sh.js

// Settings
var encode_color =   new THREE.Vector3(1, 0, 0);
var encode_dir =     new THREE.Vector3(0, 1, 0);
var decode_dir =     new THREE.Vector3(0, 1, 0);

// SH Constants
var fConst00 = Math.sqrt( 1/4 * Math.PI );
var fConst01 = Math.sqrt( 2/4 * Math.PI );
var fConst02 = Math.sqrt( 3/4 * Math.PI );
var fConst03 = Math.sqrt( 4/4 * Math.PI );

function Encode( dir, color )
{
    var sh = new Array(4);
    
    // sh[0] += colour * fConst00;
    var first = new THREE.Vector3(color.x, color.y, color.z);
    first.multiplyScalar(fConst00);
    sh[0] = first;
    
    // sh[1] += colour * fConst01 * dir.x;
    var second = new THREE.Vector3(color.x, color.y, color.z);
    second.multiplyScalar(fConst01);
    second.multiplyScalar(dir.x);
    sh[1] = second;
    
    // sh[2] += colour * fConst02 * dir.y;
    var third = new THREE.Vector3(color.x, color.y, color.z);
    third.multiplyScalar(fConst02);
    third.multiplyScalar(dir.y);
    sh[2] = third;
    
    // sh[3] += colour * fConst03 * dir.z;
    var fourth = new THREE.Vector3(color.x, color.y, color.z);
    fourth.multiplyScalar(fConst03);
    fourth.multiplyScalar(dir.z);
    sh[3] = fourth;

    return sh;
}

function Decode( dir, sh )
{
    var color = new THREE.Vector3( 0, 0, 0 );
    
    // color += sh[0];
    color.add(color, sh[0]);
    
    // color += sh[1] * dir.x;
    sh[1].multiplyScalar(dir.x);
    color.add(color, sh[1]);
    
    // color += sh[2] * dir.y;
    sh[2].multiplyScalar(dir.y);
    color.add(color, sh[2]);
    
    // color += sh[3] * dir.z;
    sh[3].multiplyScalar(dir.z);
    color.add(color, sh[3]);
    
    return color;
}

// Encode, Decode
var output_sh = Encode(encode_dir, encode_color);
var output_color = Decode(decode_dir, output_sh);

// Output Result
alert("Decoded Color: \n[" + output_color.x + "," + output_color.y + "," + output_color.z + "]");