mirror of https://github.com/dirtbags/tanks.git
160 lines
3.2 KiB
C
160 lines
3.2 KiB
C
#include <stdlib.h>
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#include "brad.h"
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#ifndef max
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#define max(a,b) (((a) > (b)) ? (a) : (b))
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#define min(a,b) (((a) < (b)) ? (a) : (b))
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#endif
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/* Approximate vector length
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*
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* http://www.flipcode.com/archives/Fast_Approximate_Distance_Functions.shtml
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*
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* (1007/1024) * 256 == 251.75
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* (441/1024) * 256 == 110.25
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*/
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bs_t
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bs_approx_dist(bs_t dx, bs_t dy)
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{
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bs_t x = abs(dx);
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bs_t y = abs(dy);
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return (252 * max(x, y)) + (110 * min(x, y));
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}
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static bs_t bs_cos_table[] = {
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256, 256, 256, 255, 255, 254, 253, 252,
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251, 250, 248, 247, 245, 243, 241, 239,
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237, 234, 231, 229, 226, 223, 220, 216,
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213, 209, 206, 202, 198, 194, 190, 185,
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181, 177, 172, 167, 162, 157, 152, 147,
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142, 137, 132, 126, 121, 115, 109, 104,
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98, 92, 86, 80, 74, 68, 62, 56,
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50, 44, 38, 31, 25, 19, 13, 6,
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0
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};
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bs_t
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bs_cos(brad_t angle)
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{
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brad_t cos;
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bs_t a;
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a = abs(angle) % 128;
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if (a > 64) {
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a = 128 - a;
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}
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cos = bs_cos_table[a];
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a = abs(angle) % 256;
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if ((a > 64) && (a < 192)) {
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cos = -cos;
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}
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return cos;
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}
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bs_t
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bs_sin(brad_t angle)
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{
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return bs_cos(64 - angle);
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}
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bs_t
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bs_tan(brad_t angle)
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{
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return bs_sin(angle) / bs_cos(angle);
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}
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static brad_t bs_asin_table[] = {
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0, 0, 1, 1, 1, 2, 2, 2,
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3, 3, 3, 4, 4, 4, 4, 5,
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5, 5, 6, 6, 6, 7, 7, 7,
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8, 8, 8, 9, 9, 9, 10, 10,
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10, 11, 11, 11, 11, 12, 12, 12,
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13, 13, 13, 14, 14, 14, 15, 15,
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15, 16, 16, 16, 17, 17, 17, 18,
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18, 18, 19, 19, 19, 20, 20, 20,
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21, 21, 21, 22, 22, 22, 23, 23,
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23, 24, 24, 24, 25, 25, 25, 26,
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26, 26, 27, 27, 27, 28, 28, 28,
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29, 29, 29, 30, 30, 30, 31, 31,
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31, 32, 32, 32, 33, 33, 33, 34,
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34, 34, 35, 35, 35, 36, 36, 37,
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37, 37, 38, 38, 38, 39, 39, 39,
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40, 40, 40, 41, 41, 42, 42, 42,
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43, 43, 43, 44, 44, 45, 45, 45,
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46, 46, 46, 47, 47, 48, 48, 48,
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49, 49, 49, 50, 50, 51, 51, 51,
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52, 52, 53, 53, 53, 54, 54, 55,
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55, 55, 56, 56, 57, 57, 57, 58,
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58, 59, 59, 60, 60, 60, 61, 61,
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62, 62, 63, 63, 64, 64, 64, 65,
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65, 66, 66, 67, 67, 68, 68, 69,
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69, 70, 70, 71, 71, 72, 72, 73,
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73, 74, 74, 75, 75, 76, 76, 77,
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77, 78, 78, 79, 80, 80, 81, 81,
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82, 82, 83, 84, 84, 85, 86, 86,
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87, 87, 88, 89, 90, 90, 91, 92,
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92, 93, 94, 95, 96, 96, 97, 98,
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99, 100, 101, 102, 103, 104, 105, 106,
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108, 109, 110, 112, 114, 116, 118, 121,
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128
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};
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brad_t
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bs_asin(bs_t n)
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{
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bs_t a = abs(n);
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brad_t ret;
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if (a > 256) {
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return 0;
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}
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ret = bs_asin_table[a];
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if (n < 0) {
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ret = -ret;
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}
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return ret;
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}
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brad_t
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bs_acos(bs_t n)
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{
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return 128 - bs_asin(n);
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}
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brad_t
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bs_atan2(bs_t y, bs_t x)
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{
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bs_t r = bs_approx_dist(x, y);
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brad_t t;
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t = bs_acos(x / r);
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if (y < 0) {
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t = 256 - t;
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}
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return t;
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}
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#include <math.h>
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#include <stdio.h>
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#define PI 3.14159265358979323846
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int
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main()
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{
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int i, j;
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float f;
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int t;
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for (i = 0; i < 257; i += 1) {
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for (j = 0; j < 257; j += 1) {
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f = sqrt(i*i + j*j);
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t = bs_approx_dist(i, j);
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printf("%d %d %d\n", i, (int)round(f*256)/256, t/256);
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}
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}
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return 0;
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}
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