Focal length unitscomparison

Here the direction of those rays is reversed - instead of light flowing from the focal point onto the image plane where it hits a sensor/film to be detected & recorded in an image, instead light shines from the image plane on the monitor into the focal point of the viewer's eye. But the trigonometry works out similarly in each case.

where v is my 3D vector in homogenous coordinates. R is a 3x3 rotation matrix, t is a 3x1 translation vector, and K is a 3x3 "camera matrix". The camera matrix takes the following form

Focal lengthof lens formula

But I fundamentally don't understand what it means to express focal length in terms of pixels. In a real camera it's the physical distance between the imaging plane and the focal point of the lens, but there's no such analog in 3D graphics.

FOV tofocal lengthcalculator

Where's the focal point, the place where the rays connected our image plane converge/cross over at a point? The player's eye.

Why is it measured in pixels? Because that's the dimension you've chosen to measure your image plane. A monitor with square pixels of a particular resolution also has a particular dimension in real-world space, giving us an exchange rate between image units like pixels and real-world spatial units like cm. So you can think of the distance between the viewer & monitor being measured in cm and converted to pixels using assumptions about a typical monitor.

f is the "focal length" of the virtual camera and cx, cy is the "principal point" in pixels (usually the center of the screen).

Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

What isfocal lengthof lens

Both individuals and organizations that work with arXivLabs have embraced and accepted our values of openness, community, excellence, and user data privacy. arXiv is committed to these values and only works with partners that adhere to them.

arXiv Operational Status Get status notifications via email or slack

I am working on a renderer of sorts and I have some fundamental questions. Let's say I have a vector in a 3D virtual world space which is unitless, and I want to project it onto a 2D screen, so I need its pixel position.

So, assuming my camera is at the origin (and static), [R | t] moves the 3D vector v somewhere in front of the camera and I get some v'. Now, I want to project 3D vector v' onto the screen.