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138 Chapter 17: Rendering
blur; for example, those created by RE:Vision
Effects, Inc.
The advantages of rendering a Velocity element are
that the composition application might give you
finer control over the motion blur than 3ds Max
does; you can render a “beauty” frame t hat does
not contain motion blur; and the Velocity element
is quicker to render than using one of the 3ds Max
motion-blur effects.
Another use of the Velocity element is to re-time
clips rendered in 3D. There are specialized
applications that allow you to re-time an image
sequence, using velocity data t o generate more
accurate inbetween frames.
In the Velocity rendering, the motion information
is saved as RGB color information:.red saves
movement on the X axis, green saves Y-axis
movement, and blue saves Z-axis movement,
relative to the plane of the rendered frame.
The mental ray renderer supports this element, but
the mental ray Mot ion Blur camera effect must be
turned off
. Als o, some mental ray materials do not
support render elements.
Controls on the element’s rollout let you impro ve
the precision of the motion data s aved in the
rendering. See the procedure, following.
Procedure
To r ender a v elocity element for an ani mation
sequence:
1.
On the Render Scene dialog > Render Elements
panel > Render Elements rollout, click Add.
In the Render Elements dialog that appears,
highlight Velocity, and then click OK.
2. Highlight the Velocity element in the Element
Rendering list.
3. On the Velocity Element Parameters rollout,
turn on Update, then render several test frames.
(Choose frames where object velocity appears
to be the greatest.)
4. After each test frame, make a note of the
Maximum Velocity value. If you need to do
so, enter the largest of these values as the
Maximum Velocity to use.
Having a s pecific Maximum Velocity value will
give you more accurate velocity data.
5. Tu r n off Up date.
NowtheMaximumVelocitywillremain
constant.
6. Render the animation.
Interfa ce
Maximum Velocity—Enter a Maximum Velocity
value based on the result collected by Update.
Setting a Maximum Velocity increases the
precision of the motion information. See the
“Procedure,” above. Default=1.0.
Update—Turn on when you render test frames,
as described in the above procedure. After each
rendering, Maximum Velocity is set to the value
recorded by update. Use the largest of these values,
and then turn off Update before you render the ful l
animation. Default=off.
Note: The Update control does not work with
mental ray distributed bucket rendering.