Mathf.Infinity

public static float Infinity ;

説明

無限大を表現します（読み取り専用）

using UnityEngine;
using System.Collections;

public class ExampleClass : MonoBehaviour {
    void Update() {
        Debug.DrawLine(Vector3.zero, Vector3.forward * 100);
        if (Physics.Raycast(Vector3.zero, Vector3.forward, Mathf.Infinity))
            print("There is something in front of the object!");
        
    }
}