"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:
>
> > IIRC, it isn't what you think it might be, but half of that
>
> I think maybe this series of equation rearrangements might shed some light on
> the issue.
>
> From:
>
http://news.povray.org/povray.advanced-users/thread/%3Cweb.580f8b048d6e3073b488d9aa0%40news.povray.org%3E/
>
> // direction_length = 0.5 * right_length / tan(angle / 2)
> // tan(angle / 2) * direction_length = 0.5 * right_length
> // tan(angle / 2) = (0.5 * right_length) / direction_length
> // (angle / 2) = atan2( (0.5 * right_length), direction_length)
> // angle = 2* atan2( (0.5 * right_length), direction_length)

Thanks for the links and suggestions, they are quite useful.

However, my problem appears in all of the equations you mentioned. The problem
is of trigonometry nature. We have a triangle as depicted here
https://www.povray.org/documentation/view/3.6.1/246/ one side is
direction_length and one side is right_length (half of the view). Tangent
defines their ratio. Where does the "0.5" come from?

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