Initial commit

1 files changed, 130 insertions, 0 deletions

diff --git a/collisions.c b/collisions.c
new file mode 100644
index 0000000..e9f0c13
--- /dev/null
+++ b/collisions.c
@@ -0,0 +1,130 @@
+#include "game.h"
+
+struct FRect
+{
+  float x, y, w, h;
+};
+
+static inline bool colliding2D(const struct FRect *a, const struct FRect *b)
+{
+  return ((a->x + a->w > b->x && a->x < b->x + b->w)
+	  && (a->y + a->h > b->y && a->y < b->y + b->h));
+}
+
+bool frect_intersect(const struct FRect *a, const struct FRect *b, struct FRect *res)
+{
+  res->x = fmaxf(a->x, b->x);
+  res->w = fminf(a->x + a->w, b->x + b->w) - fmaxf(a->x, b->x);
+  res->y = fmaxf(a->y, b->y);
+  res->h = fminf(a->y + a->h, b->y + b->h) - fmaxf(a->y, b->y);
+
+  return colliding2D(a, b);
+}
+
+bool colliding_vertically(const struct Entity *a, const struct Entity *b, const struct FRect *res)
+{
+  //return a->y + a->h < b->y + b->h / 2.0f || b->y + b->h < a->y + a->h / 2.0f;
+  return res->w > res->h;
+}
+
+void collide_with_fixed(struct Entity *e, struct Entity *fixed, const struct FRect *res)
+{
+  // Check if either of the boxes
+  if( colliding_vertically(e, fixed, res) )
+    {
+      e->y += (e->y < fixed->y) ? -res->h : res->h;
+      e->dy = 0.0f;
+    }
+  else
+    {
+      e->x += (e->x < fixed->x) ? -res->w : res->w;
+      e->dx = 0.0f;
+    }
+}
+
+void collide(struct Entity *a, struct Entity *b, const struct FRect *res)
+{
+  float a_disp, b_disp;
+
+  float vx_sum, vy_sum;
+  vx_sum = fabsf(a->dx) + fabsf(b->dx);
+  vy_sum = fabsf(a->dy) + fabsf(b->dy);
+
+  // Check if either of the boxes
+  if( colliding_vertically(a, b, res) )
+    {
+      a_disp = vy_sum == 0.0f ? res->h / 2.0f : res->h * (fabsf(a->dy) / vy_sum);
+      b_disp = vy_sum == 0.0f ? res->h / 2.0f : res->h * (fabsf(b->dy) / vy_sum);
+      //a_disp = res->h / 2.0f;
+      //b_disp = res->h / 2.0f;
+
+      a->y += (a->y < b->y) ? -a_disp : a_disp;
+      b->y -= (a->y < b->y) ? -b_disp : b_disp;
+
+      a->dy = 0.0f;
+      b->dy = 0.0f;
+    }
+  else
+    {
+      a_disp = vx_sum == 0.0f ? res->w / 2.0f : res->w * (fabsf(a->dx) / vx_sum);
+      b_disp = vx_sum == 0.0f ? res->w / 2.0f : res->w * (fabsf(b->dx) / vx_sum);
+      //a_disp = res->w / 2.0f;
+      //b_disp = res->w / 2.0f;
+
+      a->x += (a->x < b->x) ? -a_disp : a_disp;
+      b->x -= (a->x < b->x) ? -b_disp : b_disp;
+
+      a->dx = 0.0f;
+      b->dx = 0.0f;
+    }
+}
+
+void check_collisions(void)
+{
+  int i, j;
+  struct Entity *a, *b;
+
+  for(i = 0; i < game->num_entities; i ++)
+    {
+      a = game->entities[i];
+
+      if(!a)
+	continue;
+
+      for(j = i + 1; j < game->num_entities; j ++)
+	{
+	  b = game->entities[j];
+
+	  if(!b)
+	    continue;
+
+	  struct FRect res;
+	  struct FRect r1 = {a->x, a->y, a->w, a->h};
+	  struct FRect r2 = {b->x, b->y, b->w, b->h};
+
+	  if( frect_intersect(&r1, &r2, &res) )
+	    {
+	      if(a->collidable && b->collidable)
+		{
+		  if(!a->fixed && !b->fixed)
+		    {
+		      collide(a, b, &res);
+		    }
+		  else if(a->fixed && !b->fixed)
+		    {
+		      collide_with_fixed(b, a, &res);
+		    }
+		  else if(!a->fixed && b->fixed)
+		    {
+		      collide_with_fixed(a, b, &res);
+		    }
+		}
+
+	      if(a->on_collision)
+		a->on_collision(a, b);
+	      if(b->on_collision)
+		b->on_collision(b, a);
+	    }
+	}
+    }
+}