i0=0;
    i1=1;
    i2=2;
    var n;
    normals = [];

    for (n = 0; n < vertices.length; n++)
        normals.push([0,0,0]);


    for (i= 0; i<triangles.length; i++) {
        triangle = triangles[i];
        a = normalize(sub(vertices[triangle[i1]] , vertices[triangle[i0]]));
        b = normalize(sub(vertices[triangle[i2]] , vertices[triangle[i0]]));

        n = normalize(mult(a,b));

        normals[i0] = add(normals[i0], n);
        normals[i1] = add(normals[i1], n);
        normals[i2] = add(normals[i2], n);


    }

    for (n= 0; n < normals.length; n++) {
        normals[n] = normalize(normals[n]);
    }