Fixtures and patching
What a fixture is in Spectralite, and how patching gives it a DMX address.
A fixture is any device Spectralite controls over DMX, such as a moving head, an LED bar, a par can, or a strip of pixels. The word covers two things. One is the type of device: a reusable description of how that model of light behaves. The other is the specific unit in your rig at a specific address. Spectralite models them separately, and patching turns the first into the second.
Definitions and patched fixtures
A fixture definition is the reusable type. It describes one model of light without giving it an address. A definition comes from the built-in library, from a file you import, or from one you author yourself. You can patch the same definition many times, so eight identical bars share one definition and differ only in address.
A definition holds one or more modes. A mode is a selectable DMX personality: the channel layout the fixture uses in that operating mode. A basic RGB mode might occupy three channels. A full-feature mode of the same light might occupy twenty, with pan, tilt, gobo, and finer color control added. You pick the mode when you patch. It must match the mode set on the physical fixture, or the channels will not line up.
Inside a mode, Spectralite distinguishes two kinds of internal structure. A sub-fixture is a physically independent, separately positionable unit within one device. For example, each of the eight strips of an eight-strip bar is a sub-fixture that you want to place in space on its own.
A pixel is a single addressable emitter point. It is the smallest thing the engine drives color onto. A single-cell par is one pixel, and a matrix panel is a grid of pixels. Most library fixtures are one sub-fixture that contains all the pixels the hardware exposes. You need more than one sub-fixture only for hardware with physically separate parts.
Each pixel carries emitter roles: the colored light sources the fixture mixes. Red, green, and blue are the familiar three, but real fixtures add white, amber, lime, warm and cool whites, and more. A definition imported with measured color data also records where each of those emitters sits as a real color. These positions are its primaries, and together they bound the range of color the fixture can physically produce.
You do not work with that data directly. The color engine reads it so that one authored color renders correctly onto each fixture's own emitters. Color explains how, and Importing GDTF explains where the measured data comes from.
A patched fixture is a definition placed into your project with an address. It references a definition, fixes a mode, and adds the two numbers that locate it on the wire: a universe and a start address. Patching or re-patching a fixture sets only those two numbers. The definition stays shared and unchanged.
Placing a fixture in 3D space is a separate step from patching it. An address decides which channels a fixture listens to. A fixture layout decides where it sits, so effects can sweep across your rig by geometry. You can patch a fixture without placing it, and place it without an address.
Universes and the 512-channel structure
DMX carries lighting data in fixed blocks called universes. One universe is exactly 512 channels, and a channel is a single 8-bit value from 0 to 255. A rig with more than 512 channels of control uses more universes, each an independent block of 512.
Every channel a fixture uses sits at one of the 512 slots of some universe. A dimmer channel, a pan channel, and a red channel each take one slot. When you patch a fixture, you choose the universe and the run of consecutive slots in it that the fixture claims.
Spectralite supports far more universes than any single show needs. The practical limit is how many your output hardware and network can carry. Output covers how universes leave Spectralite and reach that hardware.
How a fixture occupies channels
A patched fixture claims a contiguous range of channels starting at its address. The length of that range is the mode's channel footprint. The footprint is the total number of channels the mode uses, including every emitter, dimmer, and movement channel it drives. An eight-channel mode patched at address 100 occupies channels 100 through 107. To avoid an overlap, the next fixture must start at 108 or later.
That footprint is a property of the mode. A mode with four pixels of RGB plus a master dimmer occupies thirteen channels. When you switch a patched fixture to a different mode, its footprint changes, and the range it claims changes with it.
If a mode's footprint runs past channel 512, the fixture continues into the next universe automatically. A fixture patched near the top of a universe can straddle the boundary and occupy the tail of one universe and the head of the next. Spectralite lays out the channels across as many universes as the footprint needs, so you never split a fixture by hand.
The number you type versus the number on the wire
The universe and address you enter when you patch are 1-based. Universe 1 is the first universe, and address 1 is the first channel. This numbering matches the fixture's display and its manual. As a result, the number you dial into the physical light is the number you type into Spectralite.
On the wire, the numbering differs by protocol. Spectralite converts it, so type the numbers exactly as the fixture shows them and never pre-subtract. Output covers how patch universes map onto the numbers Art-Net and sACN carry, and when a per-output offset matters.
A third-party receiver can number its universes differently from Spectralite. A separate per-output setting aligns the two and leaves the patch alone. See Output.
Overlaps are flagged
Two fixtures must not share a channel. If they do, both write to the same slots, and the hardware sees whichever fixture's data lands last. Spectralite lets you patch into an occupied range and sends whatever addresses you give it, but it shows you the collision.
The Address Space panel maps every channel in every universe to the fixture that occupies it. It highlights any cell claimed by more than one fixture as a conflict. Scan it before a show. If no cell is flagged, no two fixtures share a channel.
An overlap is flagged, never blocked. If you patch a fixture onto channels already in use, the fixtures overlap silently until you resolve the overlap. After any bulk re-patch, check the Address Space panel.
Where fixture profiles come from
The channel layout a definition carries can come straight from the manufacturer. GDTF is the open interchange format for fixture profiles. A GDTF profile packages a fixture's real DMX modes. When the manufacturer measured them, the profile also holds the emitter chromaticities and response curves.
When you import a GDTF profile, you get the exact channel map the maker published. You also get the color data the engine uses to render accurately onto that fixture's emitters. Importing GDTF covers how to import a profile and what calibration data it can carry.
Related
Add a fixture
Bring a fixture definition into your project from the library or a file.
Patch a fixture
Set the universe, address, and mode for a fixture in your rig.
The Fixtures panel
Manage every patched fixture in the current project.
Color
Author one color and let the engine render it onto each fixture's real emitters.
Output
How universes leave Spectralite and reach your hardware.
Core concepts
The ideas the rest of the docs build on.