#5960 - sgeos - Tue May 13, 2003 11:40 pm
As I've been doing trig posts recently, I decided I'd try to tackle background rotation. For the most part, it seems pretty straight forward, but what I worked out for magnification differs from Martin Korth's gbatek.
If I understand correctly, a, b, c, and d should correspond to PA, PB, PC, and PD when the BG is rotated A degrees. If we want h to have certain length, we solve for a like so:
cos A = a / h
h * cos A = a
If h is just as long as it was before rotation, then there is not any magnification. Should not setting the length of h specify the magnification? With minor modifications to avoid confusion with the above diagram, in the gbatek this is listed as:
PA = cos (A) / xMag
I really must have missed something. Why does dividing cos(A) by the magnification work?
-Brendan
| Code: |
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:A\ d : \i h _,-': :_ \/\R _,-' _: c :R| B\,-'A |R: ^^^^^^^^^^^^^^^^^^ b a |
If I understand correctly, a, b, c, and d should correspond to PA, PB, PC, and PD when the BG is rotated A degrees. If we want h to have certain length, we solve for a like so:
cos A = a / h
h * cos A = a
If h is just as long as it was before rotation, then there is not any magnification. Should not setting the length of h specify the magnification? With minor modifications to avoid confusion with the above diagram, in the gbatek this is listed as:
PA = cos (A) / xMag
I really must have missed something. Why does dividing cos(A) by the magnification work?
-Brendan