QLC+ Lighting Programming Skill

Key Concepts

DMX Fundamentals

• 512 channels per universe, values 0-255
• QLC+ supports unlimited universes (4 default)
• Fixtures are patched at a universe + start address

HTP vs LTP (Critical for understanding conflicts)

Fade Out Only Affects HTP

Grand Master

• Reduce: channels reduced by percentage (50% GM = all channels at 50% of current)
• Limit: channels cannot exceed the GM value (GM at 127 = max output 127)

Blackout

Palettes (v5)

Function Types

Scene

• Selective channel control: Only enabled channels are affected. Disabled channels are NEVER touched. This enables layering.
• Fade In: Time to fade ALL channels (HTP AND LTP) to their target values. This is unique to Scenes — in other functions, Fade In only affects HTP.
• Fade Out: Time to fade HTP/intensity channels back to zero. ONLY HTP channels are affected by Fade Out — LTP channels retain their values.
• No duration: Scenes persist until stopped or overridden
• Monolithic scenes (all channels enabled) work well for chaser-driven workflows where only one scene is active at a time
• Partial scenes (only some channels) enable layering but require careful management
• Crossfade blending: When a chaser transitions between two scenes, it calls

  setBlendFunctionID

  so the new scene reads starting values from the previous scene — enabling true crossfade without snapping.

Chaser

duration = fadeIn + hold

• duration

  is the TOTAL step time, not just hold

• hold = duration - fadeIn

• The step ends when

  elapsed >= duration

• On step end,

  prevStepRoundElapsed = elapsed % duration

  carries overshoot into the next step (prevents timing drift)
• FadeOut is NOT included in duration — it overlaps with the next step or runs after stop

<Speed>

<Step>

Function::defaultSpeed()

Default

Common

duration()

• With

  SpeedModes FadeIn="Default" Duration="PerStep"

  : the step's Hold attribute IS the total step time. The child function's own FadeIn is used for crossfading. The Hold value is what contributes to the timeline.
• With

  SpeedModes FadeIn="PerStep" Duration="PerStep"

  : the step's FadeIn overrides the child function's fade. Duration = FadeIn + Hold.

elapsedBeats

<Tempo Type="Beats"/>

Function::infiniteSpeed()

if (duration != infiniteSpeed && elapsed >= duration)

Sequence

<Step Values="N">

fixtureID:channel,value,channel,value:fixtureID:channel,value,...

:

,

Collection

preRun()

m_runningChildren

• Cannot contain itself (self-containment check in

  postLoad

  )
• Duplicate function IDs are rejected
• No speed settings of its own

EFX

RGB Matrix

Show

• Multitrack view similar to a DAW — each track is bound to a Scene
• Sequences on a track can only control channels of that track's Scene
• Functions can be placed at precise time positions, dragged, copied
• Supports BPM grid (4/4, 3/4, 2/2) with snap-to-grid for music sync
• Tracks support mute/solo states
• Playback always starts from cursor position, can resume

• Sequence steps are values of ONE Scene's channels (bound to track). Chaser steps can be ANY function.
• Sequences in Show Manager always play Forward. Chasers support all run orders.
• Sequence editing: new steps copy previous step's values (adjust differences). Chaser editing: pick existing functions.
• Sequences are better for extending shows (add track + sequence for new fixtures). Chasers require complex Collections for sync.

