The subject is Pinhole Camera.
I've given a camera matrix $P = \begin{pmatrix} 1 & 0 & 0 & 0\\ 0 & 1 & 0 & 0 \\ 0 & 0 & 1 & 1 \end{pmatrix}$ and a 3D point $X_3 = \begin{pmatrix} 1 \\ 1 \\ -1 \\ 1 \end{pmatrix}$
After computing the projection of the 3D point (w/ homo coordinates) $X_3$ in the camera w/ the camera matrix, by $PX_3$, I got to $A = \begin{pmatrix} 1 \\ 1 \\ 0 \end{pmatrix}$ .
I'm asked to describe the geometric interpretation of $A$.
The point here contains $Z = 0$ which I'm trying to figure out its geometric interpretation. AFAIK, it should be a point in infinity or something like that. Any help is appreciated.
From wikipedia:
