Fixture Kinds and Types
A fixture in Light Stream is whatever the program controls at the output: a single LED on a strip, a pixel on a bar, a linear wash on a façade, or a full 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 determines the picture in the preview, the type determines the data sent to the real equipment.
Both the kind and the type are set by a single choice: the fixture selected from the Fixture Library. Below is how the kinds differ from each other, which types are available in the library, what channels are, and how addresses and universes are built from them.
Three Fixture Kinds
| Kind | How it lights | What it's for | Beam parameters |
|---|---|---|---|
| Pixel | Glows on its own, like a point; no beam | Strips, bars, pixel screens, string lights — anything made of individual LEDs | No separate beam parameters: the fixture in the scene has Pixel Width, Pixel Height, and Pixel Length set |
| Linear | Washes a surface with a wide beam along the body | Linear washes, wall lighting, cornices, window reveals | Length, Angle, Depth |
| Spotlight | Produces a directed cone of light | Spotlights, narrow-beam architectural fixtures, moving fixtures | Angle, Height |
The kind only affects 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 on the DMX data at all. Choose it based on how the fixture actually lights in real life: that determines how closely the preview will match 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 configured there as well. The set of fields depends on the selected kind: for a linear fixture these are Length, Angle, and Depth; for a spotlight — Angle and Height; a pixel has no beam dimensions at all.
What the Fixture Type Defines
The type is a fixture description 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 the fixture 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 afterward: 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 in the port need to be recalculated: with Auto-patching enabled this happens automatically, otherwise the addresses are corrected manually (see Patching Fixtures).
In a new project the default type is RGB: three channels, kind “Pixel”.
The library itself can also be opened separately — menu Settings → Fixture Library. Fixtures in it are organized into sections: LED Fixtures — standard pixel fixtures, Manufacturers — ready-made descriptions of real models, My Fixtures — the ones you created, Used in Project — those 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 into the white channel | When to choose |
|---|---|---|---|
| RGB | 3: red, green, blue | — | Ordinary RGB strips, bars, 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, and the color channels remain unchanged |
| RGBW-average | 4: R, G, B, white | The average of the three components | When white should light up under any color, not just colors 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, which 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 is not overdriven |
| RGBW-none | 4: R, G, B, and one unused channel | Nothing, the channel stays empty | A four-channel fixture whose white is not 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 image brightness |
| W-min | 1: white | The smallest of the components | Single-color white fixtures, when they should only light up on white areas of the image |
If you're not sure what to choose 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 instead the fixture lights too dimly — RGBW-average.
Manufacturer Fixtures
The Manufacturers section contains ready-made descriptions of real models: linear washes, spotlights, pixel bars, 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. These 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.
One 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 not line up.
The model you need isn't in the library — its description takes just a few minutes to create, see Создание пользовательских приборов.
Channels
A channel is a single number from 0 to 255 sent to the fixture. However many channels a type has, that is how many DMX addresses one fixture will occupy.
Channels are of the following kinds:
- Color
- red, green, blue — the red, green, and blue color components. 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 computed 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, and reset. Present on moving and “smart” fixtures.
- Other and empty
- Channels whose purpose is not specified in the description, and unused channels. The program does not 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 Red, Green, Blue, and White sliders in the Color Filtering section of its properties (see Composition Settings); for example, setting White to zero to temporarily turn off the white LEDs.
The other channels keep the default value set in the fixture description until an effect changes them. There are dedicated effects for this: Set Channel Values and Channel Animation set any channel to the desired value, and PAN TILT Animation rotates moving fixtures. They are placed on the timeline like ordinary effects — see Adding an Effect to a Composition.
Address and Universe
Data is sent to fixtures in chunks of 512 channels — such a chunk 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 immediately after it. The pair “universe + address” uniquely determines where the fixture gets its data from, and must match what is set on the fixture itself or on the line controller.
The address and universe are visible in the Properties of the selected fixture — the Address and Universe parameters, which can also be changed there. For a spline these are 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:
| Channels per fixture | 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 behaves differently depending on the mode: on SPI ports, a fixture that doesn't fit completely to the end of the universe is moved to the start of the next one, and a few of the last channels of the universe remain unused; on DMX ports the addresses go in a continuous stream.
Two more parameters affect addressing:
- Address Offset
- How many channels to skip between adjacent fixtures of a spline. Usually 0 — addresses run back-to-back. A value greater than zero is needed when part of the fixture's channels is unused or controlled separately.
- Auto-patching
- While it's enabled, the program assigns addresses in order by itself and recalculates them whenever something changes within the port. With auto-patching disabled, addresses are set manually and stay as you set them.
Universes aren't assigned to fixtures out of thin air: their range is determined by the device port the fixture is patched to. A device has Start Universe and Universes per Port parameters, and ports receive their universes in sequence, starting from the start universe. Until a fixture is patched, its address and universe are not tied to any output. For more on devices, ports, and patching, see Patching Fixtures 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 DMX data will not 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 disappear when zoomed far out. What exactly is shown is configured in the View → 2D Mapping menu:
- Show Fixture Universes — the universe number is displayed next to the address;
- Show Pixel Numbers — the sequential numbers of the fixtures; convenient 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 sequentially.
The label size is set in the program settings: Settings → Properties, section Mapping, parameter Fixture Address Size.
Frequently Asked Questions
- The fixture lights the wrong color: green instead of red. The fixture's color order doesn't match the channel order in the type. For SPI strips the color order and chip type are set in the converter settings; for DMX fixtures, choose a description with the correct channel order or create your own.
- The white LED doesn't turn on. Either the RGBW-none type is selected, in which the fourth channel is unused, or the White slider in the Color Filtering section of the composition properties is set to zero.
- There's too much white, the 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 channel count of the selected type: for manufacturer models it's determined by the DMX mode, and different modes of the same model occupy a different number of channels.
- After changing the type, the fixtures' addresses overlap each other. Turn on Auto-patching or recalculate the addresses in the port manually: the address and universe of each fixture are visible in the Properties window, and the address labels on the Mapping field help you quickly find the overlap.
- In 3D the fixture lights up as a point, but it should wash the 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.