The up vector $s$ we are given need not be orthogonal to $n,$ so we cannot use it as our

image's up vector $v.$ Instead, we must first compute hat$(u)$ orthogonal to $n$ and $s.$ Then, we

can compute hat$(v)$ from $n$ and hat$(u).$ Both hat$(u)$ and hat$(v)$ should be normalized. If we are standing at $e$

and looking at $c$ with $s$ pointing roughly upwards, then hat$(u)$ should be pointing to the right,

and hat$(v)$ should be pointing upwards. Make sure you check that these two vectors point in the

correct direction. Don't worry about their length yet.

Next, we scale hat$(u)$ to $u$ and hat$(v)$ to $v$ so that $||u||=w_p$ and $|v|=h_p.$ In this way, adding $u$

causes us to move right one pixel, and adding $v$ causes us to move up one pixel.

Find the bottom left corner $p.$