# A 2D point projection on a 3D segment.

#### IhorV

##### New member
Hello everyone. So, there is a point in 2D space with known coordinates. Also, there is a segment in 3D space with known coordinates (both beginning and end). The point overlaps the segment. Is there a way to find 3D coordinates of the point's projection onto this segment?

#### Dr.Peterson

##### Elite Member
Huh? A 2D space and a 3D space are separate things. You seem to be assuming the former is in the latter.

Maybe you mean this: You are given a point P, say on the x-y plane, and a segment with known endpoints $$\displaystyle A(x_0, y_0, z_0)$$ and $$\displaystyle B(x_1, y_1, z_1)$$, and you want to project the point perpendicularly onto the line, and find the (x, y, z) coordinates of the projection.

It doesn't matter where the point is; it doesn't have to be on some particular plane in order to project it. Have you searched for information on projection onto a line?

I might do a vector projection of AP onto AB, and add the resulting vector to the location vector OA.

#### HallsofIvy

##### Elite Member
When you say "2D space" do you mean, say, the xy-plane in an xyz coordinate system?