Find world x and z position given screen position and world y position

Hi , I need to place a book on a table, so that, after projection, the book appears in the given screen position (xs, ys).

I already know the yw (y world coordinate) the book must have, and I need to find the xw and zw.

I also know xs and ys, the screen coordinates where the book must appear after projection.

In other words, I need to find xw and zw such that (xw, yw, zw) after projection becomes (xs, ys).
yw, xs and ys are known.

I don’t think I can use Camera.ScreenToWorldPoint because I don’t know the distance from the camera. This is what I need to find :slight_smile:

Could someone kindly explain how to find xw and zw? Thank you

a solution is to intersect the plane y = ys with the ray from the camera to the mouse position on screen (Camera.ScreenToRay).

I thought I had to solve an equation involving the projection matrix, but it is not needed. However it would be interesting to know how to do it.