Add line-AABB collision check function

scenes/engine/AABB.c

@@ -49,3 +49,45 @@ bool point_in_AABB(Vector2 point, Rectangle box)
         && point.y < box.y + box.height
     );
 }
+
+bool line_in_AABB(Vector2 p1, Vector2 p2, Rectangle box)
+{
+    float A = p2.y - p1.y;
+    float B = p1.x - p2.x;
+    float C = (p2.x * p1.y) - (p1.x * p2.y);
+
+    Vector2 corners[3] = 
+    {
+        {box.x + box.width - 1, box.y},
+        {box.x + box.width - 1, box.y + box.height - 1},
+        {box.x, box.y + box.height - 1},
+    };
+
+    float F = (A * box.x + B * box.y + C);
+    uint8_t last_mode = 0;
+    if (fabs(F) < 1e-3)
+    {
+        last_mode = 0;
+    }
+    else
+    {
+        last_mode = (F > 0) ? 1 : 2;
+    }
+    for (uint8_t i = 0; i < 3; ++i)
+    {
+
+        F = (A * corners[i].x + B * corners[i].y + C);
+        uint8_t mode = 0;
+        if (fabs(F) < 1e-3)
+        {
+            mode = 0;
+        }
+        else
+        {
+            mode = (F > 0) ? 1 : 2;
+        }
+        if (mode != last_mode) return true;
+        last_mode = mode;
+    }
+    return false;
+}

scenes/engine/AABB.h

@@ -6,4 +6,5 @@
 uint8_t find_1D_overlap(Vector2 l1, Vector2 l2, float* overlap);
 uint8_t find_AABB_overlap(const Vector2 tl1, const Vector2 sz1, const Vector2 tl2, const Vector2 sz2, Vector2* overlap);
 bool point_in_AABB(Vector2 point, Rectangle box);
+bool line_in_AABB(Vector2 p1, Vector2 p2, Rectangle box);
 #endif // __AABB_H

tests/test_AABB.c

@@ -6,6 +6,44 @@
 #include <setjmp.h>
 #include <cmocka.h>
 
+static void test_line_AABB(void **state)
+{
+    (void) state;
+
+    Vector2 p1 = {0, 0};
+    Vector2 p2 = {20, 20};
+
+    Rectangle box = {5, 0, 10, 20};
+    assert_true(line_in_AABB(p1, p2, box));
+
+    p1.y = 20;
+    assert_false(line_in_AABB(p1, p2, box));
+
+    p1.y = 19;
+    p2 = (Vector2){19, 19};
+    assert_true(line_in_AABB(p1, p2, box));
+
+    p1.y = 0;
+    p2.y = 0;
+    assert_true(line_in_AABB(p1, p2, box));
+
+    p1 = (Vector2){5, 0};
+    p2 = (Vector2){5, 10};
+    assert_true(line_in_AABB(p1, p2, box));
+
+    p1 = (Vector2){14, 0};
+    p2 = (Vector2){14, 10};
+    assert_true(line_in_AABB(p1, p2, box));
+
+    p1 = (Vector2){15, 0};
+    p2 = (Vector2){15, 10};
+    assert_false(line_in_AABB(p1, p2, box));
+
+    p1 = (Vector2){0, 30};
+    p2 = (Vector2){6, 35};
+    assert_false(line_in_AABB(p1, p2, box));
+}
+
 static void test_point_AABB(void **state)
 {
     (void) state;
@@ -86,6 +124,7 @@ int main(void)
         cmocka_unit_test(test_1D_overlap),
         cmocka_unit_test(test_AABB_overlap),
         cmocka_unit_test(test_point_AABB),
+        cmocka_unit_test(test_line_AABB),
     };
 
     return cmocka_run_group_tests(tests, NULL, NULL);