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In a lighting effects engine, a sine wave moves a parameter smoothly back and forth, slowing down as it reaches each end, so it suits breathing dimmer pulses, sways, and circles. A sawtooth wave climbs steadily in one direction and then jumps straight back to the start, so it suits one-way effects such as running dimmer chases and rising color fades, but it looks rough on pan and tilt because a moving head cannot jump back instantly.
What an effects engine does
An effects engine, also called an FX engine, effect generator, or phaser on different consoles, takes one parameter of a fixture and moves it continuously around a value you set. That parameter can be dimmer, pan, tilt, a color channel, zoom, or anything else on a DMX channel. Instead of programming dozens of steps by hand, you choose a waveform and a few settings, and the engine calculates the values many times per second.
Most engines share the same controls, even if the names differ:
- Waveform: the shape of the movement, such as sine, sawtooth (ramp), triangle, or square.
- Size: how far the parameter moves, sometimes called amplitude or range.
- Base or offset: the center point the movement happens around.
- Rate: how fast one full cycle runs, in BPM, cycles per minute, or seconds per cycle.
- Phase: where in the cycle a fixture starts, from 0 to 360 degrees.
- Spread: how the phase is shared out across a group of fixtures, which is what turns a single movement into a wave across a row.
Sine waves: smooth, with soft turns at each end
A sine wave changes fastest as it passes through the middle and slows to a stop at the top and bottom before turning around. That is why it looks natural on lights: nothing hits an end and bounces. On a dimmer it reads as breathing. On pan or tilt it reads as a sway, like something hanging on a string.
Because it slows at each end, a sine also spends more of its time near the extremes than in the middle. On a dimmer effect, the light lingers at bright and at dim, with quicker transitions between them.
Sine waves are the basis of the most common moving head shape. Run pan on a sine and tilt on the same sine shifted by 90 degrees, and the beam traces a circle. Run tilt at twice the rate of pan and you get a figure eight. Many engines offer these as ready-made shapes, but they are built from sine waves underneath.
Sawtooth waves: a steady ramp, then a reset
A sawtooth wave rises in a straight line from its low point to its high point, then drops straight back to the start and repeats, like the teeth of a saw. A reverse sawtooth, sometimes called a ramp down, does the opposite: it jumps to the top and then falls steadily.
That shape has a clear direction, and that is what it is good for:
- Dimmer: a ramp down with spread across a row of fixtures gives the classic running chase, each fixture snapping on and fading out, so the light appears to travel with a tail behind it. Swap to a ramp up and the effect reads as building rather than trailing.
- Color: a slow sawtooth on a color channel or a hue setting gives a one-way color roll that never reverses.
- Intensity builds: a very slow sawtooth makes a steady rise that resets, useful under music that builds in phrases of the same length.
On pan and tilt, sawtooth is usually a poor choice. The wave asks for an instant jump back to the start, but moving head motors can only move so fast. The fixture makes a quick visible swing back, often with some overshoot, and the beam whips across the room. If you want a back-and-forth sweep, use a triangle wave, which moves at a steady speed in both directions, or a sine if you want softer turns.
Quick comparison
| Waveform | Shape over one cycle | Works well on | Watch out for |
|---|---|---|---|
| Sine | Smooth rise and fall, slows at each end | Dimmer breathing, pan and tilt sways, circles and figure eights | Can look lazy at slow rates on fast music |
| Sawtooth (ramp up) | Steady rise, instant drop | Dimmer builds, one-way color rolls | The reset on pan and tilt |
| Reverse sawtooth (ramp down) | Instant rise, steady fall | Dimmer chases with a trailing tail | Same reset problem on movement |
| Triangle | Steady rise, steady fall | Even sweeps across a stage or audience area | Sharper turnarounds than a sine |
| Square | On, then off | Flash and blink effects, alternate fixtures | Can look like a strobe at high rates |
Phase and spread: turning one fixture's effect into a wave
With phase at 0 on every fixture, all of them do the same thing at the same time. That is sometimes what you want, such as a whole wash breathing together. To make the effect travel across a row, spread the phase.
For one complete wave across the row, divide 360 degrees by the number of fixtures. With 8 fixtures, each one is offset by 45 degrees from its neighbor; with 6, by 60 degrees. Spread 720 degrees across the same row and you get two waves at once. Set alternate fixtures 180 degrees apart and odd and even fixtures move opposite each other, which is a simple and effective look for beam moving heads.
The fixture order matters. If the wave runs the wrong way across the stage, reverse the selection order or the spread, depending on your software.
Settings that make or break the look
- Size on pan versus tilt. Pan often covers about 540 degrees and tilt much less, so the same size value moves pan further than tilt. If your circle comes out as an oval, increase the tilt size or reduce pan until it looks round from the audience.
- Rate against the fixture's speed. A large, fast movement can ask more than the motors can deliver. The fixture falls behind and the shape shrinks or turns jerky. Reduce size or rate first.
- Fine channels. Slow, small movements can show visible steps on 8-bit pan and tilt. If the fixture offers a mode with 16-bit pan and tilt, use it for slow effects.
- Dimmer curves. A sawtooth on a fixture with a linear dimmer can look like most of the change happens near the bottom of the fade. If the fixture menu offers other dimmer curves, try them, or check the manual.
- Tempo. Many engines can follow tap tempo or BPM. Set dimmer chases to the beat and slow movements to half or quarter time, so the room is not busy.
If your controller has no effects engine
Most budget 192-channel DMX controllers do not have waveform effects; they run scenes and chases. You can still get close. A two-step chase between a bright and a dim scene, with the fade time set close to the step time, gives a sine-like pulse. A chase that steps across fixtures one at a time gives a basic running effect, without the fading tail.
For real waveform effects, lighting software on a laptop with a USB-to-DMX interface is the budget route. Free software such as QLC+ includes shape generators for pan and tilt and matrix effects for color and dimmer. Any DMX moving head with pan and tilt channels, such as UKING ZQ02356 175W moving head, can run these effects once it is patched with the correct channel mode.
FAQ
Is a sawtooth wave the same as a ramp?
Yes. In most lighting software, ramp and sawtooth mean the same shape: a steady rise followed by an instant reset. A reverse sawtooth or ramp down is the same shape upside down.
Why does my moving head circle look like an oval?
Pan and tilt cover different ranges, so equal size values give unequal movement. Your viewing angle onto the wall or floor also stretches the shape. Adjust tilt size relative to pan until it looks round from where the audience sits.
Which waveform is best for a slow, calm dimmer effect?
Sine. It eases into the bright and dim points instead of hitting them, which reads as breathing rather than flashing. Keep the size moderate so the light never goes fully dark.
Why does my effect look steppy?
Usually the movement is slow and small on 8-bit pan and tilt, or the rate is higher than the fixture can follow. Switch to a 16-bit channel mode if the fixture has one, and reduce rate or size.
