Fixture Kinds and Types
A fixture in Light Stream is whatever the program controls on the output — a single LED of a strip, a pixel of a line, a linear wash on a facade, or a full-featured DMX fixture with moving mechanics. Every fixture has a kind — how it lights up and how it looks in the 3D View window — and a type — how many channels it has and what each channel means. The kind is responsible for the picture in the preview, the type is responsible for the data that goes out to the real equipment.
Both the kind and the type are set by a single choice: the fixture from the Fixture Library. Below is how the kinds differ from one another, what types are in the library, what channels are, and how addresses and universes are built from them.
Three Fixture Kinds
| Kind | How It Lights Up | What It's For | Beam Parameters |
|---|---|---|---|
| Pixel | Glows on its own, like a dot; there is no beam | Strips, lines, pixel screens, garlands — anything made of individual LEDs | There are no separate beam parameters: the fixture in the scene has Pixel Width, Pixel Height and Pixel Length |
| Linear | Washes a surface with a wide beam along the housing | Linear washes, wall lighting, cornices, window reveals | Length, Angle°, Depth |
| Spotlight | Gives a directional cone of light | Spotlights, narrow-beam architectural fixtures, moving fixtures | Angle°, Height |
The kind affects only how the fixture looks and lights up in the 3D View. On the Mapping field all fixtures are shown the same way — as dots and lines, and the kind has no effect at all on the DMX data. Choose it based on how the fixture actually lights up in real life: this determines how close the preview will look to the real object.
The kind is part of the type's description, but for a fixture already placed in the 3D scene it can be changed separately. Select the fixture or spline in the 3D View window and in Properties, under Display Settings, change the Fixture Beam Type — the angle, length and other beam dimensions are set right there as well.
What Defines a Fixture Type
The type is a description of the fixture taken from the library. It stores:
- how many channels the fixture has and what each of them means;
- the fixture's kind and its beam dimensions;
- whether it is a moving fixture and the Pan and Tilt rotation limits in degrees;
- the image by which the fixture is recognized in the library.
The type is chosen before placement — with the fixture selection button on the toolbar of the Mapping window (see Adding Splines and Fixtures) — or changed afterwards: select the fixtures, click Fixture Type in Properties and choose another one from the library that opens. The new type is applied immediately to all selected fixtures. If the new type has more or fewer channels, the addresses on the port need to be recalculated: with Auto-patching enabled this happens automatically, otherwise the addresses are edited manually (see Fixture Patching).
In a new project, the RGB type is selected by default: three channels, "Pixel" kind.
The library itself can also be opened separately — menu Settings → Fixture Library. The fixtures in it are arranged into sections: LED Fixtures — standard pixel fixtures, Manufacturers — ready-made descriptions of real models, My Fixtures — the ones you created, Used in Project — the ones already placed in the current project.
Standard LED Fixtures
The LED Fixtures section consists of three groups — LED Pixels, LED Wallwasher and LED Spotlight. The channel sets in them are identical, only the kind differs: "Pixel", "Linear" and "Spotlight" respectively. Inside each group there are:
| Type | Channels | What Goes to the White Channel | When to Choose It |
|---|---|---|---|
| RGB | 3: red, green, blue | — | Regular RGB strips, lines and pixels |
| RGBW-min | 4: R, G, B, white | The smallest of the three color components | Fixtures with a separate white LED: white is added to the color, the color channels stay unchanged |
| RGBW-average | 4: R, G, B, white | The average of the three components | When white should light up under any color, not only one close to white: even a saturated blue will mix in a bit of white |
| RGBW-default | 4: R, G, B, white | The smallest of the components, and it is also subtracted from the color channels | Fixtures whose white LED replaces the gray part of the color: the color comes out cleaner, and the total brightness isn't pushed up |
| RGBW-none | 4: R, G, B and one unused channel | Nothing, the channel stays empty | A four-channel fixture whose white isn't needed or is controlled separately |
| W-average | 1: white | The average of the three color components | Single-color white fixtures: brightness is taken from the brightness of the image |
| W-min | 1: white | The smallest of the components | Single-color white fixtures, when it should only light up on the white areas of the image |
If you're not sure what to pick for an RGBW fixture, start with RGBW-min and look at the object: if there turns out to be too much white, try RGBW-default; if the fixture is too dim instead, try RGBW-average.
Manufacturer Fixtures
The Manufacturers section holds ready-made descriptions of real models: linear washes, spotlights, pixel lines, as well as moving fixtures with a dozen or more channels, where besides color there are Pan, Tilt, gobo, shutter, focus, zoom and service channels. Such descriptions are convenient because the channels in them are arranged in the same order as in the fixture itself: you just need to pick the model.
A single model in the library can have several descriptions — one for each DMX mode (Mode). Choose the one that matches the mode set on the fixture itself, otherwise the channels will be misaligned.
If the model you need isn't in the library, its description can be made in a few minutes — see Creating Custom Fixtures.
Channels
A channel is a single number from 0 to 255 that is sent to the fixture. However many channels a type has, that's how many DMX addresses one fixture will occupy.
