If you've been scratching your head trying to figure out how to let users click and drag to pick an area in 3D space, this roblox studio plugin region selection tutorial should help you get it working without tearing your hair out. It's one of those things that seems simple until you actually start writing the code and realize you have to deal with mouse coordinates, 3D math, and visual feedback all at once. But honestly, once you break it down into a few manageable steps, it's actually pretty fun to build.
Why bother with custom region selection?
Let's be real for a second. The default tools in Roblox Studio are great, but sometimes they just don't cut it for specific workflows. Maybe you're building a terrain editor, a mass-object deleter, or a custom placement system. You need a way for the user to say, "Hey, everything inside this specific box is what I want to change."
That's where a region selection tool comes in. It gives your plugin that professional feel where a user can click, drag, and see a translucent box expanding in real-time. It's much more intuitive than typing in coordinates or clicking parts one by one.
Setting up your plugin environment
Before we dive into the heavy math, you've got to get your plugin structure ready. I'm assuming you already know how to save a script as a local plugin, but if not, you just right-click a folder or script in the Explorer and hit "Save as Local Plugin."
For this roblox studio plugin region selection tutorial, we need a few things: 1. A way to activate the tool (usually a button in the top bar). 2. A way to track where the mouse is in the 3D world. 3. A visual part that shows the selection area.
First, you'll want to use plugin:CreateToolbar and toolbar:CreateButton. When that button is clicked, you'll call plugin:Activate(true). This is super important because it tells Studio that your plugin is now taking control of the mouse and viewport. If you don't activate the plugin, you might find that your clicks are still selecting parts in the workspace instead of triggering your custom code.
Tracking the mouse and creating the box
The core of a region selection tool is the mouse. You can get the mouse object using plugin:GetMouse(). We're going to need two main points: where the user first clicks (let's call it the "Origin") and where the mouse currently is (the "End").
Here's a common trap: don't just use mouse.Hit.p. If the user clicks on the skybox, mouse.Hit can get a bit wonky. It's often better to use a Raycast from the mouse's 2D screen position into the 3D world, or just ensure you have a large baseplate to click on. For the sake of this tutorial, we'll assume you're clicking on surfaces.
When the Button1Down event fires, you store that first position. Then, you use a RunService.RenderStepped connection (or a Mouse.Move event) to constantly update the "End" position as the user drags their mouse.
The math behind the selection box
This is the part where people usually get stuck. How do you take two points in 3D space and turn them into a Part that looks like a box?
A Part in Roblox needs a Position (its center) and a Size. If you have Point A (where you clicked) and Point B (the mouse's current position), the math looks like this:
- Size: This is the absolute difference between the coordinates.
Vector3.new(math.abs(A.X - B.X), math.abs(A.Y - B.Y), math.abs(A.Z - B.Z)). - Position: This is the average of the two points.
(A + B) / 2.
When you apply these to a temporary Part in the workspace (let's call it the "SelectionBox"), it will perfectly stretch between your initial click and your cursor. Pro tip: make sure this part has CanCollide set to false, is Anchored, and has a bit of transparency so it doesn't get in the way or mess up your raycasting. You don't want the mouse to accidentally hit the selection box itself, or it'll start stuttering like crazy!
Handling the release
Once the user lets go of the mouse button (Button1Up), that's when the real magic happens. You've got your final "Origin" and "End" points, and your visual box is sitting there in the workspace. Now you need to find out which parts are inside that area.
In the old days, we used Region3, but Roblox has moved on to something much better: WorldRoot:GetPartBoundsInBox. This function is way more flexible. You just pass it the CFrame of your selection box and the Size of the box, and it returns a list of every part inside those bounds.
It looks something like this in your script: local partsInRegion = workspace:GetPartBoundsInBox(selectionPart.CFrame, selectionPart.Size, overlapParams)
You can use OverlapParams to filter out specific things, like ignoring the selection box itself or only looking for parts in a certain folder. It's incredibly efficient compared to the old methods.
Making it feel smooth
If you want your plugin to feel really polished, don't just stop at a basic box. Think about the user experience. For example, what happens if the user accidentally clicks the button but doesn't want to select anything? You should probably have a way to cancel the action, maybe by hitting the "Esc" key.
Also, consider the "Y" axis. When you're selecting a region on a flat map, do you want the box to be flat on the ground, or do you want it to have some height? A lot of plugins default the Y-size to something like 10 or 20 studs so it catches everything from the floor to the ceiling of a building. If you want a true 3D volume selection, you'll need to figure out a way to let the user define the height, perhaps with a second drag or by just using a fixed value.
Visual feedback and cleanup
Don't forget to clean up after yourself. Once the selection is made and you've gathered your list of parts, you should destroy or hide the selection box part. Leaving random translucent parts scattered around the workspace is a quick way to make users uninstall your plugin.
You might also want to highlight the parts that were selected. You can use the Selection service in Studio to actually select the parts in the Explorer, making it look like the user manually clicked them. game:GetService("Selection"):Set(partsInRegion) This is a small touch, but it makes the tool feel integrated into the native Studio environment.
Common pitfalls to avoid
One thing I see a lot in every roblox studio plugin region selection tutorial is forgetting about coordinate systems. If your selection box is rotated, GetPartBoundsInBox handles it fine, but calculating the size and position from two mouse points usually assumes an axis-aligned box (one that doesn't rotate). For most plugins, this is fine! Users expect the selection box to align with the global X, Y, and Z axes.
Another thing: performance. If you're running a loop that checks for parts while the user is dragging, keep it optimized. While GetPartBoundsInBox is fast, you don't necessarily need to call it 60 times a second just to show the visual box. Save the heavy lifting for the moment the user releases the mouse button.
Wrapping things up
Building a custom selection tool is a bit of a rite of passage for Roblox plugin developers. It forces you to get comfortable with the Plugin object, mouse input, and spatial queries.
The basic workflow is always the same: activate the plugin, capture the start point, update a visual part while dragging, and use a spatial query to find the parts when the drag ends. Once you've got that down, you can start adding fancy features like filters, grid snapping, or even circular selections if you're feeling adventurous with the math.
So, go ahead and give it a shot. It might take a few tries to get the CFrame and Size logic perfectly aligned, but once you see that box dragging smoothly across your viewport, it'll all be worth it. Happy coding!