Autodesk 62205-051408-9001 User Guide - Page 319

Controlling Speed, Understanding Speed, Slope of the Curve is Speed

Page 319 highlights

Controlling Speed ❚❘❘ Controlling Speed You can control the speed of an object along its motion path with the Speed channel. The speed adjustments do not affect the motion path itself. The Speed channel is only available for the Composite, Paint, Mask, Selection, and Particles operators. For other items where you control position (such as the flare center for a Lens Flare filter), you can still control speed using position keyframes and their tangent handles in the Timeline. This is also how you control speed if you disable the Speed channel. To simplify the descriptions in this section, the word object is used to refer to any item that can have a motion path and has a Speed channel. As mentioned above, this includes composite layers and objects, as well as Paint, mask, selection, and emitter objects. You can see a motion path in the viewport when the operator (such as Paint) is displayed in the viewport and the object is selected. The Speed channel is disabled by default. If you want to enable by default the Speed channel, go to the Combustion Preferences by choosing File | Preferences (CTRL+;), click the Animation category under Host, and enable Use Speed Channel By Default. Understanding Speed Speed is distance divided by time. When you plot Distance against Time (on a graph such as the Timeline), the slope of the curve is speed. For the Speed channel, the two axes for the graph are percent completion of the distance along the motion path (instead of Distance) and Time. The slope of the curve is still speed, and by changing the curve, you change speed. To use the Speed channel in Combustion, you need to understand these concepts: • The slope of the Speed curve is speed. • The distance along the motion path is expressed as a percentage. • By manipulating the Speed curve, you can achieve Ease In, Ease Out, and backwards movement on the motion path. • The Speed channel can be disabled; make sure it is enabled if you want to use it. Slope of the Curve is Speed When you make a motion path, it has a specific distance between the start and end. The difference in time between the start and end keyframes is the total time. So if you divide the distance by the total time, Speed Curve for a Paint Object Yellow box indicates Speed channel is enabled 303

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Controlling Speed
303
❚❘❘
Controlling Speed
You can control the speed of an object along its
motion path with the Speed channel. The speed
adjustments do not affect the motion path itself.
The Speed channel is only available for the
Composite, Paint, Mask, Selection, and Particles
operators.
For other items where you control position (such as
the flare center for a Lens Flare filter), you can still
control speed using position keyframes and their
tangent handles in the Timeline. This is also how you
control speed if you disable the Speed channel.
To simplify the descriptions in this section, the word
object is used to refer to any item that can have a
motion path and has a Speed channel. As mentioned
above, this includes composite layers and objects, as
well as Paint, mask, selection, and emitter objects.
You can see a motion path in the viewport when the
operator (such as Paint) is displayed in the viewport
and the object is selected.
The Speed channel is disabled by default. If you want
to enable by default the Speed channel, go to the
Combustion
Preferences by choosing
File | Preferences (
C
TRL
+;
), click the Animation
category under Host, and enable Use Speed Channel
By Default.
Understanding Speed
Speed is distance divided by time. When you plot
Distance against Time (on a graph such as the
Timeline), the slope of the curve is speed.
For the Speed channel, the two axes for the graph are
percent completion of the distance along the motion
path (instead of Distance) and Time. The slope of
the curve is still speed, and by changing the curve,
you change speed.
To use the Speed channel in
Combustion
, you need
to understand these concepts:
The slope of the Speed curve is speed.
The distance along the motion path is expressed as
a percentage.
By manipulating the Speed curve, you can achieve
Ease In, Ease Out, and backwards movement on
the motion path.
The Speed channel can be disabled; make sure it is
enabled if you want to use it.
Slope of the Curve is Speed
When you make a motion path, it has a specific
distance between the start and end. The difference in
time between the start and end keyframes is the total
time. So if you divide the distance by the total time,
Speed Curve for a Paint Object
Yellow box indicates Speed channel is enabled