math - How to calculate the z-distance of a camera to view an image at 100% of its original scale in a 3D space

Question

How can one calculate the camera distance from an object in 3D space (an image in this case) such that the image is at its original pixel width.

Am I right in assuming that this is possible given the aspect ratio of the camera, fov, and the original width/height of the image in pixels?

(In case it is relevant, I am using THREE.js in this particular instance).

Thanks to anyone who can help or lead me in the right direction!

Answer 1

Thanks everyone for all the input!

After doing some digging and then working out how this all fits into the exact problem I was trying to solve with THREE.js, this was the answer I came up with in JavaScript as the target Z distance for displaying things at their original scale:

var vFOV = this.camera.fov * (Math.PI / 180), // convert VERTICAL fov to radians

var targetZ = window.innerHeight / (2 * Math.tan(vFOV / 2) );

I was trying to figure out which one to mark as the answer but I kind of combined all of them into this solution.