Need quick Pol->Rec->Pol routine

Started by krazywest February 23, 2003 03:13 PM

0 comments, last by krazywest 22 years ago

Author

122

February 23, 2003 03:13 PM

Is there a nice quick (as in really quick) Polar to normal co-ordinates (and back again) routine? I have written one with sqrt(sqrt(sqrt(sqrt(sqrt(sqrt( etc. but its too slow.

http://www.fana.co.uk/

IainC

127

February 23, 2003 04:07 PM

Why yes

I''m using what I call "Siegielian" co-ordinates - the latitude (round the way) ranges from 0 to 2PI, and the longitude (up & down the way) from +1 to -1 (so 0 is the equator). You can easily scale these to your fancy.

So it''s not actually polar as in azimuth and elevation at all when I think about it... oh. Might not be what you actually wanted then!

Hope these help anyway...

The convention I use is phi for latitude, and z for longitude.

  void GetUnitCartesianFromSiegelian (float z, float phi, GLfloat *result) {	double theta = asin(z);	result[0] = (float)(cos(theta) * cos(phi));	result[1] = (float)(cos(theta) * sin(phi));	result[2] = z;}void GetSiegelianFromUnitCartesian (GLfloat *point, float *z, float *phi) {	*phi = (float)atan2(point[1], point[0]);	*z = point[2];}

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