unity 鼠标实时画箭头

pc端的QQ与微信截图里都有个拖拽鼠标画箭头的功能以至于好做标注，其实unity也可以实现这个功能，亲测在webgl端与pc端可用，移动端由于感觉没意义没测试，博主觉得应该没啥问题，主要思路就是：箭头由线段和图片组成，鼠标可以实时改变箭头长短和方向（箭头的方向我暂时只是在2维下画的，绕着z轴实时旋转就行，一点向量基础就行），鼠标按下出现一个三角箭头，鼠标滑动就绘制出线段，线段可跟着你的鼠标变长变短，变粗这块博主很苦恼（因为男人嘛都要粗）,由于最近一直在研究OpenGL，所以线段是用GL画的，性能这块没得说,dc不会随着线段的条数增加，unity没有提供变粗的方法，那就忍忍吧，bb了这么多看起来很厉害吧！来张图压压惊：

效果看了那就直接看脚本了？

using UnityEngine;
using System.Collections;
public class LinesGL : MonoBehaviour
{
    private  Shader shader;
    private static Material m;
    private GameObject g;//便于查看当前点的坐标信息
    public Vector3[] lp;//存储的点
    private Vector3 s;//开始点
    public GameObject JT;
    private GameObject go;
    private Vector3 Vxyz;
    void Start()
    {
        shader = Shader.Find("Yogi3/ImageEffect/Occlusion");
        m = new Material(shader);
        m.SetColor("_MainColor", new Color(1f, 0.01f, 0.1f, 1f));//修改shader颜色
        g = new GameObject("g");
        lp = new Vector3[0];
        Vxyz = new Vector3(2,0,0);//平行于X轴向量
    }

    void Update()
    {
        Vector3 e;//结束点
        if (Input.GetMouseButtonDown(0))
        {
            s = GetNewPoint();
            //显示的z轴看自己需求赋值，只要在相机前面就行
             go=Instantiate(JT, Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.transform.position.z * -1.0f) ), Quaternion.identity)as GameObject;
            
        }
        //拖拽便于确定箭头方向
        if (Input.GetMouseButton(0))
        {
            e = GetNewPoint();
            lp = AddLine(lp, s, e, true);
            go.transform.position = Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.transform.position.z * -1.0f));
            Vector3 Vangle = lp[lp.Length-1] - lp[lp.Length - 2];//最后一条线段
            float angle = Vector3.Angle(Vangle,Vxyz)-90;//三角箭头绕着Z轴旋转 那么就限制与X轴夹角为旋转角度吧
            if (Vangle.y > 0)
            {
                go.transform.eulerAngles = new Vector3(0, 0, angle);
            }
            else
            {
                go.transform.eulerAngles = new Vector3(0, 0, 180-angle);
            }
        }
        if (Input.GetMouseButtonUp(0))
        {
            e = GetNewPoint();
            lp = AddLine(lp, s, e, false);

        }
    }
    //判断最后一个点是否鼠标抬起确定了，确定了就存储起来，没有就删除，但是都会绘制出来（绘制了就删除刷新）
    Vector3[] AddLine(Vector3[] l, Vector3 s, Vector3 e, bool tmp)
    {
        int vl = l.Length;
        if (!tmp || vl == 0) l = resizeVertices(l, 2);
        else vl -= 2;

        l[vl] = s;
        l[vl + 1] = e;
        return l;
    }
    //处理拖拽的线条，实时更新
    Vector3[] resizeVertices(Vector3[] ovs, int ns)
    {
        Vector3[] nvs = new Vector3[ovs.Length + ns];
        for (int i = 0; i < ovs.Length; i++) nvs[i] = ovs[i];
        return nvs;
    }
    //反转坐标
    Vector3 GetNewPoint()
    {
        return g.transform.InverseTransformPoint(
            Camera.main.ScreenToWorldPoint(
                new Vector3(Input.mousePosition.x, Input.mousePosition.y, Camera.main.transform.position.z * -1.0f)
            )
        );
    }
    void OnPostRender()
    {
        m.SetPass(0);
        GL.PushMatrix();
        GL.MultMatrix(g.transform.transform.localToWorldMatrix);
        GL.Begin(GL.LINES);
        for (int i = 0; i < lp.Length; i++)
        {
            GL.Vertex3(lp[i].x, lp[i].y, lp[i].z);
        }
        GL.End();
        GL.PopMatrix();
    }

}

其实我想说说shader的在看看效果：

线段shader的是自己写的，图片的shader是默认的，是的没错，线段是透视的，不会被物体挡住的，但是会被UI挡住，最近迷上了图形学，捣鼓了大变天实现了屎样的效果，简直了，顺便贴出shader，

Shader "Yogi3/ImageEffect/Occlusion"  
{  
    Properties  
    {  
        _MainTex("Base (RGB)", 2D) = "white" {}  
        _DepthMap("DepthMap (RGB)", 2D) = "white" {}  
        _OcclusionMap("OcclusionMap (RGB)", 2D) = "white" {}  
        _Intensity("Intensity", Float) = 0.0  
        _Tiling("Tiling", Vector) = (1.0, 1.0, 0.0, 0.0)  
		_MainColor("MainsColor",Color)=(1,1,1,1)
    }  
  
    SubShader  
    {  
        Pass  
        {  
            ZTest Always  
            ZWrite Off  
            Cull Off  
            Fog{ Mode Off }  
  
            CGPROGRAM  
            #include "UnityCG.cginc"  
            #pragma vertex vert  
            #pragma fragment frag  
            #pragma fragmentoption ARB_precision_hint_fastest  
  
            sampler2D _MainTex;  
            sampler2D _DepthMap;  
            sampler2D _OcclusionMap;  
            sampler2D _CameraDepthNormalsTexture;  
            fixed4 _MainTex_TexelSize;  
            fixed _Intensity;  
            fixed _Power;  
            fixed4 _Tiling;  
			fixed4 _MainColor;

            struct a2v  
            {  
                fixed4 vertex : POSITION;  
                fixed2 texcoord : TEXCOORD0;  
            };  
  
            struct v2f  
            {  
                fixed4 vertex : SV_POSITION;  
                fixed2 uv : TEXCOORD0;  
            };  
  
            v2f vert(a2v v)  
            {  
                v2f o;  
                o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);  
                o.uv = v.texcoord.xy;  
  
                return o;  
            }  
  
            fixed4 frag(v2f i) : SV_Target  
            {  
                fixed4 c = tex2D(_MainTex, i.uv);  
  
                fixed4 depthMap = tex2D(_DepthMap, i.uv);  
                fixed depth = DecodeFloatRG(depthMap.zw);  
                fixed3 normal = DecodeViewNormalStereo(depthMap);  
  
                fixed4 cameraDepthMap = tex2D(_CameraDepthNormalsTexture, i.uv);  
                fixed cameraDepth = DecodeFloatRG(cameraDepthMap.zw);  
  
                fixed4 o = c;  
                if (depth > 0  
                    && cameraDepth < depth)  
                {  
                    fixed2 uv = i.uv * _Tiling.xy + _Tiling.zw;  
                    fixed3 color = tex2D(_OcclusionMap, uv);  
                    fixed nf = saturate(dot(normal, fixed3(0, 0, 1)));  
                    nf = pow(nf, _Intensity);  
                    o.rgb = lerp(color, c.rgb, nf)+_MainColor;  
                }  
				
                return _MainColor;  
				//return o;
            }  
  
            ENDCG  
        }  
    }  
  
    Fallback off  
}