Find world x and z position given screen position and world y position (185875)

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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

I have a tip here: Using Camera.ScreenToRay method, you can convert your screen position into a ray you can then use with Physics.Raycast, to cast against your table.This will result in a world point on that table, matching your xs and ys, because the ray was fired straight out. Put the book there and voila.

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1 Answer

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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.