HW4: Macbeth color checker image
HW5: Cornell Box
HW6: BRDF
HW7: Mixture density (combined sampling)
HW8: Uniform participating media
HW9: Rayleigh scattering participating media
HW10: Subsurface Scattering
HW11: Dielectrics
HW12: "Cool" Image (actually a comparison of
different ray termination algorithms)