GLTFLoader: camera xfov calculation is wrong

[pjoe]

Description of the problem

xfov is not calculated correctly. As fov is an angle you can not just multiply aspect ratio, but should do something like xfov = atan(tan(yfov) / aspectratio) (see https://www.gamedev.net/forums/topic/203238-perspective---x---fov/?tab=comments#comment-2294951)

This conversion is done here: https://github.com/mrdoob/three.js/blob/dev/examples/js/loaders/GLTFLoader.js#L2356

Three.js version

• Dev
• r91

Browser

• All of them

OS

• All of them

[pjoe]

After more testing the right formula is:

xfov=2*Math.atan(Math.tan(yfov/2) * aspect)

[donmccurdy]

Thanks for the report! Looking at this now, I'm not sure why we convert to xfov at all... glTF provides yfov, or "The floating-point vertical field of view in radians", and the THREE.PerspectiveCamera constructor expects "Camera frustum vertical field of view" in degrees. So we should just convert directly from radians to degrees.

[pjoe]

Hah, that explains what I'm seeing ... double (or triple) checked that the xfov got calculated correctly, but scene still didn't look quite right :)

Should be very easy fix then.

[donmccurdy]

Opened #13646