Channels can be:
- Color
- red, green, blue — the red, green and blue components of the color. The program takes them directly from what is drawn on the Mapping field at the fixture's point.
- White
- white min and white average — a white channel calculated from the color: the smallest or the average of the three components.
- Color Minus White
- red-min(rgb), green-min(rgb), blue-min(rgb) — color channels with the white component subtracted. They work together with the white channel in RGBW-default-kind fixtures.
- Mechanics and Optics
- pan, tilt and their fine variants pan fine, tilt fine, as well as gobo, shutter, strobe, focus, zoom, frost, movement speed, reset. Found on moving and "smart" fixtures.
- Other and Empty
- Channels whose purpose isn't specified in the description, and unused channels. The program doesn't write anything to them.
The program fills the color and white channels itself, frame by frame. Their overall output can be dimmed for the whole composition at once — with the R, G, B and W sliders in its properties (see Composition Settings); for example, set W to zero to temporarily turn off the white LEDs.
The other channels hold the default value set in the fixture's description until an effect changes them. There are dedicated effects for this: Set Channel Values and Channel Animation set any channel to the needed value, PAN TILT Animation rotates moving fixtures. They are placed on the timeline like regular effects — see Adding an Effect to a Composition.
Address and Universe
Data is sent to fixtures in batches of 512 channels — such a batch is called a universe. A fixture's address is the number of its first channel within the universe, from 1 to 512; the fixture's remaining channels follow it in sequence. The pair "universe + address" uniquely determines where the fixture gets its data from, and it must match what is set on the fixture itself or on the line's controller.
The address and universe are shown in the Properties of the selected fixture — the Address and Universe parameters, and they can be changed there as well. For a spline, this is the address and universe of its first fixture; the rest are calculated from it automatically.
How many fixtures fit into one universe depends only on the number of channels:
| Fixture Channels | Fixtures per Universe | Example |
|---|---|---|
| 1 | 512 | Single-color white fixtures |
| 3 | 170 | RGB pixels and strips |
| 4 | 128 | RGBW pixels and strips |
| 15 | 34 | A medium-sized moving fixture |
When fixtures stop fitting, the program continues addressing from the next universe — a long spline can easily span two, three or more universes in a row. The device port then behaves differently depending on the mode: on SPI ports, a fixture that doesn't fit entirely before the end of the universe is moved to the start of the next one, and the last few channels of the universe are left unused; on DMX ports, addresses run as a continuous stream.
Two more parameters affect addressing:
- Address Offset
- How many channels to skip between neighboring fixtures of a spline. Usually 0 — addresses run back-to-back. A value greater than zero is needed when part of a fixture's channels are unused or controlled separately.
- Auto-patching
- While it's enabled, the program assigns addresses in order by itself and recalculates them whenever something changes inside the port. With auto-patching disabled, addresses are set manually and stay exactly as you set them.
Universes aren't pulled out of thin air for fixtures: their range is determined by the port of the device the fixture is patched to. A device has a Start Universe and Universes per Port set on it, and ports get their universes in sequence, starting from the start universe. Until a fixture is patched, its address and universe aren't tied to any output. For more on devices, ports and patching, see Fixture Patching and Light Stream Converter Parameters.
The total number of universes in a project is limited by the license: if there are more universes than allowed, the program will warn about it right on the Mapping field, and no DMX data will be sent.
Viewing Addresses on the Mapping
Addresses are labeled right next to the fixtures on the Mapping field: the labels appear when the zoom is large enough and hide when you zoom out too far. What exactly is shown is set in the menu View → 2D Mapping:
- Show Fixture Universes — the universe number is shown next to the address;
- Show Pixel Numbers — the sequence numbers of the fixtures; useful for checking the direction and order of pixels on a spline;
- Show Fixture Multi-Addresses — continuous channel numbering within the port: for fixtures in the port's second universe the addresses continue from 513, in the third from 1025, and so on. This way the addresses in the program match the numbering used by controllers that count the port's channels in sequence.
The label size is set in the program settings: Settings → Properties, section Mapping, parameter Fixture Address Size.
Frequently Asked Questions
- The fixture lights up the wrong color: green instead of red. The fixture's color order doesn't match the channel order in the type. For SPI lines the color order is set by choosing the chip in the converter settings; for DMX fixtures, choose a description with the needed channel order or create your own.
- The white LED doesn't turn on. The RGBW-none type is selected, in which the fourth channel is unused, or the W slider in the composition properties is set to zero.
- Too much white, colors look washed out. Try RGBW-default: the white component will be subtracted from the color channels.
- The fixture took up more channels than expected. Check the number of channels of the selected type: for manufacturer models it's determined by the DMX mode, and different modes of the same model take up a different number of channels.
- After changing the type, the fixtures' addresses overlapped one another. Turn on Auto-patching or recalculate the addresses on the port manually: fixtures with overlapping addresses are highlighted as errors in the Fixtures window.
- In 3D the fixture lights up as a dot but should wash a wall. Change the Fixture Beam Type in the fixture's properties in the 3D scene, or choose a type from the LED Wallwasher or LED Spotlight group.