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1314 Chapter 15: Lights and Cameras
special photometric lights and an environment
shader that all work together:
• The mr Sun photometric light is responsible for
the sun light; the direct lig ht f rom the sun.
The scene is lit by mr Sun only.
• The mr Sky photometric light is responsible
for the skylight; it simulates the real-world
phenomenon of indirect light created by the
scattering of sunlight in the atmosphere.
The scene is lit by mr Sk y only.
• The mr Physical Sky environment shader is
responsible for the visible representation of
the sun disk and the sky, b oth to the camera
and in reflections and refraction, as well as for
the virtual ground plane (gray in the following
illustration).
mr Physical Sky is visible, but no lighting is present in th e
scene.
While you c an use these separately, their intended
functionality is unleashed only when used
together. mr Sun and mr Sky are meant primari ly
for use within the 3ds Max Daylight system (page
1–418). When used in combination, this solution
is called Sun & Sky.
Note: Sun & Sky is a true high-dynamic range
photometric l ighting system that requires the
Logarithmic Exposure Cont rol to be enabled.
In some of the mental ray rendering presets
(page 3–23), such as those star ting with
“mental.ray.daylight,” this is done automatically.
Also, when you add a Daylight System f rom the
Create menu, you have the option to activate
Logarithmic Exposure Control automatically.
Using Sun & S k y with SSS Materials
To u s e a m e n t a l r ay fast SSS material (page 2–1583)
together with the high-dynamic range Sun &
Sky solution, be sure to turn on Scatter Indirect
Illumination on the material’s Advanced Options
rolloutsothatthematerialcanscattertheskylight,
which is considered indirect.
Also, tur n off Screen (Soft) Compositing Of
Layers, also on the Advanced Options rollout;
otherwise the output of the SSS shaders is clamped
to a low dy namic range and will appear to render
black.