第十二章 边缘检测

PostEffectsBase.cs

using UnityEngine;
using System.Collections;

[ExecuteInEditMode]
[RequireComponent (typeof(Camera))]
public class PostEffectsBase : MonoBehaviour {

    // Called when start
    protected void CheckResources() {
        bool isSupported = CheckSupport();
        
        if (isSupported == false) {
            NotSupported();
        }
    }

    // Called in CheckResources to check support on this platform
    protected bool CheckSupport() {
        if (SystemInfo.supportsImageEffects == false || SystemInfo.supportsRenderTextures == false) {
            Debug.LogWarning("This platform does not support image effects or render textures.");
            return false;
        }
        
        return true;
    }

    // Called when the platform doesn't support this effect
    protected void NotSupported() {
        enabled = false;
    }
    
    protected void Start() {
        CheckResources();
    }

    // Called when need to create the material used by this effect
    protected Material CheckShaderAndCreateMaterial(Shader shader, Material material) {
        if (shader == null) {
            return null;
        }
        
        if (shader.isSupported && material && material.shader == shader)
            return material;
        
        if (!shader.isSupported) {
            return null;
        }
        else {
            material = new Material(shader);
            material.hideFlags = HideFlags.DontSave;
            if (material)
                return material;
            else 
                return null;
        }
    }
}

EdgeDetection.cs

using UnityEngine;
using System.Collections;

public class EdgeDetection : PostEffectsBase {

    public Shader edgeDetectShader;
    private Material edgeDetectMaterial = null;
    public Material material {  
        get {
            edgeDetectMaterial = CheckShaderAndCreateMaterial(edgeDetectShader, edgeDetectMaterial);
            return edgeDetectMaterial;
        }  
    }

    [Range(0.0f, 1.0f)]
    public float edgesOnly = 0.0f;

    public Color edgeColor = Color.black;
    
    public Color backgroundColor = Color.white;

    void OnRenderImage (RenderTexture src, RenderTexture dest) {
        if (material != null) {
            material.SetFloat("_EdgeOnly", edgesOnly);
            material.SetColor("_EdgeColor", edgeColor);
            material.SetColor("_BackgroundColor", backgroundColor);

            Graphics.Blit(src, dest, material);
        } else {
            Graphics.Blit(src, dest);
        }
    }
}

内置渲染管线

Shader "SunY/C12-EdgeDetection"
{
    Properties
    {
        _MainTex("Main Tex" , 2D) = "white"{}
        _EdgeOnly("Edge Only", float) = 1
        _EdgeColor("Edge Color", Color) = (1, 1, 1, 1)
        _BackgroundColor("Background Color", Color) = (1, 1, 1, 1)
    }

    SubShader
    {
        Pass
        {
            ZTest Always
            ZWrite Off
            Cull Off

            CGPROGRAM

            #include "UnityCG.cginc"

            #pragma vertex vert
            #pragma fragment frag

            sampler2D _MainTex;
            half4 _MainTex_TexelSize;
            float _EdgeOnly;
            fixed4 _EdgeColor;
            fixed4 _BackgroundColor;

            struct v2f
            {
                float4 pos : SV_POSITION;
                half2 uv[9] : TEXCOORD0;
            };

            v2f vert(appdata_img v)
            {
                v2f o;

                o.pos = UnityObjectToClipPos(v.vertex);

                half2 uv = v.texcoord;

                // 顶点着色器计算邻域采样纹理坐标可以减少运算，提高性能，顶点着色器到片元着色器是线性插件，不会影响最终结果
                o.uv[0] = uv + _MainTex_TexelSize.xy * half2(-1, -1);
                o.uv[1] = uv + _MainTex_TexelSize.xy * half2(0, -1);
                o.uv[2] = uv + _MainTex_TexelSize.xy * half2(1, -1);
                o.uv[3] = uv + _MainTex_TexelSize.xy * half2(-1, 0);
                o.uv[4] = uv + _MainTex_TexelSize.xy * half2(0, 0);
                o.uv[5] = uv + _MainTex_TexelSize.xy * half2(1, 0);
                o.uv[6] = uv + _MainTex_TexelSize.xy * half2(-1, 1);
                o.uv[7] = uv + _MainTex_TexelSize.xy * half2(0, 1);
                o.uv[8] = uv + _MainTex_TexelSize.xy * half2(1, 1);

                return o;
            }

            fixed luminance(fixed4 color)
            {
                return 0.2125 * color.r + 0.7154 * color.g + 0.0721 * color.b;
            }

            half Sobel(v2f i)
            {
                const half Gx[9] = {-1, 0, 1, -2, 0, 2, -1, 0, 1};
                const half Gy[9] = {-1, -2, -1, 0, 0, 0, 1, 2, 1};

                half texColor;
                half edgeX = 0;
                half edgeY = 0;
                for(int it = 0; it < 9; it++)
                {
                    texColor = luminance(tex2D(_MainTex, i.uv[it]));
                    edgeX += texColor * Gx[it];
                    edgeY += texColor * Gy[it];
                }

                half edge = 1 - abs(edgeX) - abs(edgeY);

                return edge;
            }

            fixed4 frag(v2f i): SV_Target
            {
                half edge = Sobel(i);

                fixed4 withEdgeColor = lerp(_EdgeColor, tex2D(_MainTex, i.uv[4]), edge);
                fixed4 onlyEdgeColor = lerp(_EdgeColor, _BackgroundColor, edge);
                return lerp(withEdgeColor, onlyEdgeColor, _EdgeOnly);
            }

            ENDCG
        }
    }

    FallBack Off
}