How convert the coorardinates of the mouse from one camera to another?

Let’s say I have 2 cameras one looking at a mesh with a render texture and another camera setup to the render texture. How would I convert the position clicked on the mesh with the render texture to the position of the second camera?
I have a picture to make my question clearer.

109361-camera-click-to-other-camera.png

You can use Camera.WorldToScreenPoint to convert the world position (where you clicked on the mesh) into the screen position on the second camera.

That’s a bit of a tricky question :

Imagine that your mesh with the render texture is a kind of portal to your second camera. What you need to do is to trace a ray from the first camera to to mesh, “transfer” this ray to the second camera, an continue it from there to the “real” mesh.

The second camera near plane corresponds to the mesh with the render texture.