Face.java

Vector3f v1 = new Vector3f(this.verts[0].getPosition().x, this.verts[0].getPosition().y, this.verts[0].getPosition().z);
Vector3f v2 = new Vector3f(this.verts[1].getPosition().x, this.verts[1].getPosition().y, this.verts[1].getPosition().z);
Vector3f v3 = new Vector3f(this.verts[2].getPosition().x, this.verts[2].getPosition().y, this.verts[2].getPosition().z);
Vector3f v4 = this.verts.length > 3 ? new Vector3f(this.verts[3].getPosition().x, this.verts[3].getPosition().y, this.verts[3].getPosition().z) : null;

if (v4 == null)
{
    Vector3f v2c = new Vector3f(v2.x, v2.y, v2.z);
    Vector3f v1c = new Vector3f(v1.x, v1.y, v1.z);
    v1c.sub(v2c);
    Vector3f v3c = new Vector3f(v3.x, v3.y, v3.z);
    v3c.sub(v2c);
    Vector3f c = new Vector3f();
    c.cross(v1c, v3c);
    c.normalize();
    Normal normal = new Normal(c);
    return normal;
}
else
{
    Vector3f v2c = new Vector3f(v2.x, v2.y, v2.z);
    Vector3f v1c = new Vector3f(v1.x, v1.y, v1.z);
    v1c.sub(v2c);
    Vector3f v3c = new Vector3f(v3.x, v3.y, v3.z);
    v3c.sub(v2c);
    Vector3f c = new Vector3f();
    c.cross(v1c, v3c);
    c.normalize();

    v1c = new Vector3f(v1.x, v1.y, v1.z);
    v3c = new Vector3f(v3.x, v3.y, v3.z);

    Vector3f v4c = new Vector3f(v4.x, v4.y, v4.z);
    v1c.sub(v4c);
    v3c.sub(v4c);
    Vector3f d = new Vector3f();
    d.cross(v1c, v3c);
    d.normalize();

    Vector3f avg = new Vector3f();
    avg.x = (c.x + d.x) * 0.5f;
    avg.y = (c.y + d.y) * 0.5f;
    avg.z = (c.z + d.z) * 0.5f;
    avg.normalize();
    Normal normal = new Normal(avg);
    return normal;
}