获取相机内容，实现分屏效果小测试

获取相机内容，实现分屏效果

场景搭建：

1、场景中包括2个相机：main Camera 作为主相机拍摄游戏画面。再创建一个相机camera用于拍摄另一个屏幕内容，background的Alpha通道值设为0，保证背景透明。

2、创建一个quad作为画面显示面板。创建一个cube作为camera显示内容。

3、创建一个C#脚本FogOfWarRenderTex.cs。用于将camera渲染的画面显示到quad的shader中_MainTex1上。代码如下：

using UnityEngine;

using System.Collections;

//[ExecuteInEditMode]

//[RequireComponent (typeof(Camera))]   

public class FogOfWarRenderTex : MonoBehaviour

{

    RenderTexture renderTex;  //该相机渲染出的纹理

    Camera camera;    //渲染用的相机

    GameObject quad;  //渲染到指定面片上

    GameObject cube;  //需要被渲染的对象

    // Use this for initialization

    void Start()

    {

        renderTex = new RenderTexture(200, 200, 16, RenderTextureFormat.Default);  //创建一个新的RenderTexture

        cube = GameObject.CreatePrimitive(PrimitiveType.Cube);

        cube.transform.position = new Vector3(0, 0, 1);

        cube.layer =  31;

        quad = GameObject.CreatePrimitive(PrimitiveType.Quad);

        quad.transform.position = new Vector3(2, 0, 2);

        quad.name = "quad";

        camera = new GameObject("NPCCamera").AddComponent<Camera>();

        camera.targetTexture = renderTex;          //相机的目标纹理赋值        

        camera.transform.position = new Vector3(0, 0, 0);

        camera.clearFlags = CameraClearFlags.Color;

        camera.backgroundColor =new Color(0,0,0,0); 

        camera.cullingMask = 1<<31;

        camera.orthographic = true;

        camera.orthographicSize = 1;

        camera.nearClipPlane = 0.3f;

        camera.farClipPlane = 10f;

        //Shader.SetGlobalTexture("_MainTex1", camera.targetTexture);       //给全局shader中的纹理_MainTex1赋值，所有使用该shader的物体都会显示相机渲染的画面

        quad.GetComponent<MeshRenderer>().material = new Material(Shader.Find("LT/NPC_UI"));

        quad.GetComponent<MeshRenderer>().sharedMaterial.mainTexture = renderTex;

        quad.GetComponent<MeshRenderer>().sharedMaterial.SetColor("_MainColor",Color.white) ;

        //GameObject obj = Instantiate(quad, new Vector3(0, 0, 0),Quaternion.identity) as GameObject;

    }

 

}

创建一个简单的透明的包含_MainTex1属性的shader（该属性可不显示到Properties），将此shader指定到plane。

Shader "LT/Unlit2"
{
    Properties
    {
        _MainColor ("MainColor", COLOR) = (0.5,0.5,0.5,1.0)
//        _MainTex1("Main Texture",2D) = "while" {}    //该属性可不显示到Properties
    }
    SubShader
    {
            Tags{"Queue" = "Transparent" "RnderType" = "Transparent" "IgnorProjection" = "true"}
    
        Pass
        {
            ZWrite off
            Blend SrcAlpha OneMinusSrcAlpha
            
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #include "UnityCG.cginc"

            fixed4 _MainColor;
            sampler2D _MainTex1;
            float4 _MainTex1_ST;
            float _Red;

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };
            
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = mul(UNITY_MATRIX_MVP, v.vertex);

                o.uv = TRANSFORM_TEX(v.uv,_MainTex1);           
                return o;
            }
            
            fixed4 frag (v2f i) : SV_Target
            {
                // sample the texture
                fixed4 col =tex2D(_MainTex1,i.uv)* _MainColor;   
                return col;
            }
            ENDCG
        }
    }
}