Raycast across angle?

Edited :

Ok, I have written a new answer for the new information provided.

This script works by calculating a point that is at an angle to the object forward. This angle is then changed by the angle divided by the number of times (segments).

press play, and left click mouse button to briefly see the lines of the raycast (you can spam the LMB for testing just to see the lines where the Linecast is checking. While playing, change the angle and the segments, just make sure that segments is always less than theAngle. And I have made these variables integers, though floats could be used, this is probably accurate enough for what you need.

 #pragma strict
 
 public var distance : float = 5.0f;
 public var theAngle : int = 45;
 public var segments : int = 10;
 
 function Update() 
 {
     if ( Input.GetMouseButtonDown(0) )
     {
         RaycastSweep();
     }
 }
 
 function RaycastSweep() 
 {
     var startPos : Vector3 = transform.position; // umm, start position !
     var targetPos : Vector3 = Vector3.zero; // variable for calculated end position
     
     var startAngle : int = parseInt( -theAngle * 0.5 ); // half the angle to the Left of the forward
     var finishAngle : int = parseInt( theAngle * 0.5 ); // half the angle to the Right of the forward
     
     // the gap between each ray (increment)
     var inc : int = parseInt( theAngle / segments );
     
     var hit : RaycastHit;
     
     // step through and find each target point
     for ( var i : int = startAngle; i < finishAngle; i += inc ) // Angle from forward
     {
         targetPos = (Quaternion.Euler( 0, i, 0 ) * transform.forward ).normalized * distance;    
         
         // linecast between points
         if ( Physics.Linecast( startPos, targetPos, hit ) )
         {
             Debug.Log( "Hit " + hit.collider.gameObject.name );
         }    
         
         // to show ray just for testing
         Debug.DrawLine( startPos, targetPos, Color.green );    
     }        
 }

Let me know =]

Original answer

I found this question very interesting so decided to have a go =]

A list of 'nodes' is generated based on the number of segments in the arc and the range of a circle. Set the circle range with curveAmount (eg 90 = 90', 360' = full circle). Also set the radius and the number of segments (this can all be done in realtime within the script.

This is just an example with some debug lines to demonstrate. Attach script to empty gameObject, hit play and then click left-mouse-button. change the values in the inspector while playing, also change the position and rotation of the empty. The lines should show that the raycast is done relative to the objects forward.

 #pragma strict
 import System.Collections.Generic;
 
 public var radius : float = 5.0;
 public var segments : int = 12;
 public var curveAmount : float = 360.0;
 private var calcAngle : float;
 var nodes : List.< Vector3 > = new List.< Vector3 >(); // private , left out to check in inspector
 
 function Update() 
 {
     if ( Input.GetMouseButtonDown(0) )
     {
         CalculatePoints();        
         DrawLines();    // just for testing    
         CheckForHits();
     }
 }
 
 function CalculatePoints() 
 {
     nodes.Clear();
     calcAngle = 0;
     
     // Calculate Arc on Y-Z    
     for ( var i : int = 0; i < segments + 1; i ++ )
     {
         var posY : float = Mathf.Cos( calcAngle * Mathf.Deg2Rad ) * radius;
         var posZ : float = Mathf.Sin( calcAngle * Mathf.Deg2Rad ) * radius;            
         nodes.Add( transform.position + ( transform.up * posY ) + ( transform.forward * posZ ) );    
         calcAngle += curveAmount / parseFloat(segments);
     }
 }
 
 function CheckForHits() 
 {
     var hit : RaycastHit;
     for ( var i:int = 0; i < nodes.Count - 1; i ++ )
     {
         if ( Physics.Linecast( nodes[i], nodes[i + 1], hit ) )
         {
             Debug.Log( "Hit " + hit.collider.gameObject.name );
         }
     }
 }
 
 function DrawLines() 
 {
     for ( var i:int = 0; i < nodes.Count - 1; i ++ )
     {
         Debug.DrawLine( nodes[i], nodes[i + 1], Color.red, 1.5 );
     }
 }