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How to make sprites follow a path in tower defense games

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PM

PathMaster_Dev

Posted on January 22, 2024 • Intermediate

🎮 Tower Defense Path Following Problem

Hey everyone! I’m working on a tower defense game in Scratch and I’m having trouble making enemies follow the designated path. Currently, my enemies just move toward the center of the path sprite instead of following the actual route. Here’s what I’m trying to achieve:

  • Enemies spawn and follow a predefined path
  • They navigate through turns and curves smoothly
  • Multiple enemies can follow the same path without colliding

My current code just makes them point toward the path sprite and move forward, but they don’t follow the actual path layout. Any help would be greatly appreciated! 🙏

TD

TowerDefense_Expert

Replied 3 hours later • ⭐ Best Answer

Great question @PathMaster_Dev! Path following in tower defense games is a classic challenge. Here are several effective approaches to solve this problem:

🗺️ Path Following System Overview

Here’s how a robust path-following system works:

flowchart TD A[🚀 Enemy Spawns] --> B[Load Waypoint List] B --> C[Set Current Target = First Waypoint] C --> D[🎮 Movement Loop] D --> E{Reached Current Waypoint?} E -->|No| F[Move Toward Current Waypoint] E -->|Yes| G[Next Waypoint Available?] F --> H[Calculate Direction] H --> I[Move Forward] I --> D G -->|Yes| J[Set Next Waypoint as Target] G -->|No| K[🏁 Reached End - Remove Enemy] J --> D style A fill:#e1f5fe style B fill:#f3e5f5 style K fill:#fce4ec style F fill:#e8f5e8

🔧 Method 1: Waypoint System (Recommended)

Create a list of coordinates that define your path:

    when flag clicked
// Create waypoint lists
delete all of [Path X v]
delete all of [Path Y v]

// Add waypoints for your path
add [100] to [Path X v]
add [150] to [Path Y v]
add [200] to [150] to [Path X v]
add [150] to [Path Y v]
add [200] to [Path X v]
add [50] to [Path Y v]
add [300] to [Path X v]
add [50] to [Path Y v]

// Initialize enemy
set [Current Waypoint v] to [1]
set [Speed v] to [3]
  
    // Enemy movement script
when I receive [spawn enemy v]
forever
if <(Current Waypoint) <= (length of [Path X v])> then
// Get target position
set [Target X v] to (item (Current Waypoint) of [Path X v])
set [Target Y v] to (item (Current Waypoint) of [Path Y v])

// Calculate distance to target
set [Distance v] to (sqrt of (((Target X) - (x position)) * ((Target X) - (x position))) + (((Target Y) - (y position)) * ((Target Y) - (y position))))

if <(Distance) < [10]> then
// Reached waypoint, move to next
change [Current Waypoint v] by [1]
else
// Move toward current waypoint
point towards x: (Target X) y: (Target Y)
move (Speed) steps
end
else
// Reached end of path
broadcast [enemy reached end v]
delete this clone
end
end

🎨 Method 2: Color-Based Path Following

Use different colors on your path sprite to control movement direction:

    when flag clicked
forever
// Check color beneath enemy
if <touching color [#ff0000]?> then
point in direction [90] // Right
end
if <touching color [#00ff00]?> then
point in direction [0] // Up
end
if <touching color [#0000ff]?> then
point in direction [-90] // Left
end
if <touching color [#ffff00]?> then
point in direction [180] // Down
end

move (3) steps

// If off path, find nearest path color
if <not <touching color [#ff0000]?>> and <not <touching color [#00ff00]?>> and <not <touching color [#0000ff]?>> and <not <touching color [#ffff00]?>> then
// Return to path logic here
end
end

🚀 Method 3: Advanced Smooth Following

For smoother movement with curves:

    // Smooth path following with interpolation
define move to waypoint (target x) (target y)
set [dx v] to ((target x) - (x position))
set [dy v] to ((target y) - (y position))
set [distance v] to (sqrt of ((dx) * (dx)) + ((dy) * (dy)))

if <(distance) > [5]> then
// Normalize direction and apply speed
set [move x v] to (((dx) / (distance)) * (Speed))
set [move y v] to (((dy) / (distance)) * (Speed))

change x by (move x)
change y by (move y)

// Smooth rotation
set [target direction v] to ((atan of ((dy) / (dx))) + (90))
if <(dx) < [0]> then
change [target direction v] by [180]
end

// Gradually turn toward target direction
set [angle diff v] to ((target direction) - (direction))
if <(angle diff) > [180]> then
change [angle diff v] by [-360]
end
if <(angle diff) < [-180]> then
change [angle diff v] by [360]
end

turn right ((angle diff) / [5]) degrees
end

💡 Pro Tips for Better Path Following

  • Waypoint Spacing: Place waypoints closer together for smoother curves
  • Speed Control: Slow down near waypoints to prevent overshooting
  • Multiple Paths: Use different lists for different difficulty levels
  • Enemy Spacing: Add delays between spawns to prevent clustering
    // Enemy spawning with proper spacing
when flag clicked
repeat [10]
broadcast [spawn enemy v]
wait [1.5] seconds // Spacing between enemies
end

The waypoint method is most reliable and gives you complete control over the path. Start with that approach and you’ll have enemies following your path perfectly! 😊

PM

PathMaster_Dev

Replied 45 minutes later

@TowerDefense_Expert This is absolutely perfect! 🎉

The waypoint system worked like a charm! My enemies are now following the path exactly as intended. The smooth interpolation method is especially nice for making the movement look more natural.

Quick question - how would I handle multiple enemy types with different speeds on the same path?

GD

GameDev_Sarah

Replied 2 hours later

@PathMaster_Dev For different enemy types, just use a variable for each enemy’s speed! Here’s how:

    // When creating enemy clone
when I start as a clone
if <(Enemy Type) = [fast]> then
set [Speed v] to [5]
else
if <(Enemy Type) = [slow]> then
set [Speed v] to [2]
else
set [Speed v] to [3] // normal speed
end
end

This way each enemy maintains its own speed while following the same path! 🚀

VB

Vibelf_Community

Pinned Message • Moderator

🚀 Ready to Build Advanced Tower Defense Games?

Excellent discussion on path following mechanics! For those looking to create even more sophisticated tower defense systems, our community can help you implement:

  • 🎯 Advanced AI pathfinding algorithms
  • 🏰 Dynamic tower placement systems
  • ⚡ Special abilities and power-ups
  • 🌊 Wave management and difficulty scaling

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