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Help with clone detection in Scratch games

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CM

CodeMaster_Alex

Posted on January 25, 2024 • Intermediate

🎮 Clone detection not working properly

Hey everyone! I’m working on a game where I need clones to detect and interact with other clones, but it’s not working as expected. The clones seem to ignore each other completely.

  • Clones should detect when they touch other clones
  • Need proper collision detection between clone instances
  • Want to trigger events when clones interact

I’ve tried using the basic touching blocks but they don’t seem to work with clones. Any help would be greatly appreciated! 🙏

GD

GameDev_Expert

Replied 3 hours later • ⭐ Best Answer

Great question @CodeMaster_Alex! Clone detection is tricky but totally doable. The key is understanding how clones work in Scratch. Here’s a comprehensive solution:

🔍 Clone Detection Flow

Here’s how proper clone-to-clone detection works:

flowchart TD A[🚀 Clone Created] --> B[Set Unique ID] B --> C[Start Detection Loop] C --> D{Check All Sprites?} D -->|Yes| E[Loop Through Sprites] D -->|No| F[Use Broadcast Method] E --> G{Touching Sprite?} G -->|Yes| H[Check if Clone] G -->|No| E H -->|Is Clone| I[🎯 Collision Detected] H -->|Not Clone| E F --> J[Broadcast Position] J --> K[Receive & Compare] K --> L{Distance < Threshold?} L -->|Yes| I L -->|No| C I --> M[Trigger Event] M --> N[Handle Collision] N --> C style A fill:#e1f5fe style B fill:#f3e5f5 style I fill:#e8f5e8 style M fill:#fff3e0

🔧 Method 1: Using Touching Detection

The most straightforward approach using sprite detection:

    when I start as a clone
set [my id v] to (pick random [1] to [9999])
forever
if <touching [sprite name v]?> then
broadcast [clone collision v]
wait [0.1] seconds
end
end
  

📡 Method 2: Broadcast-Based Detection

More reliable method using broadcasts and position checking:

    when I start as a clone
set [my id v] to (pick random [1] to [9999])
forever
broadcast [check collision v] and wait
wait [0.1] seconds
end

when I receive [check collision v]
if <not <(my id) = (clone id)>> then
if <(distance to [x position v] [y position v]) < [50]> then
broadcast [collision detected v]
end
end
  

📊 Method 3: List-Based Clone Tracking

Advanced method using lists to track all clones:

    // When clone starts
when I start as a clone
set [my id v] to (length of [clone list v])
add (join (join (x position) [,]) (y position)) to [clone list v]
forever
replace item (my id) of [clone list v] with (join (join (x position) [,]) (y position))
set [counter v] to [1]
repeat (length of [clone list v])
if <not <(counter) = (my id)>> then
set [other pos v] to (item (counter) of [clone list v])
set [other x v] to (letter [1] to (([position v] of [,] in (other pos)) - [1]) of (other pos))
set [other y v] to (letter (([position v] of [,] in (other pos)) + [1]) to (length of (other pos)) of (other pos))
if <((([abs v] of ((x position) - (other x))) + ([abs v] of ((y position) - (other y)))) < [50])> then
broadcast [clone collision v]
end
end
change [counter v] by [1]
end
wait [0.1] seconds
end
  

🎯 Collision Response System

How to handle collisions when detected:

    when I receive [clone collision v]
play sound [collision v]
change [score v] by [10]
set [collision effect v] to [3]
repeat [10]
change [collision effect v] by [-0.3]
set [brightness v] effect to (collision effect)
wait [0.05] seconds
end
clear graphic effects
  

🚀 Performance Tips

  • Limit check frequency: Use wait blocks to avoid constant checking
  • Use distance thresholds: Check approximate distance before precise collision
  • Clone cleanup: Remove clones from tracking lists when deleted
  • Optimize for your needs: Choose the method that fits your game’s requirements

The key is that clones are separate instances, so you need to actively check for collisions rather than relying on automatic detection. Hope this helps! 😊

CM

CodeMaster_Alex

Replied 45 minutes later

@GameDev_Expert This is incredibly helpful! Thank you so much! 🎉

I implemented Method 2 and it works perfectly. The broadcast-based detection is exactly what I needed. One follow-up question - how can I make different types of clones react differently to collisions?

CT

CloneTech_Sarah

Replied 1 hour later

@CodeMaster_Alex Great question! For different clone types, use a “clone type” variable:

    when I start as a clone
if <(clone type) = [enemy]> then
set [collision damage v] to [20]
else
if <(clone type) = [powerup]> then
set [collision effect v] to [heal]
end
end

when I receive [collision detected v]
if <(other clone type) = [player]> then
if <(clone type) = [enemy]> then
broadcast [damage player v]
else
if <(clone type) = [powerup]> then
broadcast [heal player v]
end
end
end
  

This way each clone type can have unique collision behaviors! ✨

VB

Vibelf_Community

Pinned Message • Moderator

🚀 Master Advanced Clone Mechanics

Excellent discussion on clone detection! For those looking to implement even more sophisticated clone systems, our community can help you with:

  • 🎯 Multi-layer collision detection
  • 🔄 Clone pooling for performance
  • 🎮 Complex clone AI behaviors
  • ⚡ Optimized clone management systems

📚 Related Topics

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