Splines and Single Fixtures

Every fixture in a Light Stream project is one of two kinds: 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 their layout later. Below is how they differ, what to choose for a particular 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. What fixture types exist and how many channels they have is covered in the article Виды и типы приборов.

The Difference in Short

Single Fixture: An independent 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 point. 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 consecutive 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 at a time.

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

For effects there is no difference: both the fixtures on a spline and single fixtures get their 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 itself.

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 emit 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 in white. 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 aren't 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, which is handy for checking whether the fixtures are lined up evenly.

In the Fixtures window a spline and a single fixture are distinguished by the icon to the left of the name: for a spline it's a polyline, for a single fixture it's the fixture itself. You can be certain by checking the Properties window: a spline has the Fixture Count, Smooth, and Distribution Type parameters there, while a single fixture doesn't.

What to Choose for a Particular Object

Spline — when fixtures run in a row along a single line and are addressed consecutively:

LED strips, bars, pixel tubes;
garlands and strings of lights;
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, floodlights, beam fixtures;
individual points on an object placed without a common pattern;
fixtures of different types mixed together;
fixtures that need non-sequential addresses or different ports.

A matrix is usually built out of splines: you draw one row, give it the needed fixture count, and get the remaining rows with the Duplicate tool — it makes a given number of copies with a constant X and Y offset and a constant address offset.

General rule of thumb: the longer the row of identical fixtures on a single line, the more it pays off to use a spline. Five hundred separately 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's the reason a layout most often needs to be redone.

For a Spline

The properties set the Address and Universe — these apply to the first fixture on the line. From there the program calculates everything 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);
when the fixtures stop fitting into a universe, the rest of the spline automatically moves on to the next one; on a port switched to SPI mode a fixture is never split — the next fixture simply starts at the first address of the next universe;
in the Fixtures window, next to the spline, the occupied range is shown as U1-1-300: the port's starting universe, the first address, and the last address.

Any change — the fixture count, the fixture type, the address offset, a reverse — recalculates the addressing of the whole line at once. Fixtures inside a spline are never addressed manually: that's the price of the convenience.

For Single Fixtures

The address and universe are set for each fixture individually. To avoid doing this by hand, fixtures are placed with Auto-patching enabled — then each next fixture gets the address right after the previous one. Addresses for fixtures already placed can be recalculated: right-click the port in the Fixtures window → Recalculate Fixture Addresses.

Keep in mind: the value entered into 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 just one fixture, deselect the rest.

For details on patching and distributing fixtures across ports, see the article Patching Fixtures.

Addressing Errors

If fixtures or splines go beyond the universes allocated to a port, or their addresses overlap, the row in the Fixtures window is colored red — and so is the port itself, along with it. A red row means the signal won't reach these 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	The 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 showing the current fixture's name; opens the Fixture Library. For a spline, changing the type changes it for every fixture on the line at once.
Go to 3D Fixture	yes	yes	Finds and selects the linked object in the 3D View window. If there are several linked objects, the program offers to pick the one you need from a list.
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. Only changes with uniform distribution; with fixed pixels the field shows the number of vertices, and the entered value has no effect.
Address Offset	—	yes	How many channels to skip between adjacent fixtures on the line.
Reverse	—	yes	Flips the order of the fixtures: the first one becomes the last.
Smooth	—	yes	Rounds off the corners of the line: instead of a polyline you get a smooth curve.
Snap to Pixels	—	yes	Places the fixtures of the line exactly onto the cells of the pixel grid.

A spline's properties are applied to every selected spline at once. This is handy when you need to set identical settings for a dozen identical bars: select them all and enter the value once.

Converting One Kind Into the Other

The choice isn't 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). The selection for them is usually made with the Selection and Movement tool; both buttons are disabled while in spline edit mode. Any conversion can be undone with Ctrl+Z.

From Single Fixtures to a Spline

Take the Selection and Movement tool and select two or more single fixtures.
Click Convert to Spline.

What you get:

the line passes 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 the addresses, not by the selection order: the line is built from the fixture with the lowest address to the fixture 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 shared numbering;
snap to pixels is off 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 is selected right away.

Before converting, it's worth checking the addresses: if they aren't set in the same order the fixtures follow on the object, the line will come out tangled. It's easier to patch the fixtures in order first and only then combine 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 active.

From a Spline to Single Fixtures

Select one or more splines.
Click Convert to Fixtures.

Every 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, and their names are derived from the fixture type with sequential numbers. The line itself disappears along with its parameters — smoothing, reverse, fixture count, and distribution type.

The conversion is useful when:

part of the line's fixtures need to be moved to another port or another converter;
the fixtures need non-sequential addresses;
you need to delete or move individual fixtures 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 it assigned again. See the article Linking 2D and 3D for that.

Frequently Asked Questions

The fixture count on the spline won't change. The Fixed Pixels distribution type is selected — with 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.
The row of a fixture or spline in the \"Fixtures\" window has turned red. The addresses went beyond the port's universes or overlapped with a neighbor's addresses.
The fixtures on the spline aren't 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 the addresses will be calculated automatically.