U3D准星

using UnityEngine;
using System.Collections;

public class DrawStar : MonoBehaviour {

public Material _mat;
public Color _starColor;

const float minDistance = 1.5f;
const float maxDistance = 8f;

public float length = 2.5f;
float distance = minDistance;

public float increaseSpeed = 5f;

Vector2[] offset;

private void Start()
{
offset = new Vector2[16];
}

private void Update()
{
if (Input.GetMouseButton(0))
{
distance += Time.deltaTime * increaseSpeed;
}
else
{
distance -= Time.deltaTime * increaseSpeed;
}

if (distance< minDistance)
{
distance = minDistance;
}
else if (distance>maxDistance)
{
distance = maxDistance;
}

}

private void OnPostRender()
{
DrawLine(Input.mousePosition);
}

void DrawLine(Vector2 center)
{
GL.PushMatrix();
_mat.SetPass(0);
GL.LoadOrtho();
GL.Begin(GL.LINES);
GL.Color(_starColor);

offset[0] = new Vector2(-distance - length, distance);
offset[1] = new Vector2(-distance, distance);
offset[2] = new Vector2(distance + length, distance);
offset[3] = new Vector2(distance, distance);

for (int j = 0; j < 2; j++)
{
int isY = j % 2 == 0 ? 1 : -1;
for (int i = 0; i < 4; i += 2)
{
int isX = i % 4 > 1 ? 1 : -1;
offset[j * 4 + i] = new Vector2(isX * (distance + length), isY * distance);
offset[j * 4 + i + 1] = new Vector2(isX * distance, isY * distance);
}
}

for (int i = 0; i < 8; i++)
{
offset[i + 8].x = offset[i].y;
offset[i + 8].y = offset[i].x;
}

for (int i = 0; i < offset.Length; i+=2)
{
DrawLine(center + offset[i], center + offset[i + 1]);
}

GL.End();
GL.PopMatrix();

}

void DrawLine(Vector2 start,Vector2 end)
{
GL.Vertex3(start.x / Screen.width, start.y / Screen.height, 0);
GL.Vertex3(end.x / Screen.width, end.y / Screen.height, 0);
}
}