{ RCSid: $Id: illum.cal,v 2.8 2003/02/22 02:07:23 greg Exp $ } { Coordinate computations for mkillum output. There are no arguments for the spherical case: il_alt - Altitude (1 to -1) for spherical coordinates il_azi - Azimuth (0 to 2*PI) for sphere For the hemispherical case, A1-A9 are the unit vectors for the hemisphere's coordinate system: il_alth - Altitude (1 to 0) for hemispherical coordinates il_azih - Azimuth (0 to 2*PI) for hemisphere } norm_rad(r) : if( r, r, r+2*PI ); il_alt = Dz; il_azi = norm_rad(Atan2(Dy, Dx)); il_alth = sq(-Dx*A7-Dy*A8-Dz*A9); il_azih = norm_rad(Atan2(-Dx*A4-Dy*A5-Dz*A6, -Dx*A1-Dy*A2-Dz*A3));