9

Radiosity Workflows 59
Lighting Analysis
After you generate a radiosity solution, you can
use the Lighting Analysis tool (page 3–76) to
analyze the lighting levels in your scene. This
dialog provides data on material reflectance,
transmittance, and luminance.
You can a lso interactively v isualize the l ight levels
in the scene by using the Pseudo Color Exposure
Control (page 3–300). Rendering to a rendered
frame window displays an additional rendered
frame with a legend below the image. The legend
correlates lighting levels and color values.
If you need to generate a lighting report, you can
use t he Lighting Data Exporter utility (page 3–303)
to export the luminance and illuminance data to
a 32-bit LogLUV TIFF file (page 3–634) or a pair
of PIC files (page 3–628) (one each for luminance
and illuminance).
Note: To obtain the most accurate quantitative
analysis of lighting levels, you should avoid u sing
colored materials and diffuse maps.
Non-Physically Based Work flow
You don’t necessarily have to work with physically
based lights and materials in order to incorporate
radiosity effects into your renderings. But there
are a number of issues that you need to consider:
• Lights : Because the radiosit y engine is
physically based, Standard lights (page 2–1288)
are interpreted by the engine as Pho t ometric
lights (page 2–1301).Forexample,aStandard
Spot light with a multiplier value of 1.0 will be
translated as a Physical ly Based Spot light with
an intensity value of 1500 candelas (default
value). This translation value corresponds to
the Physical S cale value in the var ious exposure
controls.
In addition, if your Standard lights use
custom attenuation settings (for example, no
attenuation, manual attenuation, or linear
deca y), the radiosity engine will alwa ys solve
for these lights using the ph ysically correct
InverseSquareattenuation.Thismeansthat
theamountofenergythatbouncesbetween
surfaces might not b e equivalent to the way the
Standard lights render.
• Natural Lighting: To simulate natural lighting
w ithout using the physically based workflow
described above, you can only use a Direct Light
(page 2–1292) for the Sun and Skylight (page
2–1296) to produce skylight (page 3–1012).
• Exp osur e Control: Since Standard lights are
not physically based, you should only use
exposure controls for the radiosity solution.
Use the Logarithmic Exposure Control (page
3–297), making sure to tur n on Affect Indirect
Only. The Brightness and Contrast controls
oftheexposurecontrolwillonlyaffectthe
radiosity solution and your lights will render
as usual.
To process r adiosity with standard lighting:
1.
Ensure that your geometry is set to a physically
correct scale.
2. OntheCreatepanel,clickLights.
Create and position standard lights (page
2–1288) in your scene.
3. Click Render Scene to preview the
lighting. At this stage, the radiosity will not be
processed, but you can quickly confirm that the
direct lighting is correct. Adjust the position
of the lig hts if desired.
4. Choose Rendering > Advanced Lighting >
Radiosity. Make sure that Active is turned on.
5. On the Radiosity Parameters rollout, click
Start to process radiosit y. Once the Radiosity
calculation has been completed, you should see
your results in the viewports.