Lumen

A C++ simulation and rendering engine exploring light, physics, and real-time systems.

Overview

Lumen is a ground-up C++ project focused on understanding how light, motion, and simulation work at their most fundamental level.

The project currently implements a real-time 2D ray casting system using SDL2, featuring a movable light source, dynamic shadow casting, and animated obstacles. Lumen is designed as a long-term learning and experimentation platform that will gradually evolve into a full simulation engine.

Rather than relying on high-level frameworks, Lumen emphasizes low-level control, clear math, and deterministic systems.

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Current Features

• Mouse-controlled light source
  • Rays originate from a point light that follows mouse movement
• Real-time shadow casting
  • Rays terminate on obstacle collision or screen bounds
• Animated obstacles
  • Circular objects move dynamically over time
• Ray marching
  • Rays advance step-by-step using trigonometry
• Software rendering
  • Pixel-level rendering using SDL surfaces

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How It Works

• Rays are generated uniformly in 360° around the light source
• Each ray:
  • Steps forward using cos(angle) and sin(angle)
  • Draws pixels incrementally
  • Stops when it:
    • Intersects an obstacle (circle collision)
    • Exits the screen
• Shadows emerge naturally as blocked rays stop propagating

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Tech Stack

• Language: C++
• Library: SDL2
• Rendering: Software (pixel-by-pixel)
• Math: Trigonometry, distance checks, ray marching

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Inspiration

Lumen is inspired by creators and educators who focus on building systems from first principles:

• Daniel Hirsch — ray casting & graphics fundamentals
• AngeTheGreat — simulation-driven engine design
• Pezzza — creative coding & visual experimentation

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Roadmap

Lumen is intended to grow into a broader simulation engine. Planned explorations include:

• Gravity & rigid body dynamics
• Fluid simulation
• Smoke & particle systems
• Cloth simulation
• Engine architecture inspired by AngeTheGreat & Pezzza
• Transition from simple ray casting to complex simulations

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Build & Run

Requirements

• SDL2
• MinGW / g++

Compile

g++ ray_tracing.cpp -o lumen \
  -I C:/MinGW/include \
  -L C:/MinGW/lib \
  -lmingw32 -lSDL2main -lSDL2 -lm