c# - Unity3D Physics2D.OverlapAreaNonAlloc strange (bug?) behaviours with layers -

i have encountered strange bug physics2d.overlapareanonalloc , created test project confirm it.

scene : 2 cube on top of each other, rigidbody2d , box collider, bottom 1 kinematic. top 1 "player".

i wanted use physics2d.overlapareanonalloc enemy detection used code looks this, attached player :

using unityengine; using system.collections;  public class test : monobehaviour {      vector2 pointa;     vector2 pointb;     collider2d[] enemies = new collider2d[2];      void update () {          //enemy detection         pointa = (vector2)gameobject.transform.position - new vector2(0.1f, 0f);         pointb = (vector2)gameobject.transform.position + new vector2(0.1f, 0.1f);          if (physics2d.overlapareanonalloc(pointa, pointb, enemies, 9) > 0)         {             debug.log("first enemy :" + enemies[0].name);         }     } } 

9 layer number of enemies layer. there no enemies in scene previous code should never display in console. sadly...

when run code, here happens : - if "player" layer default, somehow detected physics2d.overlapareanonalloc - if "player" layer layer, not detected.

i don't understand behaviour, "default" supposed "super" layer contains layers ?

use layermask.getmask() in call physics2d.overlapareanonalloc().

// "enemy" represents layer assigned enemies physics2d.overlapareanonalloc(pointa, pointb, enemies, layermask.getmask("enemy"))