Camera matrix

In computer vision a camera matrix or (camera) projection matrix is a ${\displaystyle 3\times 4}$ matrix which describes the mapping of a pinhole camera from 3D points in the world to 2D points in an image.

Let ${\displaystyle \mathbf {x} }$ be a representation of a 3D point in homogeneous coordinates (a 4-dimensional vector), and let ${\displaystyle \mathbf {y} }$ be a representation of the image of this point in the pinhole camera (a 3-dimensional vector). Then the following relation holds

where ${\displaystyle \mathbf {C} }$ is the camera matrix and the ${\displaystyle \,\sim }$ sign implies that the left and right hand sides are equal up to a non-zero scalar multiplication.

...
Wikipedia