C for Graphic：CommandBuffer透视镜

       最近和深圳老同事聊天，感觉都老惨了，本身都是做游戏出生，结果游戏公司版号、资本问题搞的各种花式降薪裁员，玩的比较好的一个同事找工作千难万难最后面进了一个VR公司，做医疗手术类型VR程序。功能中要做一个透视镜效果，他搞不定，让我帮忙解决，因为刚好用commandbuffer来做就很简单，所有记录一下。

       要求功能就是有一个检测仪，扫描人体皮肤表面可以观察到内部骨骼的x光渲染画面，话说有这种仪器吗？

       不过这种效果不算复杂，我们以前也都学习过，无非就是几种效果原理的叠加组合而已：

       1.网格边缘光

       2.采样纹理

       3.裁剪纹理

       首先我们给一个模型网格做一个透视遮挡边缘光的效果：

Shader "XRay/XRayColorShader"
{
    Properties
    {
       _MainColor("X Ray Color",Color) = (1,1,1,1)
       _MainOffset("X Ray Light Offset",Range(-1,1)) = 0
    }
    SubShader
    {
        Tags { "RenderType"="Transparent" "Queue"="Transparent" }
        LOD 100

        Pass
        {
            Blend SrcAlpha OneMinusSrcAlpha
            ZTest Greater ZWrite Off
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float4 normal : NORMAL;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float3 worldP2V : TEXCOORD0;
                float3 worldNm : TEXCOORD1;
            };

            float4 _MainColor;
            float _MainOffset;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.worldP2V = normalize(WorldSpaceViewDir(v.vertex));
                o.worldNm = normalize(UnityObjectToWorldNormal(v.normal.xyz));
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                float wei = 1 - saturate(dot(i.worldP2V,i.worldNm) + _MainOffset);
                fixed4 col = fixed4(_MainColor.rgb,wei);
                return col;
            }
            ENDCG
        }
    }
}

        效果如下：

 

       然后我们通过commandbuffer将效果提取到“屏幕”上，如下：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.Rendering;

public class CmdBufferXRayCamera : MonoBehaviour
{
    public GameObject[] cmdObjects;
    public Material xrayMat;

    private RenderTexture objectRT = null;
    private CommandBuffer cmdBuffer = null;

    void Start()
    {

    }

    private void OnEnable()
    {
        objectRT = RenderTexture.GetTemporary(Screen.width, Screen.height, 0, RenderTextureFormat.ARGB32);
        cmdBuffer = new CommandBuffer();
        cmdBuffer.SetRenderTarget(objectRT);
        cmdBuffer.ClearRenderTarget(true, true, Color.black);
        for (int i = 0; i < cmdObjects.Length; i++)
        {
            GameObject go = cmdObjects[i];
            MeshRenderer render = go.GetComponent<MeshRenderer>();
            if (render != null)
            {
                cmdBuffer.DrawRenderer(render, xrayMat);
            }
        }
        Camera.main.AddCommandBuffer(CameraEvent.AfterImageEffects, cmdBuffer);
    }

    private void OnDisable()
    {
        RenderTexture.ReleaseTemporary(objectRT);
        objectRT = null;

        Camera.main.RemoveCommandBuffer(CameraEvent.AfterImageEffects, cmdBuffer);
        cmdBuffer.Clear();
        cmdBuffer = null;
    }

    private void OnRenderImage(RenderTexture source, RenderTexture destination)
    {
        if (cmdBuffer != null)
        {
            Graphics.ExecuteCommandBuffer(cmdBuffer);
        }

        Graphics.Blit(objectRT, destination);
    }
}

       效果如下：

 

        最后做一个屏幕上的透视镜圆环采样叠加功能：

Shader "XRay/LensCircleShader"
{
    Properties
    {
        _SrcTex ("Source Tex", 2D) = "white" {}
        _XRayTex("X Ray Tex",2D) = "white" {}
        _UV("Lens UV Saturate",vector) = (0,0,0,0)
        _LensColor("Lens Outside Color",Color) = (1,1,1,1)
        _Radius("Lens Inside Radius",Range(0,1)) = 0.1
        _Width("Lens Outside Width",Range(0,1)) = 0.05
        _Aspect("Screen Height / Width",float) = 1
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag

