ScopeDoom

DOOM rendered on a hardware oscilloscope via sound card

Overview

ScopeDoom renders DOOM's 3D world as wireframe vector graphics on a real oscilloscope. It uses your computer's sound card as a dual-channel DAC - the left channel drives the X-axis, the right channel drives the Y-axis, and the scope displays in X-Y mode.

How It Works

DOOM Engine (C)
    |
    | Extract walls & entities as vectors
    v
Unix Domain Socket
    |
    | JSON: {walls: [...], entities: [...]}
    v
doom_scope.py (Python)
    |
    | Convert to X-Y point stream
    v
Sound Card (44.1kHz stereo)
    |
    | Left = X, Right = Y
    v
Oscilloscope (X-Y Mode)

Key Components

• doom_scope.py - Main renderer that receives DOOM vectors and outputs audio
• scope_capture.py - Capture oscilloscope screenshots via VXI-11 (Siglent scopes)
• scope_output.py - Test patterns (squares, circles) for scope calibration
• doom/source/ - Modified DOOM engine with vector extraction

Hardware Setup

What You Need

• Computer with 3.5mm audio output (or USB audio interface)
• Oscilloscope with X-Y mode
• Two load resistors (1k ohm recommended)
• Audio cable (3.5mm to bare wires or RCA)

Wiring

MacBook Pro 3.5mm Jack
        |
        +--- Left (Tip) ----[1k]----+---- CH1 (X)
        |                           |
        +--- Right (Ring) --[1k]----+---- CH2 (Y)
        |                           |
        +--- Ground (Sleeve) -------+---- GND

Scope Settings

• Mode: X-Y
• Channel 1: X input (left audio)
• Channel 2: Y input (right audio)
• Scale: Start at 500mV/div, adjust as needed
• Coupling: DC or AC (AC removes DC offset from audio)

Quick Start

1. Test Your Setup

# Generate test patterns (no DOOM needed)
python3 scope_wav_test.py
afplay scope_square.wav  # Should show a square on scope

2. Run with DOOM

# Terminal 1: Start the scope renderer
python3 doom_scope.py

# Terminal 2: Launch DOOM (from doomgeneric build)
./doomgeneric_kicad -w 1 1

3. Play!

• Controls work in the SDL window
• Scope displays wireframe view in real-time
• WASD to move, arrows to turn, Ctrl to fire

Building DOOM

ScopeDoom requires a modified DOOM engine that extracts vector data. See doom/source/build.sh for build instructions.

The key modification is extracting wall segments (drawsegs[]) and sprite positions (vissprites[]) and sending them over a Unix socket as JSON.

Performance

Metric	Value
Sample Rate	44,100 Hz
Points per Frame	~5,000-10,000
Effective Refresh	4-8 Hz
Walls Rendered	30-50 typical
Entities Rendered	0-10

The refresh rate depends on scene complexity. More walls/entities = more points = slower refresh. But it's still playable!

Dependencies

pip install sounddevice numpy

Optional (for scope screenshots):

pip install python-vxi11

Files

ScopeDoom/
├── doom_scope.py      # Main DOOM-to-scope renderer
├── scope_capture.py   # Oscilloscope screenshot capture
├── scope_output.py    # Test pattern generator
├── scope_wav_test.py  # WAV file test patterns
├── assets/            # Screenshots and demos
└── doom/source/       # Modified DOOM engine source

Known Issues

• DC Offset - Mac audio has DC bias, image may not be centered
• Visible Retrace - No Z-axis blanking, beam movement visible
• Aliasing - Limited sample rate causes stepping on diagonals

Future Ideas

• Z-axis blanking with 3-channel audio interface
• Higher sample rate (96kHz/192kHz audio)
• Optimize point ordering to minimize retrace
• Add simple HUD elements

Credits

• DOOM by id Software
• doomgeneric portable DOOM
• Inspired by oscilloscope music artists and Vectrex DOOM

License

GPL (inherits from DOOM source code)