If you're trying to build anything interactive, like a gun system or a custom placement tool, you're going to need a solid roblox raycasting script to handle the heavy lifting. Raycasting sounds like some high-level math concept that only engine developers understand, but in reality, it's just a way of telling the game to "point a laser in this direction and tell me what it hits." Whether you're a seasoned scripter or just starting to mess around in Studio, getting a handle on rays is probably the biggest "level up" you can get.
How raycasting actually works in Roblox
Before we jump into the code, let's talk about what's actually happening. Think of a raycast as an invisible, infinitely thin line that starts at one point (the origin) and travels in a specific direction for a set distance. As soon as that line touches a part, the script stops and sends back a bunch of useful data.
It tells you where it hit, what part it hit, the material of that part, and even the "Normal," which is basically just a fancy word for which direction the surface is facing. If you've ever wondered how developers make bullet holes appear perfectly flat on a wall, they're using that Normal data. It's super handy once you get the hang of it.
Setting up a basic raycast
The most common way to write a roblox raycasting script nowadays is using the workspace:Raycast() method. In the old days, we had some older functions that were a bit of a headache, but the modern way is much cleaner and more efficient.
Here is a very simple example of how you might set one up:
```lua local origin = Vector3.new(0, 10, 0) local direction = Vector3.new(0, -20, 0)
local result = workspace:Raycast(origin, direction)
if result then print("We hit something!") print("Part name: " .. result.Instance.Name) print("Position: ", result.Position) else print("The ray didn't hit anything.") end ```
In this snippet, we're starting the ray at a specific point in the air and pointing it straight down. If there's a floor or a part underneath that point, the script will catch it. If not, the result will be nil, which is why we always use an if result then check before trying to do anything with the data. If you don't, your script will probably throw an error and stop working the moment you miss a shot.
The biggest mistake: Direction vs. Position
I see this all the time on the forums. A lot of people think the "direction" argument in a roblox raycasting script should be the position of the target. It's a totally logical mistake to make, but it's not how the math works.
The direction is actually a vector that tells the ray how far to travel from the origin. If you want a ray to go from Point A to Point B, you don't just put Point B's position in the direction slot. You have to subtract Point A from Point B.
It looks like this: local direction = targetPosition - origin.
If you just put the target position as the direction, your ray is going to end up pointing toward the world origin (0, 0, 0) relative to your starting point, and you'll be pulling your hair out wondering why your bullets are flying in random directions.
Using RaycastParams to filter things out
Most of the time, you don't want your ray to hit everything. If you're making a gun script, you definitely don't want the bullet to hit the player who is firing the gun. That's where RaycastParams comes in. It's basically a settings folder for your ray.
```lua local params = RaycastParams.new() params.FilterDescendantsInstances = {script.Parent} -- Ignore the gun or the player params.FilterType = Enum.RaycastFilterType.Exclude
local result = workspace:Raycast(origin, direction, params) ```
By setting the FilterType to Exclude, you can give the script a list of objects to completely ignore. This is essential for things like NPCs where you want the AI to see "through" its own body parts, or for transparent glass that shouldn't block a specific type of sensor. You can also use Include if you want a ray that only detects specific parts, like a "wall-only" detection system.
Making it practical: A simple laser pointer
Let's say you want to make a part that points a laser at the mouse. You'd combine the player's mouse position with a roblox raycasting script to find out where they're looking.
You'd get the mouse position from a LocalScript, fire a RemoteEvent to the server (since you usually want rays to happen on the server for security), and then cast the ray from the gun's barrel toward that mouse position.
One thing to keep in mind is that the mouse's Hit.Position is already the result of a raycast that Roblox does automatically. If you're doing something more complex, like a shotgun with a spread, you'll be doing multiple raycasts with slightly randomized direction vectors. It's all just basic math once you get the logic down.
Visualizing your rays
Since rays are invisible, debugging them can be a nightmare. You might think your script is broken when, in reality, your ray is just 0.1 studs too short or pointing slightly to the left.
A good trick I use is to create a temporary "debug part." When the ray hits something, I spawn a small, bright red neon sphere at result.Position. It helps you see exactly where the game thinks the hit happened. Or, even better, you can draw a long thin part that stretches from the origin to the hit position to act as a visual tracer.
Just remember to delete these parts after a second or two, or you'll quickly fill your workspace with thousands of tiny red dots and lag your game into oblivion.
Performance considerations
You might be worried that doing all this math will slow your game down. The good news is that raycasting is actually incredibly fast in the Luau engine. You can run hundreds, even thousands of rays per second without a massive performance hit, provided you aren't doing anything crazy like casting 10,000 rays every single frame on the client.
That said, you should still be smart about it. Don't raycast from every single part in your game if you don't have to. Only run the code when an action is triggered—like a player clicking their mouse or an NPC entering a "combat state."
Why you should use raycasting instead of Touched events
A lot of beginners rely on the .Touched event for things like bullets or melee weapons. While .Touched is fine for simple things like a lava floor, it's notoriously unreliable for fast-moving objects. Sometimes a bullet travels so fast that it passes completely through a wall between two frames, and the .Touched event never even fires.
A roblox raycasting script doesn't have that problem. Because it calculates the path instantly, it doesn't matter how fast the "object" is supposed to be moving. It checks the entire path at once, ensuring that if something was in the way, it gets caught. This is why almost every high-quality combat game on Roblox uses raycasting for its hit detection.
Wrapping things up
Mastering the roblox raycasting script is really just about getting used to vectors and the RaycastParams API. Once you stop fearing the math and start looking at rays as just "probes" you send into the world, you'll find that you can build much more complex systems.
From checking if a player is standing on the ground to creating complex AI that can navigate around obstacles, raycasting is the backbone of interaction in Roblox. It takes a bit of practice to get the directions right, and you'll definitely mess up the math a few times, but that's just part of the process. Keep tweaking your vectors, use your debug parts, and you'll be making pro-level systems in no time.