Fixtures and patch¶

The problem¶

On a simple DMX desk, the address is the light. Fader 37 controls whatever is plugged in at address 37. That ties everything you program to the cabling:

• The rig gets re-addressed for a new venue, and every scene now drives the wrong channels.
• A moving light is hung upside down this time, so every position you programmed points at the floor.
• A spot is replaced by a different model with a different channel layout, and none of your stored values mean anything to it.

The patch is grandMA2's way of separating what you program from how it's wired.

The idea: program the fixture, not the address¶

When you patch, you tell the console three things about each device:

1. What it is: its fixture type, which says how many DMX channels it uses and what each one means (dimmer, pan, colour wheel …).
2. Which number you'll call it by: its ID.
3. Where it's connected: its DMX address, written as universe.address, for example 2.1 for address 1 in universe 2.

Everything you program, whether cues, presets or groups, refers to the fixture by its ID, never by its DMX address. The address is just the last step, where the console turns attribute values into DMX. That's why you can re-patch a fixture to a new address, even live during a show, and the show still works.

The manual says the same about IDs: change a fixture's ID numbers later and "you will not lose any programmed information."

Fixture types: a copy of the library inside your show¶

The console comes with a large library of fixture types. When you add a fixture, its type is copied from the library into the show file. You can change that copy without touching the library, and export it back if you need it in another show.

Two fixture-type details trip people up:

Mode

Many fixtures have several DMX modes (e.g. a basic 16-channel mode and an extended 30-channel mode). The mode in the console has to match the mode set on the fixture itself, or the channels don't line up.

Instances

Some fixtures consist of several separately controllable parts, such as a LED bar with six cells, or a moving head with two colour systems. Each part is an instance you can select on its own, while the fixture still has one ID.

Inside a fixture type, functions are attributes, organised as preset type → feature → attribute (for example Gobo → Gobo wheel 1 → gobo select). One attribute is one parameter, however many DMX channels it uses. See How grandMA2 thinks.

Channel ID and Fixture ID: two numbering systems¶

Every device can have a Channel ID, a Fixture ID, or both. Each number must be unique within its kind, but channel 1 and fixture 1 can be two different devices.

• Devices with a Channel ID appear in the channel sheet.
• Devices with a Fixture ID appear in the fixture sheet.
• A device needs at least one ID to be selectable at all.

Why two? Different lighting traditions number lights differently. Theatre desks have always thought in "channels" (channel 1 to 120 for the dimmers), while moving lights are usually called fixtures. grandMA2 lets you keep both habits in one show, for example dimmers as channels 1 to 48 and moving lights as fixtures 101 to 112.

Fixing the rig in the patch, not in the programming¶

Several patch options exist so that a rig that differs from the plan can be corrected once, in the patch, rather than in every cue:

Pan/Tilt DMX invert

The fixture is hung the other way round. Invert the axis and positions point the right way again.

Pan/Tilt encoder invert

Makes the encoder direction match the real movement, so turning the pan encoder right moves the beam right from where you stand.

Pan/Tilt offset

The manual puts it directly: useful "if the show has been preprogrammed or it is a touring show, and the fixtures are not hung the way they were planned to be." The offset is added on output. You see it in the DMX sheet, not in the fixture sheet.

Multipatch

Two (or more) physical lights that should always do exactly the same, for example a pair of pars left and right of the stage. They share one ID; each extra unit just gets its own DMX address. Multipatched fixtures cost no extra parameters, but you can't program them individually.

DMX breaks

The opposite case: one logical fixture made of several separately addressed devices, such as a moving head with its lamp on an external dimmer, or a fresnel with a colour scroller. Up to 8 breaks give it several start addresses but one ID.

When the dimmer curve doesn't match the look¶

A cue fades the dimmer from 0 to 100% over 8 bars of a build-up, the console counts up evenly, and the light doesn't. A typical LED wash jumps to "clearly on" in the first few percent and then barely changes for the rest of the fade, so the build-up has arrived long before the drop. Or two fixture types side by side at 30% look nothing alike: one is glowing, the other is almost at full.

The console's fade is linear in values; what you see depends on how the fixture turns DMX into light. You can fix that in three places, from the fixture outwards:

1. In the fixture. Many LED fixtures have a dimmer curve setting (linear, square, inverse square, S-curve) and often a dimmer speed or smoothing mode, either in the fixture's own menu or on a control channel. This is the first thing to try, because the fixture knows its own LEDs best.
2. In the fixture mode. A mode with a 16-bit dimmer (dimmer fine) gives much smoother fades at the low end, where 8-bit steps are visible.
3. In grandMA2's patch, with a DMX profile. A DMX profile is a curve you draw in the graph editor (or load from the predefined graphs). It maps the console's value to the DMX value that goes out. You can assign it to the dimmer attribute in the fixture type, so every fixture of that type uses it, or to single DMX addresses in the DMX parameter list. Like the offsets above, it acts on output: your cues and presets keep their values, and you can change or remove the curve later without touching any programming.

The graph editor is the same one you use for effect forms, so the same idea works for intensity effects: the shape of the form decides how a pulse feels, not only its speed (see Effects and chasers). Cues get the same editor too: a fade path shapes one cue's fade (see Fade paths). The profile fixes the fixture; the fade path shapes a single transition.

Edit setup vs. live patch¶

There are two ways into the patch:

• Patch & Fixture Schedule (EditSetup) can change everything, including the structure (adding fixtures, changing types). When you leave it, the show is re-uploaded to all connected devices, and DMX output stops while that happens.
• Patch Only (Live) only allows changes that don't touch the structure, such as DMX addresses and offsets, and doesn't interrupt output.

So: build the rig in EditSetup before the show. During a show or a focus session, use live patching. Layers in the fixture schedule are only for organising your patch list (by type or position, say). Moving fixtures between layers doesn't affect programming.

When it matters, and when not¶

• A fixed hobby rig that never moves: you set the patch up once. The important parts are picking the right fixture type and mode, and the Channel/Fixture ID decision.
• Anything that travels or gets rehung: offsets, inverts and live patch are what keep your programming usable.
• Mixed LED fixtures, or fades that don't feel right: check the fixtures' own dimmer curve settings, then use DMX profiles.
• Skip at first: DMX breaks, instances in depth, building your own fixture types. Only needed when a fixture forces you to.

Related¶

• How grandMA2 thinks: attributes vs. DMX channels
• Presets: the other half of "survive a changed rig"
• Moving heads: orientation, Flip, the 3D stage, XYZ and layouts
• Reference: Adding fixtures to the show, Live patching, Multipatching, DMX sheet, DMX profiles

Sources¶

• What are channels & fixtures: Channel ID / Fixture ID, default keyword, IDs can change without losing programming
• What are attributes
• Adding fixtures to the show: library copy, mode, instances, DMX address format, invert and offset options
• Multipatching
• What are DMX breaks
• DMX profiles: graph editor, predefined graphs, percent readout
• DMX parameter list: profile per DMX address
• Anatomy of fixture types: profile per attribute
• Create effect forms: the same graph editor
• Working with layers
• Live patching: show upload stops DMX