[3ds max] [unity] aspect ratio switching tricky problem

Rigging
#1

I’m working on a 3DS Max previs tool so artists can see their work as it would be framed on various mobile devices.
The Basic aspect ratios To support art 4:3 and 16:9.
unfortunately The way unity switches aspect ratios differs from the way 3DS Max does it.
The following Max screenshots explain it better than words can.

Starting with the 4:3 aspect ratio:

When Max changes to 16:9 image area is zoomed in to match the new width.
this effectively cuts off areas above and below relative to the 3:4 version

In unity, the image area is unchanged, the view simply expands to the sides

Basically, Max achieves 16:9 by squeezing the frame vertically, while unity expands the frame horizontally.

So…I’d like to force max to behave the unity way.
I’m pretty sure its a straight forward math issue
but I can’t math today.

#2

Most game engines maintain the Vertical FOV of the camera.
However, 3ds max retains the Horizontal FOV of the camera.

Setting the same Vertical FOV between aspect ratio changes should have the same behaviour as in Unity.

#3

thank you, that did the trick.

			
fn HDcam cam=(
	renderWidth =(renderHeight  as float *1.77778)
	cam.curFOV=35
)

fn SDcam cam =
(
	renderWidth =(renderHeight  as float *1.33333)
	cam.curFOV=35
)