mental ray Architectural and Design Visualization Shader Library

2.6 Tips and Tricks 53There is one minor trade off:To correctly render the shadows of a material using this method one must either use causticsor make sure mental ray is rendering shadows in “segment” shadow mode.Using caustics naturally gives the most correct looking shadows (the above image was notrendered with caustics), but will require that one has caustic photons enabled and a physicallight source that shoots caustic photons.On the other hand, the mental ray “segment” shadows have a slightly lower performance thanthe more widely used “simple” shadow mode. But if it is not used, there shadow intensity willnot take the attenuation through the media into account properly 15 .2.6.2.6 Water and LiquidsWater, like glass, is a dielectric with the IOR of 1.33. Hence, the same principles as for glass(above) applies for solid bodies of water which truly need to refract things... for examplewater running out of a tap. Colored beverages use the same principles as colored glass, etc.Water into WineTo create a beverage in a container as in the image above, it is important to understand howthe mia material handles refraction through multiple surfaces vs. how the “real world” tacklesthe same issue.What is important for refraction is how the transition from one medium to another with adifferent IOR. Such a transition is known as an interface.15 But it could potentially still look “nice”.