src/util/numeric.cpp

   1 /*
   2 Minetest
   3 Copyright (C) 2010-2013 celeron55, Perttu Ahola <celeron55@gmail.com>
   4
   5 This program is free software; you can redistribute it and/or modify
   6 it under the terms of the GNU Lesser General Public License as published by
   7 the Free Software Foundation; either version 2.1 of the License, or
   8 (at your option) any later version.
   9
  10 This program is distributed in the hope that it will be useful,
  11 but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 GNU Lesser General Public License for more details.
  14
  15 You should have received a copy of the GNU Lesser General Public License along
  16 with this program; if not, write to the Free Software Foundation, Inc.,
  17 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18 */
  19
  20 #include "numeric.h"
  21 #include "mathconstants.h"
  22
  23 #include "../log.h"
  24 #include "../constants.h" // BS, MAP_BLOCKSIZE
  25 #include <iostream>
  26
  27 // Calculate the borders of a "d-radius" cube
  28 void getFacePositions(std::list<v3s16> &list, u16 d)
  29 {
  30         if(d == 0)
  31         {
  32                 list.push_back(v3s16(0,0,0));
  33                 return;
  34         }
  35         if(d == 1)
  36         {
  37                 /*
  38                         This is an optimized sequence of coordinates.
  39                 */
  40                 list.push_back(v3s16( 0, 1, 0)); // top
  41                 list.push_back(v3s16( 0, 0, 1)); // back
  42                 list.push_back(v3s16(-1, 0, 0)); // left
  43                 list.push_back(v3s16( 1, 0, 0)); // right
  44                 list.push_back(v3s16( 0, 0,-1)); // front
  45                 list.push_back(v3s16( 0,-1, 0)); // bottom
  46                 // 6
  47                 list.push_back(v3s16(-1, 0, 1)); // back left
  48                 list.push_back(v3s16( 1, 0, 1)); // back right
  49                 list.push_back(v3s16(-1, 0,-1)); // front left
  50                 list.push_back(v3s16( 1, 0,-1)); // front right
  51                 list.push_back(v3s16(-1,-1, 0)); // bottom left
  52                 list.push_back(v3s16( 1,-1, 0)); // bottom right
  53                 list.push_back(v3s16( 0,-1, 1)); // bottom back
  54                 list.push_back(v3s16( 0,-1,-1)); // bottom front
  55                 list.push_back(v3s16(-1, 1, 0)); // top left
  56                 list.push_back(v3s16( 1, 1, 0)); // top right
  57                 list.push_back(v3s16( 0, 1, 1)); // top back
  58                 list.push_back(v3s16( 0, 1,-1)); // top front
  59                 // 18
  60                 list.push_back(v3s16(-1, 1, 1)); // top back-left
  61                 list.push_back(v3s16( 1, 1, 1)); // top back-right
  62                 list.push_back(v3s16(-1, 1,-1)); // top front-left
  63                 list.push_back(v3s16( 1, 1,-1)); // top front-right
  64                 list.push_back(v3s16(-1,-1, 1)); // bottom back-left
  65                 list.push_back(v3s16( 1,-1, 1)); // bottom back-right
  66                 list.push_back(v3s16(-1,-1,-1)); // bottom front-left
  67                 list.push_back(v3s16( 1,-1,-1)); // bottom front-right
  68                 // 26
  69                 return;
  70         }
  71
  72         // Take blocks in all sides, starting from y=0 and going +-y
  73         for(s16 y=0; y<=d-1; y++)
  74         {
  75                 // Left and right side, including borders
  76                 for(s16 z=-d; z<=d; z++)
  77                 {
  78                         list.push_back(v3s16(d,y,z));
  79                         list.push_back(v3s16(-d,y,z));
  80                         if(y != 0)
  81                         {
  82                                 list.push_back(v3s16(d,-y,z));
  83                                 list.push_back(v3s16(-d,-y,z));
  84                         }
  85                 }
  86                 // Back and front side, excluding borders
  87                 for(s16 x=-d+1; x<=d-1; x++)
  88                 {
