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A Ramp force is
a force that steadily increases or decreases in magnitude over time. The Ramp
force may act in a single direction or may also change directions.

The sum of the
force on a heavy wagon being pushed uphill by an increasingly tired person is
an example of a Ramp force. The force of gravity pulls downhill on the wagon
with a Constant force throughout. The pusher starts out strong, pushing the
load quickly uphill. As he becomes increasingly tired, the upward force he exerts
on the wagon decreases. When gravity begins to win, the wagon no longer moves
uphill, and slowly begins to move downward in response to gravity. The Ramp
force in this situation starts out as a positive force, pushing the wagon uphill,
and decreases steadily until it is a negative force, pulling the wagon downhill.

Steering
wheels, joysticks and a full force feedback mouse can simulate Ramp forces.
A tactile feedback mouse cannot.

**Direction**

The direction
tells you where the force comes from; the location of the origin of the force.
Direction for a Ramp force can be specified in Cartesian or polar coordinates,
in the same way as for a Constant force.

The direction
of a Ramp force specifies the direction whenever the magnitude of the Ramp
force is greater than zero. When the force magnitude is less than zero, the
direction of the force will be the opposite of that specified for the force
as a whole.

**Duration**

Duration specifies
the amount of time the effect lasts in milliseconds. It can range from any
finite value greater than 0 to infinity, though an infinite-duration Ramp
force will never reach its final magnitude.

**Gain**

Gain is a factor
with which you can scale all the magnitudes of the Ramp effect. It ranges
from 0 to 10000, where a gain of 10000 is equivalent to multiplying the forces
throughout the effect by a factor of 1.

**Magnitude**

Magnitude specifies
the strength of the force. Two magnitudes are specified for Ramp forces: starting
and ending magnitudes. The force begins at the starting magnitude, then changes
linearly over time to reach the ending magnitude. If the two magnitudes fall
either both positive or both negative then the force will either increase
or decrease in a single direction. If one is negative and the other positive,
then the force will decrease over time, reverse directions at some point and
then increase in strength.

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