LuaJIT Win32 & SDL2 Graphics Demos

This project demonstrates parallel implementations of 2D canvas drawing and 3D raytracing using both Win32 API (Windows-only) and SDL2 (cross-platform).

Project Structure

Canvas Demos (2D Drawing)

• canvas-winapi.lua - Win32 GDI canvas with red rectangle
• canvas-sdl2.lua - SDL2 canvas with red rectangle (cross-platform)

Raytracing Demos (3D Rendering)

• ray3d-winapi.lua - Win32 raytracer with reflections, shadows, animated spheres
• ray3d-sdl2.lua - SDL2 raytracer with same features (cross-platform)

Features Comparison

Canvas Demos

Feature	Win32	SDL2
2D rectangle drawing	✓	✓
Mouse cursor visible	✓	✓
Escape key exits	✓	✓
Window resize	✓	✓
Platform	Windows only	Cross-platform

Raytracing Demos

Feature	Win32	SDL2
3 animated spheres (RGB)	✓	✓
Reflective surfaces	✓	✓
Checkerboard floor	✓	✓
Dynamic shadows	✓	✓
Multi-bounce reflections	✓	✓
Dynamic resolution	✓	✓
Smooth time-based animation	✓	✓
Escape key exits	✓	✓
Platform	Windows only	Cross-platform

Running the Demos

Win32 Versions (Windows with Wine)

cd /home/arkenidar/luajit/win_script
wine luajit.exe canvas-winapi.lua
wine luajit.exe ray3d-winapi.lua

SDL2 Versions (Native Linux)

cd /home/arkenidar/luajit/win_script
luajit canvas-sdl2.lua
luajit ray3d-sdl2.lua

Requirements

For Win32 versions:

• Wine (Linux) or Windows
• LuaJIT (Windows build: luajit.exe)

For SDL2 versions:

• LuaJIT (native build)
• SDL2 library (libSDL2-2.0.so.0 on Linux, SDL2.dll on Windows)

Install SDL2 on Linux:

sudo apt-get install libsdl2-2.0-0

Technical Details

Win32 Implementation

• Uses FFI to call Win32 APIs: user32.dll, kernel32.dll, gdi32.dll
• GDI for 2D drawing (Rectangle, CreateSolidBrush)
• StretchDIBits for pixel buffer rendering (raytracer)
• Win32 message loop (GetMessageW, DispatchMessageW)
• Timer-based animation (SetTimer, WM_TIMER)

SDL2 Implementation

• Uses FFI to call SDL2 APIs
• SDL2 renderer for 2D drawing
• SDL_Texture with streaming for pixel buffer rendering (raytracer)
• SDL2 event loop (SDL_PollEvent)
• Time-based animation (SDL_GetTicks)
• Automatic library detection (Linux .so / Windows .dll)

Raytracer Features

• Camera model: Perspective projection with aspect ratio correction
• Ray-sphere intersection: Analytic quadratic solution
• Ray-plane intersection: Floor at y = -2
• Lighting: Single directional light with diffuse shading
• Shadows: Ray tracing from hit point to light source
• Reflections: Recursive ray tracing (max depth 2)
• Materials: Configurable reflectivity per sphere (0.6-0.7)
• Animation: Spheres orbit around center using time-based rotation
• Dynamic resolution: Renders at exact window size (no oversampling)

Code Structure

Both Win32 and SDL2 versions follow the same logical structure:

1. FFI Declarations: Platform-specific API types and functions
2. Utility Functions: wstr() for Win32, helper functions
3. Raytracer Logic:
   • raytrace(w, h, angle) - Main rendering loop
   • trace_ray() - Recursive ray tracer
   • is_in_shadow() - Shadow testing
4. Window/Event Handling: Platform-specific message/event loop
5. Main Function: Window creation and initialization

Performance

• Win32: ~30-60 FPS at 640x480 (depends on CPU)
• SDL2: Similar performance to Win32
• Rendering: Real-time ray tracing with reflections and shadows
• Resolution: Dynamically adjusts to window size

Future Enhancements

Possible improvements:

• Anti-aliasing (supersampling)
• More complex geometry (triangles, meshes)
• Multiple light sources
• Texture mapping
• Refractions (transparent materials)
• Depth of field
• Ambient occlusion
• Path tracing

License

Educational/demonstration code. Use freely.