If you've been struggling to get your roblox studio prismatic constraint slide moving without it glitching out, you aren't alone. It's one of those tools that seems straightforward until your sliding door flies across the map or refuses to move an inch. Most developers run into issues with constraints because the physics engine in Roblox can be a bit picky about how things are aligned. But once you get the hang of it, you'll realize it's actually the most reliable way to handle linear motion—way better than just trying to script the CFrame of a part every frame.
The basics of setting things up
Before you jump into the properties panel, you need two parts. Let's call them the "Base" and the "Slider." The Base is usually the part that stays still—like a wall or a floor—and the Slider is the part you want to actually move. For a roblox studio prismatic constraint slide to function, the Base really should be anchored. If it isn't, the force of the slider moving might just push your whole assembly around like a shopping cart with a bad wheel.
The Slider, on the other hand, must be unanchored. This is a common mistake. If you anchor the sliding part, the physics engine just ignores the constraint entirely. It's like trying to pull a car that has its parking brake welded shut. Once you have those two parts, you'll head up to the "Model" tab, click the "Constraints" dropdown, and pick the Prismatic constraint. You'll click the Base first, then the Slider. This automatically creates the constraint object and two Attachments.
It's all about the attachments
The secret sauce to a working roblox studio prismatic constraint slide isn't the constraint itself; it's the orientation of the Attachments. When you look at an Attachment, you'll see some colored arrows. The yellow arrow (the WorldAxis) is the one that matters most here. The Prismatic constraint only allows movement along that yellow axis.
If your slider is supposed to go left and right, but your yellow arrows are pointing up, your part isn't going anywhere. Or worse, it'll try to move sideways, realize it can't, and start jittering like it's had too much coffee. You need to use the Rotate tool to make sure the yellow arrows on both Attachment0 (on the Base) and Attachment1 (on the Slider) are pointing in the exact same direction. If they're even a little bit off, the physics engine will fight itself, and your slide will feel "crunchy" or just get stuck.
Actuators and making it move
By default, a roblox studio prismatic constraint slide is just a "free" slide. It's like a curtain rod; if you push it, it moves, but it won't move on its own. To make it move automatically, you have to change the ActuatorType in the PrismaticConstraint properties.
You've basically got two main choices here: Motor and Servo.
A Motor is great if you want constant movement. Think of a conveyor belt or a sliding platform that just goes back and forth forever. You set a target velocity, and it just tries to hit that speed. It's simple, but it's not very precise if you want the slide to stop at a specific door frame.
A Servo is what you'll probably use most often. It's designed for precision. You tell the Servo, "Hey, go to position 10," and it'll move there and stop. This is perfect for sliding doors, elevators, or drawers. You just have to make sure the ServoMaxForce is high enough to actually move the weight of your part. If your part is a massive 50x50 block of granite and your force is set to 1000, it's not going to budge.
Setting the limits
You probably don't want your roblox studio prismatic constraint slide to keep sliding into infinity. To stop the slider from flying off the end of the rail, you need to enable LimitsEnabled.
When you toggle this on, you'll see two new properties: LowerLimit and UpperLimit. These are measured in studs relative to the position of Attachment0. It's usually a bit of trial and error to get these numbers perfect. I usually set them to something like -5 and 5 to start, then look at the green lines in the viewport to see where the boundaries are. If the slide hits these limits and bounces back too hard, check the Restitution setting. Setting that to 0 will make the stop feel solid, while a higher number will make it "bouncy."
Dealing with collisions and friction
One thing that drives people crazy is when the roblox studio prismatic constraint slide seems to get caught on invisible geometry. If your sliding part is physically touching the base part, the friction might be too high for the motor to overcome.
You have a few ways to fix this. You could make the parts not touch at all, leaving a tiny gap. Or, you can use a NoCollisionConstraint. Just select both parts, hit the NoCollisionConstraint button, and they'll pass through each other like ghosts while the Prismatic constraint still keeps them aligned. This is usually the cleanest way to do it because it lets you build tight-fitting mechanical parts without the physics engine freaking out over every little rub and bump.
Scripting the slider
Once the physical setup is done, you'll likely want a script to trigger the movement. Since we're using a Servo for our roblox studio prismatic constraint slide, it's incredibly easy to code. You don't need complex loops.
If you have a ProximityPrompt on a door, your script might look something like this:
```lua local constraint = script.Parent.PrismaticConstraint local open = false
script.Parent.ProximityPrompt.Triggered:Connect(function() if open then constraint.TargetPosition = 0 else constraint.TargetPosition = 8 -- Or however wide the door is end open = not open end) ```
It's that simple. Because the constraint handles all the physics, you don't have to worry about the door getting stuck if a player stands in the way—it'll just push them (assuming your ServoMaxForce is high enough) or stop if it hits an obstruction, just like a real door.
Troubleshooting the "Jitters"
If your roblox studio prismatic constraint slide starts shaking violently, it's almost always a conflict between two things. Maybe you have another constraint (like a Weld) accidentally holding the part in place. Or maybe the parts are colliding in a way that creates a physics loop.
Another common culprit is the LinearResponsiveness. If this value is too high, the Servo tries to correct the position so fast that it overshoots, then tries to correct back, creating a vibration. Lowering the responsiveness or tweaking the ServoMaxAcceleration can usually smooth that right out. Also, make sure your parts aren't "Massless" if you want them to behave predictably with physics, though sometimes toggling Massless on the slider can actually help if the part is unnecessarily heavy.
Why use Prismatic over Tweens?
A lot of new devs just use TweenService for everything. While Tweens are great for UI or things that don't interact with players, a roblox studio prismatic constraint slide is way better for gameplay elements. If a player jumps on a sliding platform moved by a Tween, they'll often just slide off because the platform isn't actually "pushing" them—it's just being teleported a tiny bit every frame.
With a Prismatic constraint, the motion is part of the physics world. If the platform moves, it carries the player with it. If it hits a crate, it knocks the crate over. It feels much more "real" in the context of a game. Plus, it's generally more performant for the server to handle these physics calculations than it is to have a bunch of scripts constantly updating CFrames.
Setting up a roblox studio prismatic constraint slide might take an extra minute compared to a simple weld, but the result is a much more professional and interactive feel for your game. Just remember: check your anchors, align your yellow arrows, and don't be afraid to crank up that MaxForce!