Flux Lights and Capture over Art-Net, step by step

There is a separate article about consoles and visualisers in general: addressing, loopback, two machines, the off-by-one in universe numbers. This one is about the specific pair with Capture, because Capture receives data its own way — and the classic "nothing shows up" is fixed here differently than in other programs.

The difference is this. Capture does not make you set up reception by hand: external universes it sees on the network are picked up and linked to the universes of your project automatically. That is convenient, and that is exactly what confuses people — there is nothing to "enable", and still no picture. In exchange Capture gives you something most programs do not: it shows which external universes actually reached it. That is the main diagnostic tool, and this article is built around it.

Step 1: the output in Flux Lights

Settings → Network output → add an Art-Net output.

• Node IP. Both programs on one machine — 127.0.0.1. Two machines — the address of the one running Capture. We send unicast: the packet goes to that address and nowhere else.
• Universe range. The first and the last console universe you want to send. Only active universes go out — the ones that have a patch or values.
• Base. The device universe the range starts from. For Art-Net the default is 0, and that is the right value: Art-Net numbers universes from zero while the console shows them from one. With base 0, console universe 1 leaves as Art-Net universe 0.

The refresh rate lives in the same card — 40 Hz by default, the same rate that goes to USB. There is no need to lower it for a visualiser: the loopback interface does not notice twenty universes at 40 Hz.

Step 2: Capture

From the official Capture reference manual (the Universes tab sections of the 2022–2026 versions agree in substance and differ only in wording):

• The Universes list holds the universes of the project — the ones your fixtures are patched to inside the venue model.
• External universes discovered on the network are linked to them automatically.
• The External universe property lets you override that link manually and, more importantly, shows which external universes Capture is seeing.

There is no separate "enable Art-Net" switch to forget in this scheme. If packets arrive, universes appear.

Step 3: test before you program

Half a minute that saves an evening.

Bring one fixture up: dimmer at full, shutter open if the profile has one. Look at the Capture screen.

• Something lit up — the whole chain works, and from here everything depends on your patch and your cues.
• Nothing — go down the list below, and do not start programming until you have sorted it out. A finished show nobody ever watched is the most expensive kind of wasted work.
• The wrong fixture lit up — the chain works, but the patch in the console and the patch in the venue model disagree. That is the second most common cause after universe numbering.

When it is empty: which side is silent

The job is not to guess but to split the chain in two: did anything at all reach Capture?

Capture shows no external universes at all. Packets are not getting there, so the transport is to blame. Three places:

1. Address. We unicast to exactly the IP you typed. On one machine that is 127.0.0.1; on two, it is the address of the Capture machine's interface that faces your network, not the Wi-Fi next to it.
2. Firewall. Windows asks about network access on first launch, and a refusal is remembered. Art-Net lives on UDP port 6454.
3. Subnet. Both machines must share one. The Art-Net classic is 2.0.0.1 and 2.0.0.2 with mask 255.0.0.0; 10.x.x.x works the same way. Turn DHCP off on that interface: the address will change on exactly the day you least want to think about it.

Capture sees an external universe but the fixtures stay dark. Transport is fine, numbering is not. Look at External universe: it tells you which external universe arrived. If the console sends its 1..4 with base 0, what goes out is 0..3 — and those have to be linked to the project universes your fixtures sit on. The practical rule: shift the base by one in either direction and look again. In the vast majority of cases that was the whole problem.

The console shows packets leaving. Each output has a counter of sent packets and errors. Counter rising and Capture empty — the problem is between the machines, not in the console. Counter frozen — the universe is inactive: no patch, no values, nothing to send.

The "Find" button in the "Art-Net nodes on the network" block. It sits in the same settings card, below the list of outputs, and lists the nodes that answered an ArtPoll. Whether Capture answers ArtPoll we have not verified, so an empty list proves nothing here: output does not depend on the poll and works whether or not a node introduced itself.

Worth knowing in advance

Blind data. Capture has a property that governs how "blind" sACN and CITP data is treated. If you work blind on a console that supports it and the picture surprises you, that property may be the reason. Flux Lights never sends blind levels to the network: what goes to the network is what goes to USB — the output after master and blackout.

Blackout is visible. Master and blackout are applied before sending, so a blacked-out console gives a black picture. That makes a handy liveness test: press BLACKOUT and Capture goes dark, which means data is flowing right now rather than stuck on the last frame.

Broadcast is not needed. It works, and it is sometimes the fastest way to answer "does anything arrive at all", but it buries the whole network in packets — dozens of universes at forty frames a second reach every device on the wire. For a console-plus-Capture pair, unicast is both more precise and quieter.

What to check at the venue

The desk setup and the venue setup are different schemes, and the move breaks exactly two things.

• Real nodes use a different universe base. At home you fed Capture with base 0; the node on the truss has its own numbering, and you read it in the node's own settings. The visualiser output is a separate row in the list — you can simply switch it off and keep it until the next rehearsal.
• Every position will need fixing. The angles in a venue model are a model: the truss ends up lower, the fixture hangs at another tilt, the beam aimed at the singer lands on the drums. A visualiser checks the logic of the show, not the focus, and that is fine: there is neither time nor gear to build the logic in the room, and focusing without the room is impossible in principle.

The limits of this text

The Flux Lights steps are verified against our own output. Capture's behaviour is described from its official manual rather than from an installation of ours: field names and placement differ slightly between the 2022–2026 versions, so if yours calls something else — look for the list of project universes and the external universe property next to it. The mechanics are the same.