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💥 Collision Detection

Master AABB, circle collision, SAT, and advanced collision detection algorithms

⏱️ 4 hours📚 9 sections⚡ Intermediate

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Sections

💥

Introduction to Collision Detection

Section 1 of 9

Collision detection is essential for making games feel interactive and realistic. It determines when objects in your game touch, overlap, or collide with each other. **Why Collision Detection Matters:** • Core gameplay mechanic (hitting enemies, collecting items, blocking obstacles) • Physics interactions (bouncing, stopping, sliding) • Game boundaries (keeping player inside the level) • Trigger zones (starting events, changing areas) **Common Use Cases:** • Player vs Enemies/Obstacles • Projectiles vs Targets • Player vs Collectibles • Platforms vs Character feet • Trigger zones for events **Performance Considerations:** Checking every object against every other object is expensive! For 100 objects, that's 4,950 checks per frame. We need efficient algorithms. **Types We'll Cover:** 1. AABB (Axis-Aligned Bounding Box) - Fast, simple rectangles 2. Circle Collision - Perfect for round objects 3. Point vs Shape - Mouse clicks, projectiles 4. SAT (Separating Axis Theorem) - Rotated rectangles 5. Pixel-Perfect - Most accurate, slowest

💻Code Example

// Basic collision detection structure
class GameObject {
  constructor(x, y, width, height) {
    this.x = x;
    this.y = y;
    this.width = width;
    this.height = height;
  }
  
  // Check if this object collides with another
  collidesWith(other) {
    // We'll implement different methods here
    return false;
  }
}

// Game loop with collision checking
const player = new GameObject(100, 100, 50, 50);
const enemies = [
  new GameObject(200, 150, 40, 40),
  new GameObject(300, 200, 40, 40)
];

function update() {
  // Check collisions
  enemies.forEach(enemy => {
    if (player.collidesWith(enemy)) {
      console.log('Hit enemy!');
      handleCollision(player, enemy);
    }
  });
}

function handleCollision(obj1, obj2) {
  // Response: damage, bounce, collect, etc.
  console.log('Collision detected!');
}

🎯 Key Takeaways

  • •AABB is fastest for axis-aligned rectangles, perfect for platformers
  • •Circle collision is ideal for round objects and very efficient
  • •SAT handles rotated shapes and any convex polygon
  • •Spatial partitioning dramatically improves performance for many objects
  • •Proper collision response makes games feel polished and realistic

🚀 Practice Challenge

Build a physics-based game demonstrating collision mastery:

  • 1.Create bouncing balls with circle collision detection
  • 2.Add platforms using AABB for walls and floors
  • 3.Implement spatial grid for optimized collision checks
  • 4.Add realistic bounce physics with restitution
  • 5.Create collectible items with point collision detection
Try the Challenge →

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