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Overview

In QLC+, a Universe represents a DMX universe - a collection of 512 DMX channels used to control lighting fixtures and effects. The Universe class is the fundamental container for managing input/output data and translating control values into DMX signals.
QLC+ supports multiple universes, allowing you to control more than 512 channels by organizing fixtures across different DMX universes.

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Universe Basics

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Size and Structure

Each universe in QLC+ contains exactly 512 channels (defined as UNIVERSE_SIZE), following the DMX512 standard. Each channel can hold a value from 0 to 255. 
#define UNIVERSE_SIZE 512

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Universe Properties

  • ID: Zero-based universe identifier (e.g., Universe 0, Universe 1)
  • Name: Friendly name for easy identification
  • Passthrough Mode: Allows input signals to pass directly to output
  • Monitor Mode: Enables monitoring of universe changes

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Channel Types

QLC+ categorizes channels into different types to optimize DMX value processing:

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HTP (Highest Takes Precedence)

Used primarily for intensity channels. When multiple functions control the same channel, the highest value wins. 
enum ChannelType {
    LTP        = 1 << 0,  // Latest Takes Precedence
    HTP        = 1 << 1,  // Highest Takes Precedence  
    Intensity  = 1 << 2   // Intensity channel flag
};

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LTP (Latest Takes Precedence)

Used for position, color, and control channels. The most recent value takes priority, regardless of magnitude.
You can force specific fixture channels to use HTP or LTP behavior, overriding their default channel group behavior.

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Input and Output Patches

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Output Patches

Output patches connect a universe to physical DMX output hardware: 
bool setOutputPatch(QLCIOPlugin *plugin, quint32 output, int index = 0);
  • A universe can have multiple output patches
  • Each patch connects to an I/O plugin (DMX interface, ArtNet, etc.)
  • Output is written at every Master Timer tick

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Input Patches

Input patches receive control signals from external controllers: 
bool setInputPatch(QLCIOPlugin *plugin, quint32 input, 
                   QLCInputProfile *profile = NULL);
  • Associates input hardware with the universe
  • Optional input profile for customizing control behavior
  • Supports passthrough mode for direct input-to-output routing

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Feedback Patches

Feedback patches send control data back to hardware controllers: 
bool setFeedbackPatch(QLCIOPlugin *plugin, quint32 output);
Useful for controllers with LED feedback or motorized faders.

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Value Processing

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Grand Master

The Grand Master is a global intensity control that affects universe output:
  • Limit Mode: Caps intensity at the Grand Master value
  • Reduce Mode: Scales intensity by the Grand Master fraction
  • Can affect intensity channels only or all channels
uchar applyGM(int channel, uchar value) {
    if (grandMaster->channelMode() == GrandMaster::Intensity && 
        m_channelsMask->at(channel) & Intensity) {
        // Apply Grand Master scaling
        value = (value * grandMaster->fraction());
    }
    return value;
}

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Channel Modifiers

Channel modifiers allow custom value transformations before output: 
void setChannelModifier(ushort channel, ChannelModifier *modifier);
Useful for inverting values, creating custom curves, or applying calibration.

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Data Flow

The universe processes DMX data through several stages:
  1. Pre-GM Values: Raw values written by functions
  2. Channel Modifiers: Custom transformations applied
  3. Grand Master: Global intensity scaling
  4. Post-GM Values: Final values ready for output
  5. Output Patches: Physical DMX transmission

Write Operation

Functions write values to channels using write() methods, respecting HTP/LTP rules

Fader System

GenericFader objects compose smooth transitions and priority-based channel control

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Passthrough Mode

Passthrough mode enables input signals to flow directly to output: 
void setPassthrough(bool enable);
  • Input values merge with function output using HTP
  • Useful for manual control during playback
  • Commonly used with MIDI or OSC controllers

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Universe Workflow

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Practical Example

A typical universe setup: 
// Create universe
Universe *universe = new Universe(0, grandMaster, parent);
universe->setName("Main Stage");

// Configure output
universe->setOutputPatch(dmxPlugin, 0, 0);

// Set channel capabilities for a dimmer
universe->setChannelCapability(0, QLCChannel::Intensity, Universe::HTP);

// Write a value (respecting HTP)
universe->write(0, 255, false);

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Best Practices

  • Universe Organization: Group related fixtures in the same universe for easier management
  • Channel Planning: Plan fixture addresses to avoid conflicts and simplify patching
  • HTP vs LTP: Use HTP for intensity, LTP for everything else (position, color, effects)
  • Monitor Efficiency: Only enable monitoring when needed to reduce processing overhead
  • Fixtures - How lighting fixtures are mapped to universe channels
  • Functions - How functions write values to universe channels

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