Splines and Single Fixtures

Every fixture in a Light Stream project belongs to one of two kinds: it is either a single fixture or a spline — a line along which a chain of fixtures is arranged. This choice determines how the fixtures are addressed, how they are patched, and how easy it will be to change the layout later. Below is how they differ, what to choose for a specific object, and how to convert one into the other if the choice turns out to be wrong.

How both are drawn is covered in the article Adding Splines and Fixtures. Which fixture types exist and how many channels they have is covered in the article Виды и типы приборов.

Brief overview of the difference

Single fixture: A standalone object: its own name, its own address, its own universe, its own fixture type. In the Fixtures window it occupies a separate row, and on the Mapping field it looks like a dot. It can be moved, addressed, and patched independently of its neighbors.

Spline: A line with fixtures arranged along it. A spline is a single object: one name, one starting address, one fixture type for all the fixtures on the line. The program arranges the fixtures along the line itself and assigns them sequential addresses itself. In the Fixtures window a spline occupies a single row, no matter how many fixtures are on it — whether 10 or 500.

The main practical consequence: a spline is managed as a whole, while single fixtures are managed one by one.

	Single Fixtures	Spline
In the Fixtures window	one row per fixture	one row for the entire line
Address	set for each fixture	set for the first, the rest are calculated automatically
Patching	each fixture is moved to a port individually	moved to a port as a whole, in one move
Number of fixtures	changed by adding and removing fixtures	the Fixture Count parameter in the properties
Layout	arbitrary: wherever it was placed, there it stays	along a line, whose shape is edited via its vertices
Fixture order	set by their addresses	set by the direction of the line, flipped with the Reverse button
Selection on the field	a single fixture can be selected	the entire line is selected as a whole
Link to 3D	with a single fixture in the 3D View window	with a spline in the 3D View window

For effects there is no difference: both the fixtures of a spline and single fixtures receive color based on their position on the Mapping field. The fixture kind is chosen for convenience when working with the project and with addressing, not for the picture.

How to tell them apart on the Mapping field

Fixtures of both kinds are drawn as green dots; selected ones are red.
The fixtures of a spline are connected by a dark gray line. It is there only for clarity — the fixtures produce light, not the line. Showing the lines is toggled with the menu item View → 2D Mapping → Show Splines and is enabled by default.
The first fixture of a spline is outlined with a white frame. This is the start of the line: addressing counts from it, and it is the one the Reverse button swaps with the last one.
If the fixtures are not labeled, enable what you need in the same menu: Show Pixel Numbers, Show Fixture Universes, Show Fixture Multi-Addresses. The Show Pixel Grid item turns on the field's grid — it's convenient for checking whether the fixtures are lined up evenly.

You can check for certain in the Properties window: a spline has the parameters Fixture Count, Smooth, and Distribution Type there, while a single fixture does not.

What to choose for a specific object

Spline — when fixtures run in sequence along a single line and are addressed sequentially:

LED strips, bars, pixel tubes;
garlands and strings;
facade outlines, cornices, window openings, railings;
any long row of identical fixtures connected to a single port.

Single fixtures — when each fixture stands on its own:

spotlights, floodlight fixtures, beam fixtures;
individual points on the object, placed without a common order;
fixtures of different types mixed together;
fixtures that need non-sequential addresses or different ports.

A matrix is usually built from splines: you draw one row, give it the required fixture count, and get the remaining rows with the Duplicate tool — it makes copies with a constant step in coordinates, addresses, and universes.

General rule of thumb: the longer the row of identical fixtures on a single line, the more advantageous a spline is. Five hundred individually placed fixtures means five hundred rows in the Fixtures window and five hundred addresses that have to be tracked manually; the same row as a spline is one row, one address, and one count parameter.

Addressing

This is the most noticeable difference between the two kinds, and it is the reason the layout most often has to be redone.

For a spline

The properties specify Address and Universe — they apply to the first fixture on the line. After that the program calculates the rest itself:

the step between fixtures equals the number of channels of the selected fixture type plus the value of the Address Offset parameter (0 by default, meaning the addresses run back to back);
once the fixtures no longer fit in a universe, the rest of the spline automatically moves to the next one; on a port switched to SPI mode, a fixture is not split in this case — the next fixture starts at the first address of the next universe;
in the Fixtures window, the occupied range is shown next to the spline as U1-1-300: universe, first and last address.

Any change — fixture count, fixture type, address offset, reverse — recalculates the addressing of the whole line at once. Addresses are not set manually for fixtures inside a spline: that is the price of convenience.

For single fixtures

Address and universe are set for each fixture individually. To avoid doing this manually, fixtures are placed with Auto Patching enabled — then each next fixture receives the address right after the previous one. Addresses can be recalculated for fixtures that are already placed: right-click a port in the Fixtures window → Recalculate Fixture Addresses.

