Question Object following a spline at distance

I would like to have different GameObjects following a spline, but at a given distance. Like on the drawing below where my spline is in red, and I want the boxed GameObjects to follow the same path at the same distance they had initially from the spline. The left boxes should reach the end before the right ones because path is shorter there.

 

Okay and what part are you having trouble with?

You really just need a spline package first, such as Unity's one: https://docs.unity3d.com/Packages/com.unity.splines@2.4/manual/getting-started-with-splines.html

Off the top of my head, I would define the main spline, then calculate some points offset from the spline's start/end/other points along it. Then you can use those to calculate their own spline paths, and just use the API to make an object follow said spline.

 

This can be tricky. What you will need to do is some kind of a solver to ensure that the offset paths are truly traversed at a higher rate than the core path.

By solver I mean you would move ahead the correct amount on the spline, see how much the "beside" object moved, then adjust the spline motion up a bit, down a bit, hone in on it with a binary search basically.

Keep in mind splines can be arbitrarily tangled, so technically the naive "follow beside" position could even go backwards for portions of the inside of a very tight turn.

 

Thanks. I started investigating this option. Where I am struggling, is that I parse each knot on the spline, and now need to evaluate the tangent of this knot. However the spline.Evaluate function (which gives this tangent) requires as first argument a number between 0.0 and 1.0; How can I find this number from the knot ? ie if I take first knot, number is 0.0, last knot is 1.0, but intermediate knots ? I assume it's not 0.25, 0.5 and 0.75, because knots maybe be close to each other.
Thanks !

 

See my comment: you need a solver to find this.

 

Thanks. Solver concept for spline is unknown to me (only known for Physics). Any guidance for me ?

 

Generally a solver is used to evaluate a non-linear function by subdivided guessing.

Google for stuff like "bezier curve by distance" for what I mean. You can usually just take someone else's and hack it, then test it to make sure it works.