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Damper - Tactile effects library

A damper is something that resists motion. Dampers come in all forms ranging from mechanisms like shock absorbers to simple liquids like water or molasses. All dampers behave linearly, meaning that the faster you try to move a damper, the more resistance you feel. For instance, imagine holding a ping-pong paddle underwater and trying to move the broad face back and forth. If you move it very slowly, you feel almost no resistance to your motion, but the faster you try to move it back and forth, the harder it becomes.

The damper effect works on all full force feedback joysticks, steering wheels, gamepads and mice. It does not work on tactile feedback mice. The various properties of Damper allow you adjust things like how strong the effect is and in which direction it resists motion.

One use of a damper effect is to simulate being immersed in a liquid. A simple damper effect of mild strength will make the peripheral feel like it is moving while submerged in a light viscosity liquid like water. A maximum strength damper will feel more like moving through thick mud or molasses.

Another use of a damper is to simulate being on ice. Instead of offering resistance to motion, it is possible to actually add assistive forces to motion. The faster you try to move, the more it helps push you along in the direction you're already going, to the point of shoving you. The end result is like trying to move on ice. Moving very slowly is fine, but making a sudden movement can cause you to feel like you suddenly were shoved and make you lose control.


Center specifies how fast you need to be moving in order not to feel any resistance. Going back to the ping-pong paddle example, if Center is set to zero, this means you will not feel any resistance if you have zero motion. In other words, you only feel the viscous resistance if you start to move the paddle. If the Center is set to 1000, you will feel resistance unless you are moving at a rate of 1000 units per second. This is equivalent to a current running through the water in which you are holding the paddle. Now, holding the paddle still actually results in the resistance of the water current pushing against the motionless paddle. You actually have to move the paddle at the same rate as the water (1000 units per second in this case) to "go with the flow" and not feel any resistance. Also see Deadband, which affects the behavior of Center.


The Coefficient determines how strong or stiff the damper effect is. In other words, the greater the Coefficient, the more quickly the Damper forces increase as cursor velocity increases. Coefficient specifies how big a paddle you are holding underwater. A huge paddle will offer much more resistance to motion than a small paddle at the same paddle velocity, because of the much larger surface area plowing through the water. A Coefficient of zero causes no ramp-up in force for an increase in velocity, so no Damper will be felt. However, Coefficient also works in conjunction with Saturation to determine the overall level of resistance in the Damper, so also see the Saturation section.

Using the Positive Coefficient and Negative Coefficient parameters, you can create asymmetric dampers that feel different when moving in different directions. Here, positive and negative really mean the positive direction and the negative direction (e.g., right versus left, down versus up); it has nothing to do with whether the parameter has a positive or negative value. For example, a bicycle pump offers resistance when you push down, but none when you pull up. It behaves like a damper with a large Positive Coefficient and a zero-valued Negative Coefficient.

The range for Coefficient is -10000 to +10000. Using a negative value for Coefficient instead of a positive value will cause the peripheral to be pushed in the direction of motion instead of resisting it and works well for simulating icy or slippery conditions.


Deadband sets the range of cursor velocities over which the Damper effect is not active (no forces are felt). In the underwater paddle example, having a Deadband of 0 means you will start feeling resistance as soon as you start moving at the slightest speed. However, a non-zero Deadband means the resistance will not be felt until you start moving faster than the (Deadband/2) speed away from Center.


Direction specifies whether the damper acts left and right along the X-axis, up and down along the Y-axis, or at an angle. The damper can also act both left and right as well as up and down. A damper at an angle is like a left and right damper that has been rotated by some angle. See the Spring and Constant Force descriptions for more details on Direction.


While you can specify a Duration for a damper, by default its duration is infinite. It is unusual to specify a non-infinite duration for a damper.


Gain is a factor with which you can scale the entire damper effect. It ranges from 0 to 10000 where 0 makes the damper effect unnoticeable and 10000 does not change the damper effect at all.


Minimum specifies the minimum velocity level at which the damper forces become active. This property is essentially the same as Deadband, and is used for a zero-centered Damper.


Saturation sets the maximum force output possible for the effect and has a range of 0 to +10000. Setting Saturation to +10000 means there should be no limit on the force output for this Damper; the Damper effect should exert the force determined by how big a paddle you're holding and how fast you're moving the paddle all the way up to the maximum force possible out of the device. Setting the Saturation to 0 means the total force output for this damper should be limited to 0, which means you will never feel anything from the damper no matter how quickly you move or how large the Coefficient. Setting Saturation to +5000 means the force output for this damper should be limited to half the maximum force possible from the device. See the figure at the end of the Damper section for a graphical representation of Saturation.

Like Coefficient, there is a Positive Saturation and a Negative Saturation to allow for the existence of asymmetric limits. Positive Saturation sets the limit in the positive direction (the Direction specified for the Damper) and Negative Saturation sets the limit in the negative direction (the opposite direction).


Viscosity, a property that only applies to the Damper effect, is equivalent to Coefficient. However, only one value of Viscosity can be specified for a Damper effect, for all directions of motion. It is therefore impossible to create an asymmetric Damper by specifying the Viscosity property.

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