How to Detect When a Walking NPC is Turning

[mrminiondev]

So, let’s say I have an NPC that is moving around using a humanoid. How would I detect when the NPC is turning/rotating vs moving in a straight line as it moves?

[TheHollowHeart (Neutrality)]

How to Detect When an NPC is Turning or Moving Straight in Roblox Studio

In this tutorial, I’ll explain how you can detect whether an NPC (Non-Player Character) in Roblox is turning or moving in a straight line as it navigates around. I’ll break it down into simple, easy-to-understand steps.

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1. Understanding How NPCs Move

In Roblox, NPCs typically move using a Humanoid or by manually adjusting their position. Each NPC has a HumanoidRootPart, which acts as the main part controlling the NPC’s movement and orientation.

Important Concepts:

• Direction NPC is Facing:
  • The CFrame.LookVector of the HumanoidRootPart tells us which direction the NPC is currently looking or facing.
• Direction NPC is Moving:
  • The Velocity of the HumanoidRootPart tells us how fast and in what direction the NPC is moving.

When these two directions (facing and moving) are aligned, the NPC is moving straight. When they differ, the NPC is turning.

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2. How to Detect Turning

To determine whether the NPC is turning:

• Compare the direction the NPC is facing with the direction it is moving.
• A mathematical operation called the dot product measures how similar these two directions are:
  • A value close to 1 means the NPC is moving straight.
  • A value less than 1 means the NPC is turning.

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3. Breaking Down the Process

Step 1: Get the NPC’s Direction

• The direction the NPC is facing comes from the LookVector of its HumanoidRootPart.
• The direction it is moving comes from the Velocity.

Step 2: Check for Alignment

• If the facing direction (LookVector) matches the movement direction (Velocity), the NPC is moving straight.
• If not, the NPC is turning.

Step 3: Handle Special Cases

• If the NPC isn’t moving at all (its Velocity.Magnitude is 0), we don’t need to check for turning.
• Use a threshold to decide how “sensitive” the turning detection is.

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4. When to Use This Detection

This technique is helpful for:

• Adding custom animations when an NPC turns.
• Triggering events when an NPC changes direction (e.g., looking around a corner).
• Debugging NPC pathfinding behaviors.

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5. Optimizing for Performance

Roblox Studio is optimized for gameplay, but if you’re working with multiple NPCs, keep these tips in mind:

• Use Efficient Checks:
  • Only perform calculations when the NPC is moving (Velocity.Magnitude > 0).
• Avoid Overloading the Game:
  • Use Roblox’s RunService.Heartbeat event to check turning smoothly without slowing the game.
• Modularize Your Code:
  • Write separate functions to make your logic easy to understand and reusable.

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6. Roblox Studio Updates to Keep in Mind (2024)

Roblox continuously improves its platform, and here are some recent updates that may help:

• Better Performance:
  • Use new features like Parallel Luau to run NPC calculations faster.
• Enhanced Debugging Tools:
  • Roblox now offers better visualization tools to monitor NPC behavior in real-time.
• API Improvements:
  • Regularly check Roblox’s developer hub for updates to the Humanoid and HumanoidRootPart APIs.

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7. Summary

Here’s a simplified breakdown of what you’re doing:

• Compare the NPC’s facing direction (LookVector) with its movement direction (Velocity).
• Use the dot product to detect turning (values close to 1 mean straight movement, less than mean turning).
• Optimize for performance by only running checks when necessary and using the latest Roblox Studio tools.

By understanding these concepts, you can create smooth and responsive NPC behaviors for your game! Let me know if you want more tips or need help with anything specific.