My problem is not specific to Unity, it’s purely mathematics. It has to do with projections, vectors, barycentric stuff and other line equations.

So I have 3 points, **A**, **B** and **C**, which are not aligned in space.

**pA**, **pB** and **PC** are their respective vertical projections on the « floor » (the **xz** plane). As they are also not aligned, they form a triangle on an horizontal plane.

I need to move my **B** point on the **x** axis only, so that it belongs to the same vertical plane as **A** and **C**.

As a consequence, **pA**, **pB** and **PC** should now be aligned.

I’m sure there are plenty of ways to do that, such as calculating **pB**’s coordinates with line equations, but I’m not sure what would be the right and the simpliest way.

Thanx in advance to all mathematician heroes