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Fixing sprite position glitches at specific coordinates

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CG

CloudGameDev

Posted on January 22, 2024 • Intermediate

🐛 Sprite glitches at specific coordinates

I’m working on a cloud-based multiplayer game in Scratch, but I’m encountering strange glitches when my sprite reaches specific coordinates like x=-99, x=99, y=-99, or y=99. The sprite behavior becomes unpredictable at these positions.

Here’s what happens:

  • Sprite movement becomes erratic at coordinate boundaries
  • Position detection fails at exactly -99 or 99
  • Cloud variable synchronization breaks down
  • Other sprites can’t properly detect the glitched sprite

I suspect it’s related to my conditional statements, but I can’t figure out what’s wrong. Any debugging help would be greatly appreciated! 🙏

DB

DebugMaster_Alex

Replied 1 hour later • ⭐ Best Answer

Great question @CloudGameDev! This is a classic conditional logic bug that many developers encounter. The issue is with how you’re handling boundary conditions in your if-else statements.

🔍 Problem Analysis

The glitch occurs because your conditional statements don’t properly handle the exact boundary values (-99 and 99). Here’s what’s happening:

flowchart TD A[🎯 Position Check] --> B{x > 99?} B -->|Yes| C[Handle x > 99] B -->|No| D{x < 99?} D -->|Yes| E[Handle x < 99] D -->|No| F[❌ x = 99 UNHANDLED!] G[🎯 Position Check] --> H{x > -99?} H -->|Yes| I[Handle x > -99] H -->|No| J{x < -99?} J -->|Yes| K[Handle x < -99] J -->|No| L[❌ x = -99 UNHANDLED!] style F fill:#ffebee style L fill:#ffebee style C fill:#e8f5e8 style E fill:#e8f5e8 style I fill:#e8f5e8 style K fill:#e8f5e8

🐛 Common Problematic Code Pattern

Here’s the typical buggy pattern that causes this issue:

    define handle position
if <(x position) > [99]> then
set [xy v] to (join (xy) (x position))
else
if <(x position) < [99]> then
// Handle normal position
set [xy v] to (join (xy) (x position))
end
end

✅ Corrected Code Solution

Here’s the fixed version that properly handles all boundary conditions:

    define handle position
if <(x position) > [99]> then
// Handle positions greater than 99
set [xy v] to (join (xy) [99])
set x to [99]
else
if <(x position) < [-99]> then
// Handle positions less than -99
set [xy v] to (join (xy) [-99])
set x to [-99]
else
// Handle all positions between -99 and 99 (inclusive)
set [xy v] to (join (xy) (x position))
end
end

🔧 Better Approach: Range Clamping

For even cleaner code, use a clamping function:

    define clamp (value) between (min) and (max)
if <(value) < (min)> then
set [clamped value v] to (min)
else
if <(value) > (max)> then
set [clamped value v] to (max)
else
set [clamped value v] to (value)
end
end

// Usage in your main code
clamp (x position) between [-99] and [99]
set x to (clamped value)
set [xy v] to (join (xy) (clamped value))

🚀 Advanced: Cloud Game Optimization

For cloud games, add position validation before sending data:

    define send position to cloud
// Validate and clamp positions
clamp (x position) between [-99] and [99]
set [validated x v] to (clamped value)
clamp (y position) between [-99] and [99]
set [validated y v] to (clamped value)

// Only send if position actually changed
if <not <((validated x) = (last sent x)) and ((validated y) = (last sent y))>> then
set [☁ player x v] to (validated x)
set [☁ player y v] to (validated y)
set [last sent x v] to (validated x)
set [last sent y v] to (validated y)
end

This approach ensures your cloud game stays synchronized and prevents the boundary glitches! 🎮

CG

CloudGameDev

Replied 45 minutes later

@DebugMaster_Alex This is absolutely perfect! 🎉 The clamping function approach is exactly what I needed!

I implemented your solution and the glitches are completely gone. My cloud game is now running smoothly at all coordinate boundaries. Thank you so much for the detailed explanation and the optimization tips!

CT

CloudTech_Sarah

Replied 2 hours later

Great solution! For anyone working with cloud games, here are some additional tips to prevent similar issues:

  • Input validation: Always validate data before processing
  • Boundary testing: Test edge cases like -99, -100, 99, 100
  • Error handling: Add fallback behaviors for unexpected values
  • Performance: Only update cloud variables when values actually change

These practices will make your cloud games much more robust! 🛡️

VB

Vibelf_Community

Pinned Message • Moderator

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Excellent debugging discussion! For developers looking to master more advanced debugging and optimization techniques, our community can help you with:

  • 🔍 Advanced conditional logic debugging
  • ⚡ Cloud game performance optimization
  • 🛡️ Robust error handling patterns
  • 🧪 Comprehensive testing strategies

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