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(const rect_t *object,
  69                         const rect_t *obstacle,
  70                         int *sides)
  71 {
  72     assert(object);
  73     assert(obstacle);
  74     assert(sides);
  75
  76     rect_t int_area = rects_overlap_area(*object, *obstacle);
  77
  78     if (int_area.w * int_area.h > 0.0f) {
  79         for (int side = 0; side < RECT_SIDE_N; ++side) {
  80             line_t object_side = rect_side(*object, side);
  81             line_t int_side = rect_side(int_area, side);
  82
  83             if (line_length(int_side) > 10.0f) {
  84                 sides[side] = sides[side] ||
  85                     (fabs(object_side.p1.x - object_side.p2.x) < 1e-6
  86                      && fabs(object_side.p1.x - int_side.p1.x) < 1e-6
  87                      && fabs(object_side.p1.x - int_side.p2.x) < 1e-6)
  88                     || (fabs(object_side.p1.y - object_side.p2.y) < 1e-6
  89                         && fabs(object_side.p1.y - int_side.p1.y) < 1e-6
  90                         && fabs(object_side.p1.y - int_side.p2.y) < 1e-6);
  91             }
  92         }
  93     }
  94 }
  95
  96 line_t rect_side(rect_t rect, rect_side_t side)
  97 {
  98     const float x1 = rect.x;
  99     const float y1 = rect.y;
 100     const float x2 = rect.x + rect.w;
 101     const float y2 = rect.y + rect.h;
 102
 103     line_t result;
 104
 105     switch (side) {
 106     case RECT_SIDE_LEFT:
 107         result.p1.x = x1;
 108         result.p1.y = y1;
 109         result.p2.x = x1;
 110         result.p2.y = y2;
 111         break;
 112     case RECT_SIDE_RIGHT:
 113         result.p1.x = x2;
 114         result.p1.y = y1;
 115         result.p2.x = x2;
 116         result.p2.y = y2;
 117         break;
 118     case RECT_SIDE_TOP:
 119         result.p1.x = x1;
 120         result.p1.y = y1;
 121         result.p2.x = x2;
 122         result.p2.y = y1;
 123         break;
 124     case RECT_SIDE_BOTTOM:
 125         result.p1.x = x1;
 126         result.p1.y = y2;
 127         result.p2.x = x2;
 128         result.p2.y = y2;
 129         break;
 130     default: {}
 131     }
 132
 133     return result;
 134 }
 135
 136 rect_t rect_from_point(point_t p, float w, float h)
 137 {
 138     rect_t result = {
 139         .x = p.x,
 140         .y = p.y,
 141         .w = w,
 142         .h = h
 143     };
 144
 145     return result;
 146 }
 147
 148 int rect_contains_point(rect_t rect, point_t p)
 149 {
 150     return rect.x <= p.x && p.x <= rect.x + rect.w
 151         && rect.y <= p.y && p.y <= rect.y + rect.h;
 152 }
 153
 154 SDL_Rect rect_for_sdl(rect_t rect)
 155 {
 156     const SDL_Rect result = {
 157         .x = (int) roundf(rect.x),
 158         .y = (int) roundf(rect.y),
 159         .w = (int) roundf(rect.w),
 160         .h = (int) roundf(rect.h)
 161     };
 162
 163     return result;
 164 }