Setting up a roblox align position script constraint is one of the most reliable ways to handle physical movement in your game without things getting jittery or breaking the physics engine. If you've ever tried to move a part by manually updating its CFrame every single frame, you probably noticed that it doesn't interact very well with other objects. It kind of just ghosts through them or teleports around. That's exactly where AlignPosition saves the day, because it lets the physics engine do the heavy lifting for you while still giving you total control over where a part ends up.
What makes this constraint so useful?
Before we get into the actual code, it's worth talking about why we even use this thing instead of just anchoring a part and moving it. In Roblox, an anchored part is basically "dead" to the physics engine—it doesn't care about gravity, collisions, or momentum. But if you want a floating platform, a pet that follows a player, or a hovering drone, you usually want that object to be unanchored so it can bump into things or react to the world.
The roblox align position script constraint acts like a super-smart invisible rubber band. It pulls a part toward a specific goal position but does it using force. This means if the part hits a wall on its way to the destination, it'll actually stop or slide along the wall instead of just clipping through it. It feels much more "real" to the player.
Setting up the attachments
To get an AlignPosition working, you generally need two things: Attachment0 and Attachment1. Think of Attachment0 as the "hook" on the object you want to move, and Attachment1 as the "target" or the "anchor point" it's trying to reach.
When you're doing this via a script, you have to be careful about where you parent these things. Usually, you'll put Attachment0 inside the part you're moving. Attachment1 can be inside a different part (the goal) or even inside the same part if you're using "one attachment mode" (which we'll get to in a bit).
Most people start with the two-attachment setup because it's easier to visualize. You move Attachment1 to where you want the part to go, and the AlignPosition constraint will try its hardest to make Attachment0 overlap with Attachment1.
Writing the basic script
Let's look at how you'd actually write a roblox align position script constraint setup from scratch. You don't want to just drag and drop these in the editor every time; knowing how to spawn them via code is way more powerful.
```lua local movingPart = script.Parent -- The part we want to move local goalPart = workspace.TargetPart -- The place we want it to go
-- Create the attachments local att0 = Instance.new("Attachment") att0.Name = "MovingAttachment" att0.Parent = movingPart
local att1 = Instance.new("Attachment") att1.Name = "GoalAttachment" att1.Parent = goalPart
-- Create the AlignPosition constraint local alignPos = Instance.new("AlignPosition") alignPos.Attachment0 = att0 alignPos.Attachment1 = att1 alignPos.MaxForce = 10000 -- How strong the pull is alignPos.Responsiveness = 20 -- How fast it reacts alignPos.Parent = movingPart ```
In this snippet, we're basically telling the engine: "Hey, take this movingPart and try to shove it toward the goalPart." If you move the goalPart around in the workspace while the game is running, you'll see the movingPart follow it like it's attached by an invisible spring.
One attachment mode vs. two attachments
Now, sometimes you don't want to have a physical "goal part" sitting around in your workspace. Maybe you just want a part to follow your mouse cursor or fly toward a specific Vector3 coordinate. This is where "One Attachment Mode" becomes a lifesaver.
When you set the Mode property of your AlignPosition to Enum.PositionAlignmentMode.OneAttachment, you don't need an Attachment1 anymore. Instead, you just set the Position property of the constraint directly. This is great for scripting because you can just update alignPos.Position = myVector3 in a loop or a signal, and the part will head toward that coordinate. It keeps your workspace way cleaner since you aren't spawning dummy parts just to act as targets.
Tweaking the MaxForce and Responsiveness
This is where most people get tripped up. If your part isn't moving, or if it's flying off into space like a rocket, it's probably because of the MaxForce or Responsiveness settings.
MaxForce is exactly what it sounds like. It's the limit on how much power the constraint can use to move the part. If you're trying to move a massive, heavy boulder and your MaxForce is only 100, the boulder isn't going to budge. Often, for things like pets or small floating objects, developers just set this to math.huge (which is basically infinity) so the part never gets stuck. But be careful—if the part gets wedged in a corner with infinite force, it might start glitching out.
Responsiveness is a bit more subtle. It controls how "snappy" the movement is. A high responsiveness (like 200) will make the part jerk toward the target instantly. A low responsiveness (like 5 or 10) will make it feel floaty and smooth, almost like it's drifting through water. If you're making a drone, you probably want a lower responsiveness so it feels like it has some weight and momentum.
Handling the RigidityEnabled property
There's a checkbox called RigidityEnabled that basically ignores the Responsiveness setting and tries to move the part to the target as fast as physically possible. It's almost like a hard-weld but with physics. Personally, I don't use this much because it takes away that nice smooth transition, but if you need something to be pixel-perfect and don't care about the "swing" or "drift," it's there for you.
One thing to keep in mind is that if you enable Rigidity, you can't really fine-tune the feel of the movement anymore. It's either there or it isn't.
Common mistakes and how to fix them
If you've set up your roblox align position script constraint and it's just sitting there doing nothing, check these three things first:
- Is the part anchored? This is the classic "facepalm" moment for every Roblox dev. If the part you're trying to move is anchored, physics constraints won't do anything to it. Uncheck "Anchored" in the properties.
- Is the MaxForce too low? If your part is heavy (has high density) or is being blocked by gravity, a low MaxForce won't be enough to lift it. Try cranking it up to a huge number just to see if it starts moving.
- Are the attachments correct? Make sure
Attachment0is actually assigned to the part that's supposed to move. If you swap them by accident, you might end up trying to pull the entire world toward your small part, which obviously won't work.
Another weird thing that happens is the "spinning out of control" bug. AlignPosition only controls where the part is, not which way it's facing. If you want your part to stay upright or look in a certain direction, you'll need to pair the AlignPosition with an AlignOrientation constraint. They're like the peanut butter and jelly of Roblox physics—you almost always want them both.
Practical Example: A simple hover pet
Let's say you want a little floating cube to follow the player's shoulder. You'd use a script to constantly update the target position of an AlignPosition constraint.
You would get the player's Character, find the RootPart, and then calculate an offset (like 2 studs back and 2 studs up). Then, you'd feed that position into your roblox align position script constraint. Because it's a physical constraint, the pet will smoothly bob up and down as the player runs, and if the player walks through a narrow door, the pet will actually bump into the doorframe instead of just phasing through the wall. It adds a ton of polish for very little extra work.
Closing thoughts on physics constraints
Using a script to manage your constraints is definitely the way to go once your game gets a bit more complex. It gives you the ability to turn forces on and off, change targets on the fly, and adjust how heavy an object feels depending on what's happening in the game.
The roblox align position script constraint is a bit more work than a simple "Part.Position = Vector3," but the results look so much more professional. It handles the interpolation, the collisions, and the velocity math for you. Once you get the hang of the attachment system and the force settings, you'll probably find yourself reaching for it whenever you need to move something in your game world. Just remember to keep an eye on those MaxForce values and always make sure your parts are unanchored!