If you're tired of using old BodyVelocity objects that don't quite work right anymore, switching to a roblox linear velocity script is definitely the way to go for modern physics. Roblox has been pushing their "Mover Constraints" for a while now, and honestly, they're way more stable than the legacy stuff we used to use back in the day. If you want to make a part move in a straight line—whether that's for a rocket, a dash mechanic, or a moving platform—LinearVelocity is your new best friend.
Why the old stuff doesn't cut it anymore
You might still see some old tutorials talking about BodyVelocity. While that still technically works (for now), Roblox has officially deprecated it. That's a fancy way of saying they aren't updating it anymore and it might eventually break. The new system, which includes the roblox linear velocity script, is built on the newer physics engine. It's much smoother and gives you more control over how forces are applied.
One of the biggest headaches with the old objects was how they interacted with other forces. They often felt "stiff." The newer LinearVelocity constraint feels more integrated with the world's physics. It respects things like friction and collisions a bit more predictably, which is great if you don't want your objects flying through walls at a thousand miles per hour because of a glitchy force calculation.
Getting the basic setup right
Before you even touch a script, you have to understand that LinearVelocity isn't just a property you toggle on a part. It's a constraint. This means it needs a couple of things to exist in the Explorer before it'll do anything at all.
Attachments are the secret sauce
Every LinearVelocity needs an Attachment. Think of an attachment as the specific "handle" on the part where the force is being applied. If you put the attachment in the very center of the part, the force pushes it right through the middle. If you put it on one of the edges, you might get some weird spinning if you aren't careful.
Usually, you'll just put an Attachment inside the Part you want to move. Then, you'll create the LinearVelocity instance and point its Attachment0 property to that attachment. Without this link, your roblox linear velocity script will just sit there doing absolutely nothing, which is a common mistake that drives people crazy.
Writing your first roblox linear velocity script
Let's look at a super simple way to get a part moving. You can do this all manually in the properties window, but if you're making a game, you probably want to trigger it via code.
Imagine you have a part in your workspace. Here's a basic script you could drop into a Script object to get things rolling:
```lua local part = script.Parent local attachment = Instance.new("Attachment") attachment.Parent = part
local linearVelocity = Instance.new("LinearVelocity") linearVelocity.Attachment0 = attachment linearVelocity.MaxForce = 10000 -- This needs to be high enough to move the weight linearVelocity.VectorVelocity = Vector3.new(0, 0, 50) -- Move forward on the Z axis linearVelocity.Parent = part ```
Breaking down the code
In that snippet, we're doing a few key things. First, we create the attachment and the velocity object on the fly. This is cleaner than making them manually if you're spawning items like bullets or spells.
The MaxForce property is where most people get stuck. If you leave it at the default, it might be too weak to move your part, especially if the part is large or heavy. Setting it to a high number like 10000 or even math.huge (if you want infinite force) ensures that the part actually reaches the speed you set in VectorVelocity.
Taking things further with relative velocity
One of the coolest things about a roblox linear velocity script is the RelativeTo property. By default, it's set to World. This means if you tell it to move at Vector3.new(0, 0, 50), it will always move toward the world's Z-axis, no matter which way the part is facing.
But what if you're making a car or a player dash? You want the part to move forward relative to itself. You can change RelativeTo to Attachment0. Now, if you rotate the part, the velocity rotates with it. If the "front" of your part is facing the sky, the script will blast it straight up. This makes making projectiles or movement abilities ten times easier than the old math-heavy ways.
Real-world examples you can use right now
Let's talk about some actual use cases. Just knowing how to move a block is one thing, but making a game mechanic is where it gets fun.
A quick dash mechanic
If you want to make your player zoom forward when they press a key, a roblox linear velocity script is perfect. You'd basically instance the velocity inside the player's HumanoidRootPart, set the VectorVelocity to their forward vector multiplied by a speed, and then use Debris service to remove it after a fraction of a second. It creates a snappy, professional-feeling movement.
Constant speed projectiles
For things like arrows or slow-moving magic orbs, you don't necessarily want gravity to pull them down immediately. You can set the LinearVelocity to a constant speed and set the MaxForce high enough that it resists gravity's pull. It's a lot more reliable than just setting the Velocity property once and hoping for the best.
Common headaches and how to fix them
Even with a solid roblox linear velocity script, things can go sideways. If your part isn't moving, the first thing to check is Anchored. An anchored part cannot be moved by physics constraints. It sounds obvious, but I've lost count of how many times I've spent twenty minutes debugging a script only to realize the part was anchored the whole time.
Another thing is the Massless property. If your part is incredibly heavy, you might need a ridiculous amount of MaxForce. Toggling Massless on the part can sometimes make the physics behave a bit more predictably when you're just starting out.
Also, keep an eye on your Constraints toggle in the Roblox Studio editor. If you can't see the little visual arrows for your velocity, it's hard to tell which way it's pointing. Turning on "Constraint Details" in the View tab is a lifesaver for visualizing where your force is actually going.
Wrapping it up
Using a roblox linear velocity script is basically a requirement for modern game dev on the platform. It's more robust, it's what the engine prefers, and it gives you much better control over relative movement. Once you get used to the workflow of "Part > Attachment > LinearVelocity," you won't ever want to go back to the old ways.
It might feel like an extra step to deal with attachments at first, but the flexibility you get in return is worth it. You can move things in world space, local space, or even relative to other parts. Just remember to watch your MaxForce values and make sure nothing is anchored, and you'll be making smooth, physics-based movement in no time.
Keep experimenting with the different properties, and honestly, the best way to learn is just to mess around with the numbers in a test place. See how fast you can make a part go before it clips through the floor—it's half the fun of game development anyway.