Keep in mind: the value entered in the Address field of the Properties window is applied to all fixtures currently selected in the Fixtures window. If you need to fix the address of a single fixture, deselect the rest.

For details on patching and distributing fixtures across ports, see the article Патчинг приборов.

Addressing errors

If fixtures or splines go beyond the universes allotted to the port, or their addresses overlap each other, the row in the Fixtures window turns red — and so does the port along with it. A red row means the signal will not reach those fixtures: fix the addresses, the fixture count on the spline, or the number of universes per port.

Properties

Some parameters exist for both kinds, some only for a spline.

Parameter	Single Fixture	Spline	What it does
Name	yes	yes	Name in the Fixtures window. Clear names save a lot of time when patching.
Visibility	yes	yes	A disabled fixture is not displayed on the field and cannot be selected with the mouse; the linked object in the 3D View is hidden along with it.
Address, Universe	yes	yes	For a spline — the address and universe of the first fixture on the line.
Fixture Type	yes	yes	A button with the current fixture's name, opens the Fixture Library. For a spline, the type is changed for all fixtures on the line at once.
Go to 3D Fixture	yes	yes	Finds and selects the linked object in the 3D View window.
Distribution Type	—	yes	Uniform — the fixtures are spread along the entire length of the line, and you set their number. Fixed Pixels — a fixture is placed at every vertex of the line, and the fixture count equals the number of vertices.
Fixture Count	—	yes	How many fixtures are on the line. Available with uniform distribution.
Address Offset	—	yes	How many channels to skip between neighboring fixtures on the line.
Reverse	—	yes	Flips the fixture order: the first one becomes the last.
Smooth	—	yes	Rounds the corners of the line: instead of a polyline you get a smooth curve.
Snap to Pixels	—	yes	Places the line's fixtures exactly on the pixel grid cells.

Spline properties are applied to all selected splines at once. This is convenient when you need to set identical settings for a dozen identical bars: select all of them and enter the value once.

Converting one kind into the other

The choice is not final. The toolbar of the Mapping window has two buttons — Convert to Spline and Convert to Fixtures (in earlier versions they were called Link and Unlink). Both work with the Select and Move tool active, and both can be undone with Ctrl+Z. The buttons are locked while in spline edit mode.

From single fixtures to a spline

Take the Select and Move tool and select two or more single fixtures.
Click Convert to Spline.

What you get:

the line will pass through the positions of the selected fixtures, one fixture per vertex — the new spline is assigned the Fixed Pixels distribution type;
the order of the vertices is determined by addresses, not by the order of selection: the line is built from the fixture with the lowest address to the one with the highest;
the address, universe, fixture type, and port are taken from the first fixture — for the rest they will be reassigned to match the line's common numbering;
snap to pixels is disabled for the new spline, so the fixtures stay exactly where they were;
the original single fixtures are removed from the project, and the new spline ends up selected right away.

Before converting, it is worth checking the addresses: if they are not arranged in the same order the fixtures follow on the object, the line will come out tangled. It is simpler to patch the fixtures in order first and only then assemble them into a spline.

The button is disabled if only one fixture is selected, if a spline is among the selection, or if spline edit mode is on.

From a spline to single fixtures

Select one or more splines.
Click Convert to Fixtures.

Each fixture on the line becomes independent: it stays in place, keeps its address and universe, and ends up on the same port the spline was on; within the port the fixtures are arranged in ascending order of address. The line itself disappears along with its parameters — smoothing, reverse, fixture count, and distribution type.

Conversion is needed when:

part of the line's fixtures need to be moved to a different port or a different converter;
the fixtures need non-sequential addresses;
individual fixtures need to be deleted or moved, rather than the whole line.

After converting, check the link to the 3D View window: it was created for the spline, and the new single fixtures will need to have it assigned again. See the article Связь 2D и 3D for that.

Frequently asked questions

The fixture count on the spline won't change. The Fixed Pixels distribution type is selected — in it the fixture count equals the number of vertices on the line. Switch to Uniform or add vertices in spline edit mode.
How do I select a single fixture inside a spline? You can't: a spline is selected, addressed, and moved only as a whole. If you need access to individual fixtures, convert the spline to fixtures.
The animation runs along the line in the wrong direction. For a spline, click Reverse; for single fixtures, check the order of the addresses.
The "Convert to Spline" button is disabled. You need to select at least two single fixtures and exit spline edit mode.
A fixture's or spline's row in the "Fixtures" window has turned red. The addresses have gone beyond the port's universes or overlap with a neighbor's addresses.
The fixtures on the spline are not aligned to the grid cells. Enable Snap to Pixels in its properties.
There are too many fixtures, and it's impossible to find anything in the list. Combine rows of identical fixtures into splines: instead of hundreds of rows in the Fixtures window, there will be just one per line, and addresses will be calculated automatically.