src/math/rect.c

   1 #include <SDL2/SDL.h>
   2 #include <assert.h>
   3 #include <math.h>
   4 #include <string.h>
   5
   6 #include "rect.h"
   7
   8 rect_t rect(float x, float y, float w, float h)
   9 {
  10     const rect_t result = {
  11         .x = x,
  12         .y = y,
  13         .w = w,
  14         .h = h
  15     };
  16
  17     return result;
  18 }
  19
  20 rect_t rect_from_vecs(point_t position, vec_t size)
  21 {
  22     return rect(position.x, position.y, size.x, size.y);
  23 }
  24
  25 rect_t rect_from_sdl(const SDL_Rect *rect)
  26 {
  27     const rect_t result = {
  28         .x = (float) rect->x,
  29         .y = (float) rect->y,
  30         .w = (float) rect->w,
  31         .h = (float) rect->h
  32     };
  33
  34     return result;
  35 }
  36
  37 rect_t rects_overlap_area(rect_t rect1, rect_t rect2)
  38 {
  39     float x1 = fmaxf(rect1.x, rect2.x);
  40     float y1 = fmaxf(rect1.y, rect2.y);
  41     float x2 = fminf(rect1.x + rect1.w, rect2.x + rect2.w);
  42     float y2 = fminf(rect1.y + rect1.h, rect2.y + rect2.h);
  43
  44     rect_t result = {
  45         .x = x1,
  46         .y = y1,
  47         .w = fmaxf(0.0f, x2 - x1),
  48         .h = fmaxf(0.0f, y2 - y1)
  49     };
  50     return result;
  51 }
  52
  53 int rects_overlap(rect_t rect1, rect_t rect2)
  54 {
  55     return rect1.x + rect1.w >= rect2.x
  56         && rect2.x + rect2.w >= rect1.x
  57         && rect2.y + rect2.h >= rect1.y
  58         && rect1.y + rect1.h >= rect2.y;
  59 }
  60
  61 float line_length(line_t line)
  62 {
  63     float dx = line.p1.x - line.p2.x;
  64     float dy = line.p1.y - line.p2.y;
  65     return sqrtf(dx * dx + dy * dy);
  66 }
  67
  68 void rect_object_impact(rect_t object, rect_t obstacle, int *sides)
  69 {
  70     assert(sides);
  71
  72     rect_t int_area = rects_overlap_area(object, obstacle);
  73
  74     if (int_area.w * int_area.h > 0.0f) {
  75         for (int side = 0; side < RECT_SIDE_N; ++side) {
  76             line_t object_side = rect_side(object, side);
  77             line_t int_side = rect_side(int_area, side);
  78
  79             if (line_length(int_side) > 10.0f) {
  80                 sides[side] = sides[side] ||
  81                     (fabs(object_side.p1.x - object_side.p2.x) < 1e-6
  82                      && fabs(object_side.p1.x - int_side.p1.x) < 1e-6
  83                      && fabs(object_side.p1.x - int_side.p2.x) < 1e-6)
  84                     || (fabs(object_side.p1.y - object_side.p2.y) < 1e-6
  85                         && fabs(object_side.p1.y - int_side.p1.y) < 1e-6
  86                         && fabs(object_side.p1.y - int_side.p2.y) < 1e-6);
  87             }
  88         }
  89     }
  90 }
  91
  92 line_t rect_side(rect_t rect, rect_side_t side)
  93 {
  94     const float x1 = rect.x;
  95     const float y1 = rect.y;
  96     const float x2 = rect.x + rect.w;
  97     const float y2 = rect.y + rect.h;
  98
  99     line_t result;
 100
 101     switch (side) {
 102     case RECT_SIDE_LEFT:
 103         result.p1.x = x1;
 104         result.p1.y = y1;
 105         result.p2.x = x1;
 106         result.p2.y = y2;
 107         break;
 108     case RECT_SIDE_RIGHT:
 109         result.p1.x = x2;
 110         result.p1.y = y1;
 111         result.p2.x = x2;
 112         result.p2.y = y2;
 113         break;
 114     case RECT_SIDE_TOP:
 115         result.p1.x = x1;
 116         result.p1.y = y1;
 117         result.p2.x = x2;
 118         result.p2.y = y1;
 119         break;
 120     case RECT_SIDE_BOTTOM:
 121         result.p1.x = x1;
 122         result.p1.y = y2;
 123         result.p2.x = x2;
 124         result.p2.y = y2;
 125         break;
 126     default: {}
 127     }
 128
 129     return result;
 130 }
 131
 132 rect_t rect_from_point(point_t p, float w, float h)
 133 {
 134     rect_t result = {
 135         .x = p.x,
 136         .y = p.y,
 137         .w = w,
 138         .h = h
 139     };
 140
 141     return result;
 142 }
 143
 144 int rect_contains_point(rect_t rect, point_t p)
 145 {
 146     return rect.x <= p.x && p.x <= rect.x + rect.w
 147         && rect.y <= p.y && p.y <= rect.y + rect.h;
 148 }
 149
 150 SDL_Rect rect_for_sdl(rect_t rect)
 151 {
 152     const SDL_Rect result = {
 153         .x = (int) roundf(rect.x),
 154         .y = (int) roundf(rect.y),
 155         .w = (int) roundf(rect.w),
 156         .h = (int) roundf(rect.h)
 157     };
 158
 159     return result;
 160 }