How do you do a raycast in empty space?

I'm using Raycasting to point my gun where my cursor is in the 3D world. I can point at the terrain, crates, enemies but Raycasting doesn't work on the empty space. How would I be able to Raycast in the spaces that aren't colliders? Do I use some sort of skybox?

 

If the ray you're casting hits nothing, use some distance from the camera as the aim point -

eg

Code (csharp):

1. var aimDistance : float = 10.0;
2. var rch : RaycastHit;
3. var ray : Ray = Camera.main.ScreenPointToRay( Input.mousePosition );
4.  
5. if ( Physics.Raycast( ray, rch, aimDistance ) ) {
6.   aimpoint = rch.point;
7. } else {
8.   aimpoint = ray.origin + ray.direction * aimDistance;
9. }

 

This is works well for me.. thanks..

 

Try this:

RaycastHit hit;

if(hit.collider == null)
return;

Check if the RaycastHit's collider is null.