On Thu, 26 Jun 2003, Cyrille Henry wrote:
adding 2 spherical vector element by elements does not output the same result.
No, it certainly does not. Adding spherical vectors like that has a different meaning from usual addition, and frankly, I don't see how that can be useful anywhere. If you want to do linear (cartesian) addition, you have to get back into linear coordinates, add, and convert back to spherical coordinates; or else, if there is a shortcut, it's quite complicated.
The opposite, assuming linear coordinates, and then making a switch to spherical/cylindric when necessary, is what makes most sense to me. Especially because _then_ there are many shortcuts that you can take: e.g. you can do rotation in linear coordinates using almost only multiplications and additions.
From personal experience, I'd say that spherical coordinates aren't so
useful, but linear coordinates are *very* much so.
Mathieu Bouchard http://artengine.ca/matju