Periodic effects are vibrations, like the buzz of an electric razor, the whir of a cooling fan, the shaking of your wheels on uneven pavement, or the deep rumble of a distant volcano. Vibrations are all around us. Anything that buzzes or rattles can be modeled by a periodic effect.
Periodic means something that regularly repeats; a periodic effect consists of a series of individual pulses or "waves" repeated over and over again. Think of waves blown by the wind passing over the surface of a lake. If you put your hand in the water, you would feel the crest and trough of each wave as they pass one by one by your hand.
Periodic effects are supported by all TouchSense mice, joysticks, and wheels. Periodic effects affect a mouse regardless of its position on the screen. In other words, a Periodic is a passively experienced effect.
Direction
Specifies the axis along which the periodic effect plays. This property is ignored for a tactile feedback mouse, as the force is always up-down.
Duration
The duration determines how long the entire Periodic effect lasts. It has no effect on the period.
Envelope
An envelope allows you to change the level of a Periodic as it plays. It affects the entire effect over its whole duration, not the individual repeating cycles. If you are making a Periodic simulating the feel of a passing train, you might use an envelope to make the shaking swell up from nothing as the train approaches, and then decay again as the train heads away.
An envelope has both an attack portion and a fade portion; each of these has an associated level and time. During the beginning, or attack portion of the effect, the force intensity, or level, ramps from the attack level to the effect's overall magnitude over the attack time. During the end, or fade portion of the effect, the level ramps from the effect's magnitude to the fade level over the fade time.
Gain
Gain is a factor with which you can scale the entire envelope of the 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, and does not change the size of the envelope at all. A Gain of 5000 would cut all the forces throughout the effect in half. Gain and magnitude are different in that the gain changes the entire size of the envelope whereas the magnitude only changes the strength of the sustained force.
Magnitude
The magnitude of a Periodic effect represents the sustain level of the effect: the maximum force on the device during the central, unchanging part of the envelope. A high magnitude means a strong vibration, whereas a magnitude below 100 may be too weak to be felt. Magnitude is applied in both the positive and negative directions; a value of 10,000 represents the maximum magnitude and will make the Periodic vibrate strongly in both directions.
A negative magnitude inverts the positive and negative directions, so it pushes in the opposite direction it would have if the magnitude had been positive. In the graphs above this has the effect of flipping the waveform around the blue line.
Offset
The offset indicates a value added to the amplitude of the Periodic. Unlike magnitude, it acts in a direction. For example, a positive offset increases the force in the positive direction (makes the waves higher above the blue line) and decreases it in the negative direction (makes the waves shorter below the blue line). A negative offset increases the force in the negative direction and decreases it in the positive direction.
Phase
The phase of a periodic effect is the point along the waveform where the effect begins. It is only relevant for low-frequency vibrations as you can't notice a phase-shift in a high-frequency vibration. With a phase of 0 the first waveform will play at the beginning. With a phase of 180 degrees the first waveform will play starting at its halfway point. The following table indicates where selected phase values in degrees lie along the various waveforms. m is the top of the wave, -m is the bottom, and 0 is the midpoint, where no force is applied in either direction.
270 square -m sawtooth up (3/4)m [reaches m just before cycle repeats]
sawtooth down (1/4)m [reaches 0 just before cycle repeats]
sine/triangle -m
Period
The period is how long a single repeating cycle (pulse) of the vibration lasts. This determines the "frequency" of the vibration. Periodics with shorter periods (higher frequencies) feel like buzzes. Periodics with longer periods (lower frequencies) feel like rumbles or taps.
The period has no effect on the overall duration of a Periodic.
Waveform
A Periodic's waveform is the "shape" of the repeated pulses. Shown below are the five basic waveform varieties: Square, Sawtooth Up, Sawtooth Down, Sine, and Triangle. The graphs display the force over time: area above the blue line means a force in the direction specified for the effect, area below the blue line means a force in the opposite direction.
Square. The most intense of all of the waveforms, due to its abrupt transitions.
Sawtooth Up. The waveform steadily rises and then drops suddenly after reaching a maximum force.
Sawtooth Down. The waveform steadily drops and then rises vertically after reaching a minimum force.
Sine. The smoothest of the vibrations.
Note that this waveform is not supported on the Logitech iFeel Mouse and MouseMan and will be played as a square wave on these mice.
Triangle. In between the square and the sine wave in terms of "smoothness" of the vibration.
Note that this waveform is not supported on the Logitech iFeel Mouse and MouseMan and will be played as a square wave on these mice.
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