Weapons - Pro Unity Game Development with C# - page 197

Listing 6-6. Detecting Enemy Hits
062 //Calculate hit
063
064 //Get ray from screen center target
065 Ray R = Camera.main.ScreenPointToRay(new Vector3(Screen.width/2,
Screen.height/2,0));
066
067 //Test for ray collision
068 RaycastHit hit;
069
070 if(Physics.Raycast(R.origin, R.direction, out hit, Range))
071 {
072 //Target hit - check if target is enemy
073 if(hit.collider.gameObject.CompareTag("enemy"))
074 {
075 //Play collection sound, if audio source is available
076 if(SFX){SFX.PlayOneShot(WeaponAudio, 1.0f);}
077
078 //Send damage message (deal damage to enemy)
079 hit.collider.gameObject.SendMessage("Damage",Damage,
SendMessageOptions.DontRequireReceiver);
080 }
081 }
082
Collision detection and damage dealing begins by constructing a ray . A ray is a mathematical
structure representing an imaginary straight line, projected from the screen into the scene space
ahead. In our case, the ray will act as an imaginary beam cast outward from the tip of our weapon
(assumed to be screen-center). Line 65 uses the Unity camera function ScreenPointToRay to
construct a ray that begins from the screen center and is projected forward, away from the camera
and inward into the scene.
Note More information on ScreenPointToRay can be found in the online Unity documentation at
http://docs.unity3d.com/Documentation/ScriptReference/Camera.ScreenPointToRay.html .
After a ray has been constructed and cast into the scene, the Physics.Raycast function is used
to access the first collidable GameObject intersecting the ray. This object is the nearest collidable
object to us .
Note More information on Physics.Raycast can be found in the online Unity documentation at
http://docs.unity3d.com/Documentation/ScriptReference/Physics.Raycast.html .