faster than mental ray

mental ray:

RC   0.2  info :   type                       number   per eye ray
RC   0.2  info :   eye rays                       971978          1.00
RC   0.2  info :   shadow rays                    458468          0.47

rendering time: 9 seconds

elvish ray:

number of eye rays: 867168
number of shadow rays: 427724
shadow rays per eye ray: 0.493242

rendering time: 5 seconds