;
} 

export class Mat4 {

    constructor() {
        this.data = [
            0, 0, 0, 0,
            0, 0, 0, 0,
            0, 0, 0, 0,
            0, 0, 0, 0
        ]
    }

    set(m00, m01, m02, m03, m10, m11, m12, m13, m20, m21, m22, m23, m30, m31, m32, m33) {
        const d = this.data
        d[0] = m00; d[4] = m01; d[8] = m02; d[12] = m03;
        d[1] = m10; d[5] = m11; d[9] = m12; d[13] = m13;
        d[2] = m20; d[6] = m21; d[10] = m22; d[14] = m23;
        d[3] = m30; d[7] = m31; d[11] = m32; d[15] = m33;
        return this
    }

    identity() {
        this.set(
            1, 0, 0, 0,
            0, 1, 0, 0,
            0, 0, 1, 0,
            0, 0, 0, 1
        )
        return this
    }
    
}