# What is FOVx in this diagram?

a beginner game developer here. I have recently taken upon learning about 3D game development and I am stuck on a simple matrix problem.

The image is found from this article: http://www.codinglabs.net/article_world_view_projection_matrix.aspx

I am trying to represent this matrix in my code but I am not sure what precisely is meant by FOVx and FOVy. What is the difference and how would I represent this in my perspective matrix? I am not using any 3D api.

• FOV is Field Of View. – Anko Dec 30 '14 at 3:52
• I understand that part, but how do I get the x and the y? What is the difference? I thought the FOV was just an angle – toshko3331 Dec 30 '14 at 3:55
• It's two angles actually: one horizontal (the x component), one vertical (y). For example, to emulate human vision, you might want to have a camera that can "see" a somewhat greater horizontal angle than vertically. – Anko Dec 30 '14 at 4:06
• Ah thank you, that actually clarifies things a lot more. I always assumed that the FOV was just a single angle. – toshko3331 Dec 30 '14 at 4:12
• That's pretty much the extent of my knowledge on projection matrices though! :) If you figure out the rest (or if that actually answers the question; I can't really tell), it's totally OK to post answers on your own questions too. – Anko Dec 30 '14 at 4:17

## 1 Answer

Here's wiki on topic: Field of view in video games

X and Y angles can be set separately to allow for wide/tall views. For example if you need a panorama for 3 displays like so, with default FOVy, but 120 degrees FOVx:

• One information you might also want to provide is which unit you need to provide the FOV in when building a projection matrix. I think it is in radian. Is this correct? – Philipp Dec 30 '14 at 8:26
• It depends on math functions implementation. Usually they expect angles in radians, but that is not always so. – Kromster says support Monica Dec 30 '14 at 9:05
• Thank you, and in my implementation it is specifying the angles in radians. However, I just convert them to radians in the function itself so whomever is using the function can pass the angle in degrees. – toshko3331 Dec 30 '14 at 22:13