            #include "UnityCG.cginc"

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
                float4 vertex : SV_POSITION;
            };

            sampler2D _SrcTex;
            float4 _SrcTex_ST;
            sampler2D _XRayTex;

            vector _UV;
            float4 _LensColor;
            float _Radius;
            float _Width;

            float _Aspect;

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = TRANSFORM_TEX(v.uv, _SrcTex);
                return o;
            }

            fixed4 frag (v2f i) : SV_Target
            {
                fixed4 scol = tex2D(_SrcTex, i.uv);
                fixed4 xcol = tex2D(_XRayTex,i.uv);
                fixed4 col;
                float2 p2c = float2(i.uv - float2(_UV.x,_UV.y));
                float p2clen2 = p2c.x*p2c.x+p2c.y*_Aspect*p2c.y*_Aspect;
                float radius2 = _Radius*_Radius;
                float outradius2 = (_Radius+_Width)*(_Radius+_Width);
                if(p2clen2>outradius2)
                {
                    xcol = fixed4(0,0,0,0);
                }
                else if(p2clen2<outradius2 && p2clen2>radius2)
                {
                    col = _LensColor;
                    return col;
                }
                col = saturate(scol + xcol);
                return col;
            }
            ENDCG
        }
    }
}

        shader功能也简单，获取两张纹理，然后通过圆环InsideRadius和OutsideRadius进行裁剪叠加，c#代码控制一下功能性：

using System.Collections;
using System.Collections.Generic;
using System.Security.Cryptography;
using UnityEngine;
using UnityEngine.Rendering;

public class CmdBufferXRayCamera : MonoBehaviour
{
    public GameObject[] cmdObjects;
    public Material xrayMat;
    public Material lensMat;

    private RenderTexture objectRT = null;
    private CommandBuffer cmdBuffer = null;

    void Start()
    {
        lensMat.SetFloat("_Aspect", (float)Screen.height / (float)Screen.width);
    }

    private void OnEnable()
    {
        objectRT = RenderTexture.GetTemporary(Screen.width, Screen.height, 0, RenderTextureFormat.ARGB32);
        cmdBuffer = new CommandBuffer();
        cmdBuffer.SetRenderTarget(objectRT);
        cmdBuffer.ClearRenderTarget(true, true, Color.black);
        for (int i = 0; i < cmdObjects.Length; i++)
        {
            GameObject go = cmdObjects[i];
            MeshRenderer render = go.GetComponent<MeshRenderer>();
            if (render != null)
            {
                cmdBuffer.DrawRenderer(render, xrayMat);
            }
        }
        Camera.main.AddCommandBuffer(CameraEvent.AfterForwardOpaque, cmdBuffer);
    }

    private void OnDisable()
    {
        RenderTexture.ReleaseTemporary(objectRT);
        objectRT = null;

        Camera.main.RemoveCommandBuffer(CameraEvent.AfterForwardOpaque, cmdBuffer);
        cmdBuffer.Clear();
        cmdBuffer = null;
    }

    private void OnRenderImage(RenderTexture source, RenderTexture destination)
    {
        if (cmdBuffer != null)
        {
            Graphics.ExecuteCommandBuffer(cmdBuffer);
        }

        lensMat.SetTexture("_SrcTex", source);
        lensMat.SetTexture("_XRayTex", objectRT);

        Graphics.Blit(null, destination, lensMat);
    }

    private void Update()
    {
        if(Input.GetMouseButton(0))
        {
            Vector2 mpos = Input.mousePosition;
            Vector4 uv = new Vector4(mpos.x / Screen.width, mpos.y / Screen.height);
            lensMat.SetVector("_UV", uv);
        }
    }
}

        效果如下：

  

          so，因为以前也学过这些原理，所以只简单记录一下。