Handle wrapping in physics_separation()

physics.c

@@ -4,6 +4,7 @@
 #include "renderer.h"
 
 #include <assert.h>
+#include <math.h>
 #include <string.h>
 
 typedef struct {
@@ -97,16 +98,38 @@ void physics_escape(unsigned entity)
 	escape_entity = entity;
 }
 
+static void pos_views(vec2_t a, vec2_t b, vec2_t out[4])
+{
+	const float dx = 2 * aspect;
+	const float dy = 2;
+	out[0] = b;
+	out[1] = (vec2_t) { b.x + copysign(dx, a.x), b.y };
+	out[2] = (vec2_t) { b.x, b.y + copysign(dy, a.y) };
+	out[3] = (vec2_t) { b.x + copysign(dx, a.x), b.y + copysign(dy, a.y) };
+}
+
 physics_sep_t physics_separation(unsigned a, unsigned b)
 {
 	const physics_t *pa = physics_get(a);
 	const physics_t *pb = physics_get(b);
 
-	const vec2_t disp = vec2_sub(pb->pos, pa->pos);
+	vec2_t pos[4];
-	const vec2_t norm = vec2_norm(disp);
+	pos_views(pa->pos, pb->pos, pos);
 
+	float min_dist = INFINITY;
+	vec2_t min_disp;
+	for (unsigned i = 0; i < 4; ++i) {
+		const vec2_t disp = vec2_sub(pos[i], pa->pos);
+		const float dist = vec2_len(disp);
+		if (dist < min_dist) {
+			min_disp = disp;
+			min_dist = dist;
+		}
+	}
+
+	const vec2_t norm = vec2_norm(min_disp);
 	return (physics_sep_t) {
-		.dist = vec2_len(disp),
+		.dist = min_dist,
 		.norm = norm,
 		.va = vec2_dot(pa->vel, norm),
 		.vb = vec2_dot(pb->vel, norm),