Script

Workspace XML (.qxw) Structure

<Function>

ID

Type

Name

Path

Hidden

BlendMode

<Workspace>
  <Creator>...</Creator>
  <Engine>
    <InputOutputMap>...</InputOutputMap>
    <Fixture>...</Fixture>
    <FixtureGroup>...</FixtureGroup>
    <ChannelsGroup>...</ChannelsGroup>
    <Function ID="N" Type="Scene" Name="...">
      <Tempo Type="Time"/>
      <Speed FadeIn="0" FadeOut="0" Duration="0"/>
      <ChannelGroupsValues>id,level,id,level</ChannelGroupsValues>
      <FixtureVal ID="fixture_id">ch_num,value,ch_num,value,...</FixtureVal>
      <FixtureGroup ID="0"/>
      <Palette ID="0"/>
    </Function>
    <Function ID="N" Type="Chaser" Name="...">
      <Tempo Type="Time"/>
      <Speed FadeIn="0" FadeOut="0" Duration="0"/>
      <Direction>Forward</Direction>
      <RunOrder>SingleShot</RunOrder>
      <SpeedModes FadeIn="Default" FadeOut="Default" Duration="PerStep"/>
      <Step Number="0" FadeIn="0" Hold="8000" FadeOut="0" Note="">scene_id</Step>
    </Function>
    <Function ID="N" Type="Collection" Name="...">
      <Step Number="0">function_id</Step>
      <Step Number="1">function_id</Step>
    </Function>
    <Function ID="N" Type="EFX" Name="...">
      <PropagationMode>Parallel</PropagationMode>
      <Algorithm>Circle</Algorithm>
      <Width>127</Width>
      <Height>127</Height>
      <Rotation>0</Rotation>
      <Speed FadeIn="0" FadeOut="0" Duration="20000"/>
      <Direction>Forward</Direction>
      <RunOrder>Loop</RunOrder>
      <Fixture>...</Fixture>
    </Function>
  </Engine>
  <VirtualConsole>...</VirtualConsole>
</Workspace>

Scene FixtureVal format

<FixtureVal ID="fixture_id">channel,value,channel,value,...</FixtureVal>

• Channel numbers are 0-indexed relative to the fixture
• Values are 0-255
• Empty FixtureVal (

  <FixtureVal ID="3"/>

  ) means fixture participates but no values set

Chaser Step format

<Step Number="N" FadeIn="ms" Hold="ms" FadeOut="ms" Note="">function_id</Step>

• Times in milliseconds
• function_id references the Function ID of the step content
• Tempo Type="Beats": values are multiples of 1000 (1000 = 1 beat)

Virtual Console

Button

Slider

Cue List

• Can ONLY be assigned a Chaser
• Steps through with Next/Previous/Play/Stop
• Crossfade fader for manual transitions
• Set step duration to infinite (∞) for manual crossfade control
• Duration=0 causes frantic looping — always set explicit durations

Solo Frame

Frame

Fixture Definitions

• Manufacturer, Model, Type
• Physical properties (bulb, beam angle, dimensions)
• Channels with groups (Intensity, Pan, Tilt, Gobo, Color, Speed)
• Capabilities per channel (value ranges → names/functions)
• Modes (different channel configurations for the same fixture)

Fixture Modes

Heads

Input/Output & Plugins

• Art-Net (network DMX)
• E1.31/sACN (network DMX)
• DMX USB (Enttec, FTDI adapters)
• MIDI (input/output for controllers)
• OSC (Open Sound Control)
• HID (joysticks, gamepads)
• Loopback (internal routing)

Common Pitfalls

1. Hold="0" on sub-chaser steps — causes them to be skipped entirely
2. SpeedModes FadeIn="PerStep" on main song chaser — causes timing drift vs "Default"
3. Fade Out expects LTP channels to fade — they don't; only HTP channels fade
4. Two scenes setting same LTP channel — last-started wins, can cause unexpected jumps
5. Cue List with duration=0 steps — frantic looping with no visible result
6. Forgetting channel enable/disable — a scene with a channel disabled will never touch that channel, even if it looks like it should
7. HTP conflicts when layering monolithic scenes — if both scenes set intensity, highest wins, not the "current" one

Timing Calculations

• sum(all step Hold values) == song duration

  (for SingleShot chasers)
• Sub-chaser Hold = sum of sub-chaser's own steps' total durations
• FadeIn happens WITHIN the Hold window (with Default SpeedMode), not in addition to it

Best Practices

• Use

  SpeedModes FadeIn="Default" FadeOut="Default" Duration="PerStep"

  for song chasers
• Give sub-chaser steps explicit Hold values matching their total runtime
• Never hold a single static scene longer than ~12s in performance
• Create front/rear intensity contrast for depth (not symmetric values)
• Use Solo Frames to prevent accidental scene stacking
• Keep strobe for punctuation, not atmosphere