sys/src/libdraw/icossin2.c

   1 #include        <u.h>
   2 #include        <libc.h>
   3 #include        <draw.h>
   4
   5 /*
   6  * Sine and Cosine of arctangents, calculated by
   7  *   (sin(atan(index/100.0))*1024.+0.5)
   8  *   (cos(atan(index/100.0))*1024.+0.5)
   9  * To use, get rational tangent between 0<=tan<=1, scale by 100,
  10  * and look up sin and cos, and use linear interpolation.  divide by 1024.
  11  * Maximum error is 0.0020.  Without linear interpolation, it's 0.010.
  12  */
  13 static
  14 short sinus[] = {
  15         0,      /* 0.00 */
  16         10,     /* 0.01 */
  17         20,     /* 0.02 */
  18         31,     /* 0.03 */
  19         41,     /* 0.04 */
  20         51,     /* 0.05 */
  21         61,     /* 0.06 */
  22         72,     /* 0.07 */
  23         82,     /* 0.08 */
  24         92,     /* 0.09 */
  25         102,    /* 0.10 */
  26         112,    /* 0.11 */
  27         122,    /* 0.12 */
  28         132,    /* 0.13 */
  29         142,    /* 0.14 */
  30         152,    /* 0.15 */
  31         162,    /* 0.16 */
  32         172,    /* 0.17 */
  33         181,    /* 0.18 */
  34         191,    /* 0.19 */
  35         201,    /* 0.20 */
  36         210,    /* 0.21 */
  37         220,    /* 0.22 */
  38         230,    /* 0.23 */
  39         239,    /* 0.24 */
  40         248,    /* 0.25 */
  41         258,    /* 0.26 */
  42         267,    /* 0.27 */
  43         276,    /* 0.28 */
  44         285,    /* 0.29 */
  45         294,    /* 0.30 */
  46         303,    /* 0.31 */
  47         312,    /* 0.32 */
  48         321,    /* 0.33 */
  49         330,    /* 0.34 */
  50         338,    /* 0.35 */
  51         347,    /* 0.36 */
  52         355,    /* 0.37 */
  53         364,    /* 0.38 */
  54         372,    /* 0.39 */
  55         380,    /* 0.40 */
  56         388,    /* 0.41 */
  57         397,    /* 0.42 */
  58         405,    /* 0.43 */
  59         412,    /* 0.44 */
  60         420,    /* 0.45 */
  61         428,    /* 0.46 */
  62         436,    /* 0.47 */
  63         443,    /* 0.48 */
  64         451,    /* 0.49 */
  65         458,    /* 0.50 */
  66         465,    /* 0.51 */
  67         472,    /* 0.52 */
  68         480,    /* 0.53 */
  69         487,    /* 0.54 */
  70         493,    /* 0.55 */
  71         500,    /* 0.56 */
  72         507,    /* 0.57 */
  73         514,    /* 0.58 */
  74         520,    /* 0.59 */
  75         527,    /* 0.60 */
  76         533,    /* 0.61 */
  77         540,    /* 0.62 */
  78         546,    /* 0.63 */
  79         552,    /* 0.64 */
  80         558,    /* 0.65 */
  81         564,    /* 0.66 */
  82         570,    /* 0.67 */
  83         576,    /* 0.68 */
  84         582,    /* 0.69 */
  85         587,    /* 0.70 */
  86         593,    /* 0.71 */
  87         598,    /* 0.72 */
  88         604,    /* 0.73 */
  89         609,    /* 0.74 */
  90         614,    /* 0.75 */
  91         620,    /* 0.76 */
  92         625,    /* 0.77 */
  93         630,    /* 0.78 */
  94         635,    /* 0.79 */
  95         640,    /* 0.80 */
  96         645,    /* 0.81 */
  97         649,    /* 0.82 */
  98         654,    /* 0.83 */
  99         659,    /* 0.84 */
 100         663,    /* 0.85 */
 101         668,    /* 0.86 */
 102         672,    /* 0.87 */
 103         676,    /* 0.88 */
 104         681,    /* 0.89 */
 105         685,    /* 0.90 */
 106         689,    /* 0.91 */
 107         693,    /* 0.92 */
 108         697,    /* 0.93 */
 109         701,    /* 0.94 */
 110         705,    /* 0.95 */
 111         709,    /* 0.96 */
 112         713,    /* 0.97 */
 113         717,    /* 0.98 */
 114         720,    /* 0.99 */
 115         724,    /* 1.00 */
 116         728,    /* 1.01 */
 117 };
 118
 119 static
 120 short cosinus[] = {
 121         1024,   /* 0.00 */
 122         1024,   /* 0.01 */
 123         1024,   /* 0.02 */
 124         1024,   /* 0.03 */
 125         1023,   /* 0.04 */
 126         1023,   /* 0.05 */
 127         1022,   /* 0.06 */
 128         1022,   /* 0.07 */
 129         1021,   /* 0.08 */
