import Matrix4 from "./Matrix4";

export function identityMatrix(size: number): Float32Array {
    const mat = Array<number>(size*size).fill(0);
    return new Float32Array(
        mat.map((_, index) =>
            index % 5 === 0 ? 1 : 0
        ));
}

export function perspMat(fovDeg: number, aspect: number, near: number, far: number): Matrix4 {
    const f = Math.tan(Math.PI * 0.5 - 0.5 * fovDeg);
    const rangeInv = 1.0 / (near - far);

    return new Matrix4([
        f / aspect, 0, 0, 0,
        0, f, 0, 0,
        0, 0, (near + far) * rangeInv, -1,
        0, 0, near * far * rangeInv * 2, 0
    ]);
}