8

Radiosity Workflows 57
imported to 3ds Max, the room will measure 244
units long (20’*12+4”).
Tip: Use the Measure Distance tool (page 2–15) to
quickly check dimensions in 3ds Max.
Physically Based Wor kflow
Use radiosity (page 3–50) to create physically
based lighting simulations. When doing so, keep
in mind the following:
• Scene dimensions: Make sure your scenes are
accurately dimensioned, with consistent units
(a light bulb in a room 120 meters high would
look a lot different than it would in a room 120
inches high).
• Lights: Yo u s h o u l d w o r k e x c l u s i v e l y w i t h
Photometric lights (page 2–1155) . You should
also make sure that the l ight intensities are
within a normal range.
• Natural Lighting: To s imulate natural light,
you should only use
IES sun (page 2–1163) and
IES Sky (page 2–1165) .Theseprovideaccurate
photometric representations of sunlight and
skylight based on a specified location, date and
time.
• Material Reflectance: You should ensure
that the materials you use in your scene have
a
reflectance value (p age 2–1274) within the
range of the physical materials they represent.
For example, a painted white wall should have
a maximum reflectance of approximately 80%;
however, a pure white color material (RGB:255,
255, 255) would have a reflectance of 100%.
This means that the material reflects 100% of
the energy received.
• Exp osu r e Cont r ol: Theexposurecontrolisthe
equivalent of the aperture of a camera. Make
sureyouenabletheexposurecontrolandseta
value that provides the final results you desire.
To process ra diosity for photometric lights using a
physically based work flow:
1.
Ensure that your geometry is set to a physically
correct scale and that the materials have valid
reflectance values.
2. Place photometric lights in y our scene. The
benefitofthisworkflowisthatitallowsyou
to place lights in your scene the same way you
would in the real world. You can create new
photometriclightsor,usingthe
asset browser
(page 3–505)
,draganddroppreset luminaire
objects (p age 1–108)
from the included library.
You can also refer to
Common Lamp Values
(page 2–1174)
.
3. Cho ose Rendering > Environment to display
the
Environment panel (page 3–268) .Select
thetypeofexposurecontrolyouwanttouse
(typical ly
Logarithmic (page 3–293) ).
4. Click Render Scene to preview the
lighting. At this stage, the radiosity will not be
processed but you c an quickly confirm that the
direct lig hting is correct. Adjust the position
of the lights if desired.
5. Choose Rendering > Advanced Lighting >
Radiosity. Make sure that Active is turned on.
6. On the Radiosity Parameters rollout, click
Start to process radiosit y. Once the Radiosity
calculation has been com p leted, you should
see your results in the viewports. The light
levels are stored with the geometry and you
can interactively navigate around the model
without reprocessing the scene.
7. Click Render Scene again. The renderer
will calculate the direct lighting and shadows,
and the radiosity solution (indirect lighting)
will be integrated as a modulated ambient light.