 130         1020,   /* 0.09 */
 131         1019,   /* 0.10 */
 132         1018,   /* 0.11 */
 133         1017,   /* 0.12 */
 134         1015,   /* 0.13 */
 135         1014,   /* 0.14 */
 136         1013,   /* 0.15 */
 137         1011,   /* 0.16 */
 138         1010,   /* 0.17 */
 139         1008,   /* 0.18 */
 140         1006,   /* 0.19 */
 141         1004,   /* 0.20 */
 142         1002,   /* 0.21 */
 143         1000,   /* 0.22 */
 144         998,    /* 0.23 */
 145         996,    /* 0.24 */
 146         993,    /* 0.25 */
 147         991,    /* 0.26 */
 148         989,    /* 0.27 */
 149         986,    /* 0.28 */
 150         983,    /* 0.29 */
 151         981,    /* 0.30 */
 152         978,    /* 0.31 */
 153         975,    /* 0.32 */
 154         972,    /* 0.33 */
 155         969,    /* 0.34 */
 156         967,    /* 0.35 */
 157         963,    /* 0.36 */
 158         960,    /* 0.37 */
 159         957,    /* 0.38 */
 160         954,    /* 0.39 */
 161         951,    /* 0.40 */
 162         947,    /* 0.41 */
 163         944,    /* 0.42 */
 164         941,    /* 0.43 */
 165         937,    /* 0.44 */
 166         934,    /* 0.45 */
 167         930,    /* 0.46 */
 168         927,    /* 0.47 */
 169         923,    /* 0.48 */
 170         920,    /* 0.49 */
 171         916,    /* 0.50 */
 172         912,    /* 0.51 */
 173         909,    /* 0.52 */
 174         905,    /* 0.53 */
 175         901,    /* 0.54 */
 176         897,    /* 0.55 */
 177         893,    /* 0.56 */
 178         890,    /* 0.57 */
 179         886,    /* 0.58 */
 180         882,    /* 0.59 */
 181         878,    /* 0.60 */
 182         874,    /* 0.61 */
 183         870,    /* 0.62 */
 184         866,    /* 0.63 */
 185         862,    /* 0.64 */
 186         859,    /* 0.65 */
 187         855,    /* 0.66 */
 188         851,    /* 0.67 */
 189         847,    /* 0.68 */
 190         843,    /* 0.69 */
 191         839,    /* 0.70 */
 192         835,    /* 0.71 */
 193         831,    /* 0.72 */
 194         827,    /* 0.73 */
 195         823,    /* 0.74 */
 196         819,    /* 0.75 */
 197         815,    /* 0.76 */
 198         811,    /* 0.77 */
 199         807,    /* 0.78 */
 200         804,    /* 0.79 */
 201         800,    /* 0.80 */
 202         796,    /* 0.81 */
 203         792,    /* 0.82 */
 204         788,    /* 0.83 */
 205         784,    /* 0.84 */
 206         780,    /* 0.85 */
 207         776,    /* 0.86 */
 208         773,    /* 0.87 */
 209         769,    /* 0.88 */
 210         765,    /* 0.89 */
 211         761,    /* 0.90 */
 212         757,    /* 0.91 */
 213         754,    /* 0.92 */
 214         750,    /* 0.93 */
 215         746,    /* 0.94 */
 216         742,    /* 0.95 */
 217         739,    /* 0.96 */
 218         735,    /* 0.97 */
 219         731,    /* 0.98 */
 220         728,    /* 0.99 */
 221         724,    /* 1.00 */
 222         720,    /* 1.01 */
 223 };
 224
 225 void
 226 icossin2(int x, int y, int *cosp, int *sinp)
 227 {
 228         int sinsign, cossign, tan, tan10, rem;
 229         short *stp, *ctp;
 230
 231         if(x == 0){
 232                 if(y >= 0)
 233                         *sinp = ICOSSCALE, *cosp = 0;
 234                 else
 235                         *sinp = -ICOSSCALE, *cosp = 0;
 236                 return;
 237         }
 238         sinsign = cossign = 1;
 239         if(x < 0){
 240                 cossign = -1;
 241                 x = -x;
 242         }
 243         if(y < 0){
 244                 sinsign = -1;
 245                 y = -y;
 246         }
 247         if(y > x){
 248                 tan = 1000*x/y;
 249                 tan10 = tan/10;
 250                 stp = &cosinus[tan10];
 251                 ctp = &sinus[tan10];
 252         }else{
 253                 tan = 1000*y/x;
 254                 tan10 = tan/10;
 255                 stp = &sinus[tan10];
 256                 ctp = &cosinus[tan10];
 257         }
 258         rem = tan-(tan10*10);
 259         *sinp = sinsign*(stp[0]+(stp[1]-stp[0])*rem/10);
 260         *cosp = cossign*(ctp[0]+(ctp[1]-ctp[0])*rem/10);
 261 }