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nssampat

Could you explain this diagram? Why are we drawing this trapezoid-like shape to connect the origin to X instead of using similar triangles as before? What is Z_0?

motoole2

This illustration is admittedly a little odd to look at, because light does not behave this way! This diagram here conveys the idea that the model of a weak perspective camera can be approximated as imaging a (fronto-parallel) plane at a distance $Z_0$ from out camera. Points $X$ are orthographically projected onto this plane, by replacing points $[X,Y,Z]$ with $[X,Y,Z_0]$. For example, this is a good model to use when $Z_0$ is significantly larger than the $Z$ of our points, as shown in this slide.