mdw@git.distorted.org.uk Git - ssr/blob - StraySrc/Libraries/Sapphire/sh/fixedPt

   1 ;
   2 ; fixedPt.sh
   3 ;
   4 ; Provides fixed point operations such as trignometry
   5 ;
   6 ; © 1994-1998 Straylight
   7 ;
   8
   9 ;----- Licensing note -------------------------------------------------------
  10 ;
  11 ; This file is part of Straylight's Sapphire library.
  12 ;
  13 ; Sapphire is free software; you can redistribute it and/or modify
  14 ; it under the terms of the GNU General Public License as published by
  15 ; the Free Software Foundation; either version 2, or (at your option)
  16 ; any later version.
  17 ;
  18 ; Sapphire is distributed in the hope that it will be useful,
  19 ; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ; GNU General Public License for more details.
  22 ;
  23 ; You should have received a copy of the GNU General Public License
  24 ; along with Sapphire.  If not, write to the Free Software Foundation,
  25 ; 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  26
  27 ;----- Overview -------------------------------------------------------------
  28 ;
  29 ; Functions provided:
  30 ;
  31 ;  fxp_atan
  32 ;  fxp_pol
  33 ;  fxp_sin
  34 ;  fxp_cos
  35
  36                 [       :LNOT::DEF:fixedPt__dfn
  37                 GBLL    fixedPt__dfn
  38
  39 ; --- fxp_atan ---
  40 ;
  41 ; On entry:     R0 == x, in 16.16 fixed point form
  42 ;
  43 ; On exit:      R0 == arctan x, in degrees, in 16.16 fixed point
  44 ;
  45 ; Use:          Calculates arctan x, hopefully fairly swiftly. The
  46 ;               accuracy of the result is open to doubt, although
  47 ;               it's usually good to about 3 significant figures.
  48 ;               It uses a small lookup table and linear interpolation
  49 ;               to calculate the result.
  50
  51                 IMPORT  fxp_atan
  52
  53 ; --- fxp_pol ---
  54 ;
  55 ; On entry:     R0 == x coordinate
  56 ;               R1 == y coordinate
  57 ;
  58 ; On exit:      R0 == angle in degrees, in 16.16 form
  59 ;
  60 ; Use:          Calculates the angle a vector makes with the +ve x axis.
  61 ;               The angle is given in degrees, rather than radians,
  62 ;               although this isn't really overly significant; it just
  63 ;               makes it slightly easier to work with, because it's
  64 ;               bigger.
  65 ;
  66 ;               This routine uses the arctan table and linear
  67 ;               interpolation, so it's fairly quick, but the accuracy
  68 ;               of its results is restricted to about 3 significant figures.
  69
  70                 IMPORT  fxp_pol
  71
  72 ; --- fxp_sin ---
  73 ;
  74 ; On entry:     R0 == angle in degrees, in 16.16 form
  75 ;
  76 ; On exit:      R0 == sin of angle, in 16.16 form
  77 ;
  78 ; Use:          Calculates a sin of an angle with a degree of swiftness and
  79 ;               a lot less accuracy.
  80
  81                 IMPORT  fxp_sin
  82
  83 ; --- fxp_cos ---
  84 ;
  85 ; On entry:     R0 == angle in degrees, in 16.16 form
  86 ;
  87 ; On exit:      R0 == cos of angle, in 16.16 form
  88 ;
  89 ; Use:          Calculates a cos of an angle with a degree of swiftness and
  90 ;               a lot less accuracy.
  91
  92                 IMPORT  fxp_cos
  93
  94                 ]
  95
  96 ;----- That's all, folks ----------------------------------------------------
  97
  98                 END