@woosh/meep-engine/src/core/geom/3d/mat4/m4_invert.js

Pure JavaScript game engine. Fully featured and production ready.

/**
 * Inverts a 4x4 matrix
 * @see Adapted from glMatrix
 * @param {Float64Array|Float32Array|number[]|mat4} out
 * @param {Float64Array|Float32Array|number[]|mat4} input
 * @returns {boolean} true iff determinant is not 0, otherwise matrix is non-invertible and false is returned
 */
export function m4_invert(out, input) {

    const a00 = input[0],
        a01 = input[1],
        a02 = input[2],
        a03 = input[3];

    const a10 = input[4],
        a11 = input[5],
        a12 = input[6],
        a13 = input[7];

    const a20 = input[8],
        a21 = input[9],
        a22 = input[10],
        a23 = input[11];

    const a30 = input[12],
        a31 = input[13],
        a32 = input[14],
        a33 = input[15];

    const b00 = a00 * a11 - a01 * a10;
    const b01 = a00 * a12 - a02 * a10;
    const b02 = a00 * a13 - a03 * a10;
    const b03 = a01 * a12 - a02 * a11;
    const b04 = a01 * a13 - a03 * a11;
    const b05 = a02 * a13 - a03 * a12;
    const b06 = a20 * a31 - a21 * a30;
    const b07 = a20 * a32 - a22 * a30;
    const b08 = a20 * a33 - a23 * a30;
    const b09 = a21 * a32 - a22 * a31;
    const b10 = a21 * a33 - a23 * a31;
    const b11 = a22 * a33 - a23 * a32;

    // Calculate the determinant
    const det =
        b00 * b11 - b01 * b10 + b02 * b09 + b03 * b08 - b04 * b07 + b05 * b06;

    if (det === 0) {
        // determinant is 0, can't invert
        return false;
    }

    const inv_det = 1.0 / det;

    out[0] = (a11 * b11 - a12 * b10 + a13 * b09) * inv_det;
    out[1] = (a02 * b10 - a01 * b11 - a03 * b09) * inv_det;
    out[2] = (a31 * b05 - a32 * b04 + a33 * b03) * inv_det;
    out[3] = (a22 * b04 - a21 * b05 - a23 * b03) * inv_det;
    out[4] = (a12 * b08 - a10 * b11 - a13 * b07) * inv_det;
    out[5] = (a00 * b11 - a02 * b08 + a03 * b07) * inv_det;
    out[6] = (a32 * b02 - a30 * b05 - a33 * b01) * inv_det;
    out[7] = (a20 * b05 - a22 * b02 + a23 * b01) * inv_det;
    out[8] = (a10 * b10 - a11 * b08 + a13 * b06) * inv_det;
    out[9] = (a01 * b08 - a00 * b10 - a03 * b06) * inv_det;
    out[10] = (a30 * b04 - a31 * b02 + a33 * b00) * inv_det;
    out[11] = (a21 * b02 - a20 * b04 - a23 * b00) * inv_det;
    out[12] = (a11 * b07 - a10 * b09 - a12 * b06) * inv_det;
    out[13] = (a00 * b09 - a01 * b07 + a02 * b06) * inv_det;
    out[14] = (a31 * b01 - a30 * b03 - a32 * b00) * inv_det;
    out[15] = (a20 * b03 - a21 * b01 + a22 * b00) * inv_det;

    return true;
}