# SetPrimaryPartCFrame loop anchored car

Helloo, I would like to know if there are any ways to tween an anchored model or move it in a way that gives the illusion that its tweened, I’m aware of the “Introduction to tweening” topic by colbert, I also read the bottom bit about how, even if you unanchor it, it seems anchored, the thing is, with the cars I’m using, they are anchored to begin with, so I need them to be anchored, would I in the script need to unanchor them and anchor them again after the tween? Moreover, I think with the a chassis, the car parts are auto welded together? Correct me if I’m wrong, the problem is that there are too many factors and things I need to look out for, I don’t know if it will work, will the car still function properly after the tween where I would have to unanchor all parts except the primary part? Or do I have to tween, maybe I could use something that looks as close to a tween as possible.

Sorry if this looks like just a bunch of jibberish but I hope at least some of you understand where I’m getting at here, that if I use tweening it may interfere with how the car looks or works or functions, thanks for your time!

I’m not sure what you mean so I’ll write 2 answers.

## How to tween with unanchored objects

The whole problem here is the physics engine will apply forces to it. A way we can negate that is by tweening is but before we tween it we disable it in the physics engine by setting its can collide property to false.

## How to tween anchored objects within a ellipse/path

First, ditch tweening and use linear interpolation at that point. We’d need to map our alpha to a range of -pi to pi cause thats the domain of an ellipse. Now if you have no idea what this means i’d recommend just using my Math++ module. It also has bezier curves but theres too many examples of those lol.

I’m not sure what you mean so I’ll write 5 replies.

1. How would I go about using linear interpolation to move the model? I’ve never heard that before ngl

2. Don’t get me wrong, I’m good at maths, but when you mix math and roblox, they just repel in my head, maybe I’ll get it later.

3. What has maths got to do with bezier curves, I thought bezier curves is used to easily make roads, this sounds dumb to a lot of you I know

4. Pi? Radius diameter 3.141593654 thingy? MINUS PI? I’m new to scripting, I appreciate the help buddy, but I don’t understand, am pro at some things, but some other things not so pro

5. This is a simpler way of saying the thing I’m looking for:
If tweening doesn’t help with the unanchor anchor situation, then what is the name of another thing I can use which is similar and how would I use it in my case?

Thank you for your help, very much appreciated!

In a sense linear interpolation is the act of changing a value to map within a domain of 0 to 1. So all you would do is do something like setprimarypartcframe and then tween its cframe

Sorry!

That is an application for bezier curves. For a more in-depth tutorial on them watch this

The reason I say map it to -pi to pi is because the domain of cosine and sine (the “functions” which are needed for the ellipse formula are in bounds of -pi to pi.) It represents half of a unit circle in a sense.

Again, your problem still doesn’t make sense. Have you considered following the devforum format?

OK, let’s start again, how would I use `SetPrimaryPartCFrame` in a loop to move the car to a certain position?