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Cousin Ricky <ric### [at] yahoo com> wrote:
> Doctor John posted this version in 2009:
>
> https://news.povray.org/4aa8db4e$1@news.povray.org
Ah, excellent. I needed different search terms.
> As these camera shift macros and discussions have been sitting on my
> computer completely uncomprehended for years, I cannot say whether the
> "Corrected silly mathematical error in vertical scaling" addresses
> Thomas's concerns.
Well me neither, but I figured it was a good place to start. I've made some
sort of sense of all of the stuff Doctor John did, and so understand the WHY and
resulting output of what he does, and a little over half of the HOW.
The thing I do NOT understand is the purpose of the VCorr term or the meaning of
it's defining equation.
This is what I've got so far:
#local VCorr = pow(vlength(CamDirVec), 2) / pow(HypoXZ, 2);
// HypoXZ / CamDirVec = adjacent / hypotenuse = cos (theta)
// CamDirVec / HypoXZ = the inverse of the above, which is 1/cos (theta) = sec
(theta)
// Squaring numerator and denominator is the same as squaring the fraction
// so it looks like he's [erroneously?] calculating the secant squared of
theta
But maybe there's some trigonometric identity or other way of approaching the
meaning of the terms that sheds some light on what's going on....
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