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46 Chapter 17: Rendering
Rays/Sample has a high value and Adaptive
Undersampling is on.
Other Tips for Using the Light Tracer
• To improve rendering time, use the Object
Properties dialog (page 1–117) to disable light
tracing(orradiositysolving)forobjectsthat
don’thaveagreatimpactonthefinaleffect.
Tip: Yo u c a n a l s o u s e t h e Advanced Lighting
Overr ide material (page 2–1601) to alter the
effect of light tracing on particular objects.
For example, if you encounter visual artefacts
with a bump-mapped material, convert it to
an Advanced Lighting Override material and
reduce the Indirect Light Bump Scale value.
• Experiment with the Adaptive Undersampling
group settings, which restrict lig ht tracing to
the areas of your scene that need it.
• To increase the amount of color bleeding,
increase the values of both Bounces and Color
Bleed. Color bleeding is usual ly a subtle effect.
• If there are glass objects in the scene, increase
the Bounces value to an amount g reater than 0.
But be aware that this increases rendering time.
• If the main scene lig hting is a Skylight (page
2–1296), and you need specular high lights in
your scene, add a second light: for example,
a Directional light that parallels the Skylight.
Make sure Shadows are turned on for this light,
and on t he light’s Advanced Effects rollout (page
2–1341), turn off Diff use.
If the objects w ith highlig hts don’t g reatly
affect shadows or color bleeding, you can
leaveDiffuseonforthislight,anduseObject
Properties to exclude the objects from light
tracing.
• Set Key filters are not tak en into account when
you animate Light Tracer settings. If you wish
touseSetKeytocreatekeysforanimatingthe
Light Tracer parameters,
Shif t +right-click the
spinner to create those keys.
Impor tant: If you use a texture map with the
Skylight, you should use an image-processing
program to thoroughly blur the map before using
it. This helps reduce variance and the number of
rays needed for light tracing. Yo u can blur the map
beyond recognition, and it will still look correct when
used for regathering.
Procedures
TosetupascenefortheLightTracer:
This is a typical use case.
1. Create the geometry for an outdoor scene.
2. Add a Skylight (page 2–1296) to illuminate it.
Oneormorespotlightscanalsoworkwell.If
youusethephysicallybasedIESSunorIESSky
lights, using an exposure control (page 3–293) is
essential.
3. Choose Rendering > Advanced Lighting. On
the Select Advanced Lig hting rollout, choose
Light Tracer from the drop-down list.
Active should turn on, and the Parameters
rollout for the Light Tracer should appear.
4. Adjust the Light Tracer parameters,
activate the viewport to render, and then click
Render Scene.
5. Adjust your rendering sett ings, and t hen click
Render.
The scene renders with soft-edged shadows and
color bleeding.