I'm working on a 3D perspective game and it would help if you could answer this:
Plane $P$ is defined as: $xf \cdot x + yf \cdot y + zf \cdot z + G = 0$
I know point $p$ $(xp, yp, zp)$ and point $f$ $(xf, yf, zf)$, and they each lie on plane $P$.
$xf, yf, zf, G, xp, yp, zp$ are all known.
I am looking for some point $q$'s coordinates. Point $q$ lies on plane $P$. Angle pqf forms a right angle.
*NOTE *: $f$ is at the same height as $q$ ($zq = zf$) and $p$ is above $q$.
I tried to use the dot product rule as well as the intersection of three planes in order to find point q, but it seemed there were too many unknown variables (which doesn't make sense to me).
Please help! Thanks.