コンテンツにスキップ

Fixing collision issues with clone sprites lagging behind camera movement

このコンテンツはまだ日本語訳がありません。

💡 Having trouble with Scratch block assembly? Don’t know how to implement code logic? 🚀 Get Help Now

GJ

GameDev_Jordan

Posted on July 24, 2025 • Advanced

🎮 Camera lag causing collision problems

Hey everyone! I’m working on a top-down scrolling game and running into a frustrating issue:

  • Clone sprites (like loot crates) lag behind camera movement
  • This causes collision detection problems
  • Player gets stuck in objects due to positioning mismatch
  • Movement looks jittery and unprofessional

I tried using stamps but that created layering and collision issues. Is there a proper way to synchronize camera movement with clone positioning? 🤔

CE

CameraExpert_Pro

Replied 4 hours later • ⭐ Best Answer

Excellent question @GameDev_Jordan! This is a classic execution order problem in scrolling games. Let me show you the proper solution:

🔄 The Problem: Execution Order

Here’s what’s happening in your current setup:

flowchart TD A[🎬 Frame Start] --> B[Update Loot Position] B --> C[Update Player Position] C --> D[Update Camera Scroll] D --> E[Update Background] E --> F[🎬 Frame End] F --> G[🎬 Next Frame Start] G --> H[Loot Uses OLD Scroll Values] H --> I[Player Uses NEW Scroll Values] I --> J[❌ Desync!] style A fill:#e1f5fe style J fill:#ffebee style H fill:#fff3e0 style I fill:#e8f5e8

✅ The Solution: Controlled Execution Order

We need to control the order using broadcasts:

flowchart TD A[🎬 Main Game Loop] --> B[Broadcast: Update Player] B --> C[Player Updates Position] C --> D[Player Updates Camera Scroll] D --> E[Broadcast: Update World] E --> F[All Objects Update Together] F --> G[Broadcast: Update UI] G --> H[UI Elements Update] H --> I[✅ Perfect Sync!] style A fill:#e1f5fe style I fill:#e8f5e8 style F fill:#f3e5f5

🎮 Main Game Loop (Stage or Controller Sprite)

Create a central controller that manages execution order:

    when flag clicked
forever
// Step 1: Update player and camera
broadcast [update player v] and wait

// Step 2: Update all world objects
broadcast [update world v] and wait

// Step 3: Update UI elements
broadcast [update ui v] and wait

// Optional: Add frame rate control
wait (0.016) seconds // ~60 FPS
end

🏃 Player Sprite Code

Player handles movement and camera updates:

    when I receive [update player v]
// Handle player input
if <key [up arrow v] pressed?> then
change y by (5)
end
if <key [down arrow v] pressed?> then
change y by (-5)
end
if <key [left arrow v] pressed?> then
change x by (-5)
end
if <key [right arrow v] pressed?> then
change x by (5)
end

// Update camera scroll values
set [camera x v] to (x position)
set [camera y v] to (y position)

// Keep player centered on screen
go to x: (0) y: (0)

📦 Loot Crate/Object Sprites

Objects update their positions based on camera:

    when I receive [update world v]
// Calculate screen position based on world position and camera
set [screen x v] to ((world x) - (camera x))
set [screen y v] to ((world y) - (camera y))

// Move to calculated position
go to x: (screen x) y: (screen y)

// Check if object should be visible
if <<(screen x) > [-300]> and <<(screen x) < [300]> and <<(screen y) > [-200]> and <(screen y) < [200]>>>> then
show
else
hide
end

🔧 Clone Management System

For clones, use this pattern:

    // Main sprite creates clones with world positions
when flag clicked
set [world x v] to [100]
set [world y v] to [50]
create clone of [myself v]

set [world x v] to [200]
set [world y v] to [100]
create clone of [myself v]

// Hide main sprite
hide

// Clone behavior
when I start as a clone
set [my world x v] to (world x)
set [my world y v] to (world y)
show

when I receive [update world v]
// Each clone updates its screen position
set [screen x v] to ((my world x) - (camera x))
set [screen y v] to ((my world y) - (camera y))
go to x: (screen x) y: (screen y)

// Collision detection with player
if <touching [Player v]?> then
// Handle collision
broadcast [item collected v]
delete this clone
end

🚀 Advanced Optimization

For better performance with many objects:

    // Only update visible objects
when I receive [update world v]
set [screen x v] to ((my world x) - (camera x))
set [screen y v] to ((my world y) - (camera y))

// Culling: only process if on screen
if <<(screen x) > [-350]> and <<(screen x) < [350]> and <<(screen y) > [-250]> and <(screen y) < [250]>>>> then
go to x: (screen x) y: (screen y)
show

// Only check collisions for visible objects
if <touching [Player v]?> then
// Handle collision
end
else
hide
end

💡 Pro Tips

  • Use “and wait”: Ensures each step completes before the next
  • Separate world and screen coordinates: Makes positioning logic clearer
  • Implement object culling: Hide off-screen objects for better performance
  • Test with many objects: Make sure performance stays smooth

This approach eliminates lag and creates smooth, professional-looking camera movement! 🎯

GJ

GameDev_Jordan

Replied 2 hours later

@CameraExpert_Pro This is exactly what I needed! 🙌

The broadcast system with “and wait” completely solved the synchronization issue. My loot crates now move perfectly smooth with the camera, and collision detection works flawlessly.

The object culling tip is brilliant too - my game runs much smoother now with lots of objects on screen. Thank you!

PO

PerformanceOptimizer

Replied 1 hour later

Great solution! Here are some additional performance tips for large scrolling worlds:

⚡ Performance Enhancements

  • Chunk loading: Only create clones for objects near the player
  • Distance-based updates: Update distant objects less frequently
  • Pooling system: Reuse clones instead of constantly creating/deleting
    // Distance-based update frequency
when I receive [update world v]
set [distance to player v] to (distance to [Player v])

if <(distance to player) < [100]> then
// Update every frame (smooth)
go to x: ((my world x) - (camera x)) y: ((my world y) - (camera y))
else
if <(distance to player) < [300]> then
// Update every 3rd frame
if <((timer) mod (3)) = [0]> then
go to x: ((my world x) - (camera x)) y: ((my world y) - (camera y))
end
end
end

This keeps your game running smoothly even with hundreds of objects! 🚀

VB

Vibelf_Community

Pinned Message • Moderator

🎮 Master Advanced Game Development

Excellent discussion on camera systems and performance optimization! Ready to create professional-quality games? Our community can help you master:

  • 🎯 Advanced camera systems and smooth following
  • ⚡ Performance optimization for complex games
  • 🔧 Professional game architecture patterns
  • 🎨 Advanced collision detection systems

📚 Related Topics

Ready to build the next great Scratch game? Get personalized guidance from our game development experts in the Vibelf app!