Rhino Camera Film Size


#1

Hi,

I want to know the Film size(width and height) of the Camera used in Rhino, in order to convert the lens length to field of view. Where can I find that info?
Thanks.


#2

It’s based on 35mm (classic) film, so that would be 36mm x 24mm (proportionally). If you draw a 36 x 24 rectangle, then a line normal from the center of the rectangle whose length corresponds to the focal length of the lens, then measure the angle from the lens focal point to diagonal corners of the rectangle, that should give you the FOV of the lens. For example a 50mm lens length in Rhino will give you a FOV of 46.793°

–Mitch


#3

I should add, however, that Rhino viewports can be proportioned other than the 3:2 ratio of 35mm film, so you may “see” more or less than the theoretical 35mm camera does in one direction.

–Mitch


#4

The minimum “film gate” in Rhino will always be 24mm, to get your other dimension, multiply by the viewport aspect ratio (can be found using -viewportProperties). So if you have a view port that is 1000x563, that is an aspect of 1.77 (or 16:9). So 24 * 1.77 = 42.6mm.

This may also help: http://wiki.mcneel.com/rhino/rhinolensing

What are you looking to do with this info? I ask because we have cobbled together some scripts and toolbars to get the correct lensing for different kinds of cameras (mostly motion picture), which may be of use to you.

Sam


#5

Thank you very much Helvetosaur and Sam​​Page for the nice explanations.

@SamPage - We are exporting fbx files from Rhino to Unity along with different camera view info. So I need to convert lens length in Rhino to FOV(vertical) in Unity. I’m using this formula, FOV = 2 arctan (x / (2 f)) and wanted to know the film size in order get the value of X. For now I think I can assume 3:2 aspect ratio. But if it get complex your scripts will be really helpful. If you don’t mind please share the scripts. Thanks.


#6

Hearing what you want to do, I’m not sure the scripts would be of much use to you, as they only modify the Rhino lens to fake a lens on a different camera body. I will attach it though in case there is something that you might be able to strip out of there to use yourself (like aspect ratio):

Cam_Lens_091013.rvb (8.0 KB)

I would be careful about this assumption. When people give a FOV of a lens, they most often are referring to the horizontal FOV. Due to most screen sizes, I would guess that most people have viewports that are wider than tall. This means that the film gate dimension that is most likely “right” (being 24mm) is the height, the width being variable depending on the aspect ratio. So the FOV (horizontal) of a Rhino lens can be constantly changing depending on the aspect ratio without ever changing the lens length.


#7

Thanks :smile:

In Unity they use the Vertical FOV. Not the horizontal FOV. So I’m taking the value that comes from that formula as Vertical FOV. I’m setting the Diagonal film size as the X value.
For 3:2 for a 50mm lens length the FOV 46.793°, is it horizontal or Vertical?


#8

Diagonal…


#9

@Helvetosaur - Do you mean it’s called Diagonal FOV?


#10

No, I meant that the diagonal FOV is 46.793°. The vertical FOV for a 36 x 24 frame is 26.991°. (for a 50mm lens)

–Mitch


#11

Thanks Mitch. It’s clear now. :smile: