Graphic Raycaster component

The Graphic Raycaster allows you to check to see whether objects on the Canvas have been hit by a user input using the EventSystem. As discussed when looking at the World Space Canvas Render Mode, when a user touches the screen, a ray is cast forward from the point on the screen at which the player touches. The Graphic Raycaster checks these rays and sees if they hit something on the Canvas.

You can adjust the following properties on the Graphic Raycaster component:

• Ignore Reversed Graphics: If a UI element is facing away from the player, having this selected will stop the hit from registering. If it is not selected, hits will register on back-facing UI objects.
• Blocking Objects: This setting specifies which types of items in front of it will block it from being hit. So, if you select Two D, any Two D object in front of the items on this Canvas will stop the items from being interacted with. However, 3D objects will not stop the interaction. The possible options are shown here:
  
  

• Blocking Mask: Selecting items on this property works similar to the Blocking Objects property. This allows you to select items based on their Rendering Layer, so you can get a little more specific. The possible options are shown as follows:
  
  

We will discuss Raycasting and the EventSystem more thoroughly in Chapter 4, The Event System and Programming for UI.