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Asked: 2026-05-29T05:29:52+00:00

I’m writing a 2D game using a wrapper of OpenGLES . There is a

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I’m writing a 2D game using a wrapper of OpenGLES. There is a camera aiming at a bunch of textures, which are the sprites for the game. The user should be able to move the view around by moving their fingers around on the screen. The problem is, the camera is about 100 units away from the textures, so when the finger is slid across the screen to pan the camera, the sprites move faster than the finger due to parallax effect.

So basically, I need to convert 2D screen coordinates, to 3D coordinates at a specific z distance away (in my case 100 away because that’s how far away the textures are).

There are some “Unproject” functions in C#, but I’m using C++ so I need the math behind this function. I’m extremely new to 3D stuff and I’m very bad at math so if you can explain like you are explaining to a 10 year old that would be much appreciated.

If I can do this, I can pan the camera at such a speed so it looks like the distant sprites are panning with the users finger.

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1 Answer

  1. Editorial Team

    Found the answer at:
    Wikipedia

    It has the following formula:

    To determine which screen x-coordinate corresponds to a point at Ax,Az multiply the point coordinates by:
    enter image description here

    where
    Bx is the screen x coordinate
    Ax is the model x coordinate
    Bz is the focal length—the axial distance from the camera center to the image plane
    Az is the subject distance.

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