Sand Falling Simulator (C++ & SDL2)

Interactive falling-sand sandbox built in C++ using SDL2.
Click to drop sand and watch it fall, stack, and slide with simple physics.
Includes a Restart button, Exit button, pixel-art grid and smooth simulation loop.

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Features

• Falling sand physics using a cellular-automata model
• Pixel grid visual style
• Click to spawn sand
• Restart button to clear the screen
• Exit button to stop the app
• UI for materials
• SDL2 rendering with VSync
• Easy to extend (new materials like water, stone, etc.)

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Requirements (macOS)

You need these installed:

• Homebrew
• Xcode Command Line Tools
• SDL2
• SDL2_ttf (for rendering text )

Install if needed:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)" xcode-select --install brew install sdl2 sdl2_ttf

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Add Font File

Place a .ttf font in the same folder as sand.cpp, for example:

OpenSans-Regular.ttf

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Build & Run (macOS)

Compile using:

clang++ sand.cpp -o sand
-I/opt/homebrew/include
-I/opt/homebrew/opt/sdl2/include
-I/opt/homebrew/opt/sdl2_ttf/include
-L/opt/homebrew/lib
-L/opt/homebrew/opt/sdl2/lib
-L/opt/homebrew/opt/sdl2_ttf/lib
-lSDL2 -lSDL2_ttf

Then run:

./sand

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Controls

Hold Left Mouse Button → Spawn falling sand
Click Restart Button → Clear the world Click Exit Button → Exit the world Close Window → Exit the app

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How It Works

Each sand grain acts as a cell in a fixed grid.

Every frame, each grain tries in order:

1. Move down
2. Move down-left or down-right if blocked
3. Otherwise stay put

This produces realistic piling and sliding behavior.

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Planned Improvements

• Water, stone, smoke materials
• Right-click → eraser
• Brush size options
• Randomized sand color variation
• Save/load sandbox state

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License

MIT License

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Author

Pranav Kumar