  89                         list.push_back(v3s16(x,y,d));
  90                         list.push_back(v3s16(x,y,-d));
  91                         if(y != 0)
  92                         {
  93                                 list.push_back(v3s16(x,-y,d));
  94                                 list.push_back(v3s16(x,-y,-d));
  95                         }
  96                 }
  97         }
  98
  99         // Take the bottom and top face with borders
 100         // -d<x<d, y=+-d, -d<z<d
 101         for(s16 x=-d; x<=d; x++)
 102         for(s16 z=-d; z<=d; z++)
 103         {
 104                 list.push_back(v3s16(x,-d,z));
 105                 list.push_back(v3s16(x,d,z));
 106         }
 107 }
 108
 109 /*
 110     myrand
 111 */
 112
 113 static unsigned long next = 1;
 114
 115 /* RAND_MAX assumed to be 32767 */
 116 int myrand(void)
 117 {
 118    next = next * 1103515245 + 12345;
 119    return((unsigned)(next/65536) % 32768);
 120 }
 121
 122 void mysrand(unsigned seed)
 123 {
 124    next = seed;
 125 }
 126
 127 int myrand_range(int min, int max)
 128 {
 129         if(max-min > MYRAND_MAX)
 130         {
 131                 errorstream<<"WARNING: myrand_range: max-min > MYRAND_MAX"<<std::endl;
 132         max = min + MYRAND_MAX;
 133         }
 134         if(min > max)
 135         {
 136                 errorstream<<"WARNING: myrand_range: min > max"<<std::endl;
 137                 return max;
 138         }
 139         return (myrand()%(max-min+1))+min;
 140 }
 141
 142 /*
 143         blockpos: position of block in block coordinates
 144         camera_pos: position of camera in nodes
 145         camera_dir: an unit vector pointing to camera direction
 146         range: viewing range
 147 */
 148 bool isBlockInSight(v3s16 blockpos_b, v3f camera_pos, v3f camera_dir,
 149                 f32 camera_fov, f32 range, f32 *distance_ptr)
 150 {
 151         v3s16 blockpos_nodes = blockpos_b * MAP_BLOCKSIZE;
 152
 153         // Block center position
 154         v3f blockpos(
 155                         ((float)blockpos_nodes.X + MAP_BLOCKSIZE/2) * BS,
 156                         ((float)blockpos_nodes.Y + MAP_BLOCKSIZE/2) * BS,
 157                         ((float)blockpos_nodes.Z + MAP_BLOCKSIZE/2) * BS
 158         );
 159
 160         // Block position relative to camera
 161         v3f blockpos_relative = blockpos - camera_pos;
 162
 163         // Total distance
 164         f32 d = blockpos_relative.getLength();
 165
 166         if(distance_ptr)
 167                 *distance_ptr = d;
 168
 169         // If block is far away, it's not in sight
 170         if(d > range)
 171                 return false;
 172
 173         // Maximum radius of a block.  The magic number is
 174         // sqrt(3.0) / 2.0 in literal form.
 175         f32 block_max_radius = 0.866025403784 * MAP_BLOCKSIZE * BS;
 176
 177         // If block is (nearly) touching the camera, don't
 178         // bother validating further (that is, render it anyway)
 179         if(d < block_max_radius)
 180                 return true;
 181
 182         // Adjust camera position, for purposes of computing the angle,
 183         // such that a block that has any portion visible with the
 184         // current camera position will have the center visible at the
 185         // adjusted postion
 186         f32 adjdist = block_max_radius / cos((M_PI - camera_fov) / 2);
 187
 188         // Block position relative to adjusted camera
 189         v3f blockpos_adj = blockpos - (camera_pos - camera_dir * adjdist);
 190
 191         // Distance in camera direction (+=front, -=back)
 192         f32 dforward = blockpos_adj.dotProduct(camera_dir);
 193
 194         // Cosine of the angle between the camera direction
 195         // and the block direction (camera_dir is an unit vector)
 196         f32 cosangle = dforward / blockpos_adj.getLength();
 197
 198         // If block is not in the field of view, skip it
 199         if(cosangle < cos(camera_fov / 2))
 200                 return false;
 201
 202         return true;
 203 }
 204