Unity shader学习之屏幕后期处理效果之边缘检测

边缘检测的原理是利用一些边缘检测算子对图像进行卷积操作。

转载请注明出处：http://www.cnblogs.com/jietian331/p/7232707.html

例如：

代码如下：

 using UnityEngine;

 public class EdgeDetectRenderer : PostEffectRenderer
 {
     [SerializeField]
     Color m_edgeColor;

     protected override void OnRenderImage(RenderTexture src, RenderTexture dest)
     {
         base.Mat.SetColor("_EdgeColor", m_edgeColor);
         base.OnRenderImage(src, dest);
     }

     protected override string ShaderName
     {
         get { return "Custom/Edge Detect"; }
     }
 }

EdgeDetectRenderer

shader如下：

 // Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

 Shader "Custom/Edge Detect"
 {
     Properties
     {
         _MainTex("Main Texture", 2D) = "white" {}
         _EdgeColor("Edge Color", Color) = (,,,)
     }

     SubShader
     {
         Pass
         {
             Cull Off
             ZWrite Off
             ZTest Always

             CGPROGRAM
             #pragma vertex vert
             #pragma fragment frag

             sampler2D _MainTex;
             float4 _MainTex_TexelSize;
             uniform fixed4 _EdgeColor;

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

             struct v2f
             {
                 float4 pos : SV_POSITION;
                 half2 uv[] : TEXCOORD0;
             };

             v2f vert(appdata v)
             {
                 v2f o;
                 o.pos = UnityObjectToClipPos(v.vertex);
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(-, );
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(, );
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(, );
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(-, );
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(, );
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(, );
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(-, -);
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(, -);
                 o.uv[] = v.uv + _MainTex_TexelSize.xy * half2(, -);
                 return o;
             }

             float luminance(float3 color)
             {
                 return dot(fixed3(0.2125, 0.7154, 0.0721), color);
             }

             half sober(half2 uvs[])
             {
                 half gx[] = {    -, , ,
                                 -, , ,
                                 -, , };
                 half gy[] = {    -, -, -,
                                 , , ,
                                 , , };

                 float edgeX = ;
                 float edgeY = ;

                 for(int i = ; i < ; i++)
                 {
                     fixed3 c = tex2D(_MainTex, uvs[i]).rgb;
                     float l = luminance(c);
                     edgeX += l * gx[i];
                     edgeY += l * gy[i];
                 }

                 return abs(edgeX) + abs(edgeY);
             }

             fixed4 frag(v2f i) : SV_TARGET
             {
                 half edge = sober(i.uv);
                 fixed4 tex = tex2D(_MainTex, i.uv[]);
                 return lerp(tex, _EdgeColor, edge);
             }

             ENDCG
         }
     }

     Fallback Off
 }

效果如下：