// Check if the surface point is in shadow
            Vector3D poffset;
            poffset = new Vector3D(p.x+TINY*l.x, p.y+TINY*l.y, p.z+TINY*l.z);
            Ray shadowRay = new Ray(poffset, l);
            if (shadowRay.trace(objects))
                break;

            // Illuminate point
            float lambert = Vector3D.dot(n, l);
            if (lambert > 0) {
                // add in diffuse relectance contribution to color
                if (kd > 0) {
                    r += kd*lambert*ir*light.ir;
                    g += kd*lambert*ig*light.ig;
                    b += kd*lambert*ib*light.ib;
                }