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42 Chapter 17: Rendering
dialog for that object. Image motion blur blurs
the object by creating a smearing effect rather
than multiple images. It takes c a mera movement
into account. Image motion blur is applied after
scanline rendering is complete.
ThecoinontherighthasImageMotionBlurapplied
You can’t put image motion blur on objects that
change their to pology.
Tip: When blurred objects overlap, sometimes
blurring doesn’t work correctly and there are gaps
in the rendering. Because image motion blur
is applied
after rendering, it can’t account for
object overlap. To fix this problem, render each
blurred object s eparately, to a different layer, and
then composite the two layers using the Alpha
Compositor in Video Post.
Note: Imagemotionblurdoesn’tworkforNURBS
objects that are animated so their tessellation
(
surface approximation (page 1–1241) )changes
over time. This happens when sub-objects are
animated independently of the top-level
NURBS
model (page 3–1074)
.Nordoesimagemotion
blur work on any of the following:
• Anything with an Optimize.
• Any primitive with animated segme nts.
• MeshSmooth of any type with a "Smoothness"
value (u nder iterations) other than 1.
• MeshSmooth on polygons w ith Keep Faces
Convex on.
• Anyth ing with Displacement Material.
In general, if you have objects w ith changing
topology, use scene or object motion blur rather
than image motion blur.
Apply —Turns image motion blur on or off globally
for the entire scene. Any objects that have their
Image Motion Blur property set are rendered with
motion blur.
Duration—Specifies how long the "virtual shutter"
is open. When this is set to 1.0, the virtual shutter
is open for the entire duration b e tween one frame
and the next. The hi gher the value, the greater the
motion blur effect.
Apply to Envir onment Ma p—When set, image
motion blur is applied to the environment map
as well as to the objects in t he scene. The effect is
noticeable when the camera orbits.
The environment map should use Env ironment
mapping: Spherical, Cylindrical, or Shr in k-Wrap.
The image motion blur effect doesn’t work w ith
Screen-mapp ed environments.
Transparency—When on, image motion blur works
correctly with transparent objects that overlap.
Applying image motion blur to transparent objects
can increase rendering time. Default=off.
Auto Reflect/Refract Maps group
Rendering Iterations—Sets the number of
inter-object reflections in non-flat automatic
reflection maps. Although increasing this value
can sometimes enhance image quality, it also
increases rendering time for reflections.
Color Range Limiting group
Color Range Limiting allows you handle
over-brightness by toggling between either
Clamping or Scaling color componen ts (RGB)