Table of Contents
TL;DR
Raycasting in Roblox uses workspace:Raycast() to shoot invisible rays that detect collisions. Set up origin, direction, and RaycastParams to control behavior and get detailed hit information.
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What is Raycasting in Roblox?
Raycasting is a powerful technique that shoots an invisible ray from one point to another in your Roblox game world. Think of it like a laser pointer that can detect what it hits along its path. This ray travels in a straight line until it collides with an object or reaches its maximum distance.
Basic Raycasting Syntax
The core function you’ll use is workspace:Raycast(). Here’s the essential structure:
local raycastParams = RaycastParams.new()
local raycastResult = workspace:Raycast(origin, direction, raycastParams)Required Parameters
- Origin: A Vector3 representing where the ray starts
- Direction: A Vector3 showing the ray’s direction and length
- RaycastParams: Optional settings that control how the ray behaves
Setting Up RaycastParams
RaycastParams gives you fine control over your raycast behavior:
local raycastParams = RaycastParams.new()
raycastParams.FilterType = Enum.RaycastFilterType.Blacklist
raycastParams.FilterDescendantsInstances = {workspace.IgnoreFolder}
raycastParams.IgnoreWater = trueKey Properties
- FilterType: Use Blacklist to ignore specific objects, or Whitelist to only hit certain objects
- FilterDescendantsInstances: Array of objects to include/exclude based on FilterType
- IgnoreWater: Boolean that determines if the ray passes through water
Practical Example: Mouse Click Detection
Here’s a common use case – detecting what a player clicks on:
local Players = game:GetService("Players")
local UserInputService = game:GetService("UserInputService")
local player = Players.LocalPlayer
local mouse = player:GetMouse()
UserInputService.InputBegan:Connect(function(input)
if input.UserInputType == Enum.UserInputType.MouseButton1 then
local camera = workspace.CurrentCamera
local unitRay = camera:ScreenPointToRay(mouse.X, mouse.Y)
local raycastParams = RaycastParams.new()
local raycastResult = workspace:Raycast(unitRay.Origin, unitRay.Direction * 1000, raycastParams)
if raycastResult then
print("Hit:", raycastResult.Instance.Name)
print("Position:", raycastResult.Position)
print("Normal:", raycastResult.Normal)
end
end
end)Understanding Raycast Results
When your ray hits something, you get a RaycastResult object with useful properties:
| Property | Description |
|---|---|
| Instance | The part that was hit |
| Position | Exact Vector3 coordinates of the hit |
| Normal | Surface normal vector at the hit point |
| Distance | How far the ray traveled before hitting |
| Material | The material of the surface hit |
Common Raycasting Applications
Developers use raycasting for numerous gameplay mechanics:
- Weapon systems: Bullet trajectory and hit detection
- Ground detection: Checking if a character is standing on solid ground
- Line of sight: Determining if one object can “see” another
- Interaction systems: Detecting what players are looking at or pointing to
- Pathfinding: Obstacle detection for AI movement
Performance Tips
Raycasting can be expensive if overused. Keep these optimization strategies in mind:
- Limit raycast frequency using timers or event-based triggers
- Use shorter ray distances when possible
- Filter out unnecessary objects with RaycastParams
- Cache raycast results when the same information is needed multiple times
Master these raycasting fundamentals and you’ll unlock powerful detection capabilities that can enhance any Roblox experience you’re building.
Who this is for: Roblox developers learning collision detection, interaction systems, and advanced gameplay mechanics.
