Camera FOV seems incorrect

Bugs
1

I am trying to implement physically correct camera controls (based on lens size, focal length, and f-stop). However I noticed that the camera FOV in Babylon seems incorrect.

As a test, I created a simple scene in Blender (just a cube + light + camera) with a 35mm camera and 50mm focal length. This gives a FOV of 39.60.

However, when I import the GLB into Babylon, it has a FOV of 22.90. If I manually change the camera’s FOV to 39.60 then the result seems wrong (the perspective is slightly off, and the cube is too small).

Here is a sandbox which demonstrates the problem:

https://playground.babylonjs.com/#40ISEF

It overrides the FOV to the correct 39.60. If you comment out the camera.fov = ... line then you will see Babylon’s default FOV.

If I view the same GLB in https://gltf-viewer.donmccurdy.com/ then it has the correct FOV. You have to change the camera to “Camera_Orientation”.

So I see two bugs here:

  1. It is ignoring the FOV which is specified in the GLB file.
  2. When manually setting the correct FOV the result is incorrect.
2

For reference, here is what the FOV looks like in Blender (it’s the same as the GLTF viewer):

FOV Test
FOV Test1280×720 335 KB

3

Oh, it seems the editor was screwing up the size. If I remove the editor, then the FOV is correct.

And it seems that Babylon is importing the camera with a vertical FOV (whereas Blender uses a horizontal FOV), which is why the FOV is 22.90 and not 39.60.

So after some more testing, it seems Babylon is correct. Sorry for the noise.

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