2008

Combustion or Flame. There are plug-ins for compositors that generate motion
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 that 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 to 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 Motion Blur
camera effect must be turned off. Also, some mental ray materials do not support
render elements.
Controls on the element's rollout let you improve the precision of the motion
data saved in the rendering. See the procedure, following.
Procedures
To render a velocity element for an animation 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 specific Maximum Velocity value will give you more accurate
velocity data.
5 Turn off Update.
Now the Maximum Velocity will remain constant.
6166 | Chapter 18 Rendering