Question

JavaScript => public var fraction: float;
C# => public float fraction;

Description 描述

Fraction of the distance along the ray that the hit occurred.

射线发生碰撞距离的百分比。

If the ray's direction vector is normalised then this value is simply the distance between the origin and the hit point. If the direction is not normalised then this distance is expressed as a “fraction” (which could be greater than 1) of the vector's magnitude.

这句话官方说的有问题，这个值和方向的大小无关的。实际测试，该值表示射线碰到对象的距离与射线长度的比值。

See Also: point.

JavaScript:

#pragma strict
public var direction;
function Update() {
	//Cast a ray in the direction specified in the inspector.
	var hit = Physics2D.Raycast(this.gameObject.transform.position, direction, 10.0f);
	//If something was hit.
	if (hit.collider != null) {
		Debug.Log(hit.fraction);
	}
}

C#:

using UnityEngine;
using System.Collections;
 
public class ExampleClass : MonoBehaviour
{
	public Vector2 direction;
 
	void Update()
	{
		//Cast a ray in the direction specified in the inspector.
		RaycastHit2D hit = Physics2D.Raycast(this.gameObject.transform.position,direction,10.0f);
 
		//If something was hit.
		if ( hit.collider != null )
		{
			Debug.Log(hit.fraction);
		}
	}
}

RaycastHit2D