后處理之輝光效果

這是我在《游戲架構-核心技術與面試精粹》看的蟆技，記錄一下~

泛光和輝光不一樣么汰现？
那是肯定的

輝光（Glow）：是全屏泛光的升級版本
區(qū)別就是輝光要求場景內(nèi)只有部分物體泛光，而不是全部泛光
所以需要區(qū)分出忽略那些物體

大體思路：
1.用一個額外的攝像機給，在這個攝像機下宴合，所有的非泛光物體都是黑色的，泛光物體保持原樣
2.再將這個結果渲染到一個 RT 上迹鹅，對他進行模糊
3.最后將模糊后的反光圖疊加到主攝像機的渲染圖像上

創(chuàng)建一個 LightGeometry.shader
默認的surface shader卦洽，改了 RenderType
RenderType 可以使用自定義名稱，并不會對改 shader 的使用和著色器產(chǎn)生影響
需要自己區(qū)別場景中不同渲染對象使用的 Shader 的 RenderType 的類型名稱不同

Shader "Custom/LightGeometry"
{
    Properties
    {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _Glossiness ("Smoothness", Range(0,1)) = 0.5
        _Metallic ("Metallic", Range(0,1)) = 0.0
    }
    SubShader
    {
        Tags { "RenderType"="Glow" } //只改了這里
        LOD 200

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        sampler2D _MainTex;

        struct Input
        {
            float2 uv_MainTex;
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
        UNITY_INSTANCING_BUFFER_START(Props)
            // put more per-instance properties here
        UNITY_INSTANCING_BUFFER_END(Props)

        void surf (Input IN, inout SurfaceOutputStandard o)
        {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
            o.Albedo = c.rgb;
            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }
    FallBack "Diffuse"
}

在相機那邊斜棚，可以通過該函數(shù) 動態(tài)替換攝像機下物體的 shader

 GetComponent<Camera>().RenderWithShader(replaceShader, "RenderType");

當調(diào)用 RenderWithShader 是阀蒂，會檢查攝像機下的每個物體的 RenderTag
（通常選取 Tag 的條件都是 RenderType）

替換的過程：
1.遍歷所有要顯示的物體
2.如果物體的 Shader 與傳入的 replaceShader 有相同的 RenderType
3.則用 replaceShader 的響應 subshader 替換

下面的 shader该窗，增加了一個 subshader
用來將 RenderType 為 Opaque 的物體替換成為黑色，而為 Glow 的內(nèi)容保持不變
（不發(fā)光的物體要繪制呈黑色蚤霞，避免遮擋關系會出錯）

Shader "Custom/RenderGlowRT"
{
    Properties
    {
        _Color ("Color", Color) = (1,1,1,1)
        _MainTex ("Albedo (RGB)", 2D) = "white" {}
        _Glossiness ("Smoothness", Range(0,1)) = 0.5
        _Metallic ("Metallic", Range(0,1)) = 0.0
    }
    SubShader
    {
        Tags { "RenderType"="Glow" }
        LOD 200

        CGPROGRAM
        // Physically based Standard lighting model, and enable shadows on all light types
        #pragma surface surf Standard fullforwardshadows

        // Use shader model 3.0 target, to get nicer looking lighting
        #pragma target 3.0

        sampler2D _MainTex;

        struct Input
        {
            float2 uv_MainTex;
        };

        half _Glossiness;
        half _Metallic;
        fixed4 _Color;

        // Add instancing support for this shader. You need to check 'Enable Instancing' on materials that use the shader.
        // See https://docs.unity3d.com/Manual/GPUInstancing.html for more information about instancing.
        // #pragma instancing_options assumeuniformscaling
        UNITY_INSTANCING_BUFFER_START(Props)
            // put more per-instance properties here
        UNITY_INSTANCING_BUFFER_END(Props)

        void surf (Input IN, inout SurfaceOutputStandard o)
        {
            // Albedo comes from a texture tinted by color
            fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
            o.Albedo = c.rgb;
            // Metallic and smoothness come from slider variables
            o.Metallic = _Metallic;
            o.Smoothness = _Glossiness;
            o.Alpha = c.a;
        }
        ENDCG
    }

    SubShader
    {
        Tags {"RenderType" = "Opaque"}
        LOD 200

        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 _MainTex;
            float4 _MainTex_ST;

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

            fixed4 frag(v2f i) : SV_TARGET
            {
                fixed4 col = fixed4(0, 0, 0, 1);
                return col;
            }

            ENDCG
        }
    }

    FallBack "Diffuse"
}

再創(chuàng)建一個 CustomGlow.cs 腳本酗失，負責：
1.在主攝像機下創(chuàng)建了參數(shù)相同的子攝像機
2.并把這個攝像機的渲染目標設置為內(nèi)存中的一個 RenderTextrue
3.渲染時，通過 RenderImage 將其與主攝像機的內(nèi)容進行混合
4.使用 RenderWithShader 實現(xiàn)特效時争便，應該將相機設為disable级零，防止影響原圖的繪制

public class CustomGlow : MonoBehaviour
{
    public Shader renderGlowShader;
    public Material blurMaterial;
    public Material mixMaterial;

    private RenderTexture rt;


    private void Start()
    {
        Camera mainCam = GetComponent<Camera>();

        this.rt = new RenderTexture(Screen.width, Screen.height, (int)mainCam.depth);

        GameObject go = new GameObject("CameraRT");
        go.transform.SetParent(transform, false);

        Camera cam = go.AddComponent<Camera>();
        cam.enabled = false;
        cam.clearFlags = CameraClearFlags.SolidColor;
        cam.backgroundColor = Color.black;
        cam.orthographic = mainCam.orthographic;
        cam.orthographicSize = mainCam.orthographicSize;
        cam.nearClipPlane = mainCam.nearClipPlane;
        cam.farClipPlane = mainCam.farClipPlane;
        cam.fieldOfView = mainCam.fieldOfView;
        cam.fieldOfView = mainCam.fieldOfView;
        cam.targetTexture = rt;

        RenderPostEffect bloomTex = go.AddComponent<RenderPostEffect>();
        bloomTex.replaceShader = renderGlowShader;
        bloomTex.renderMaterial = blurMaterial;

        mixMaterial.SetTexture("_BlurTex", rt);
    }

    private void OnRenderImage(RenderTexture source, RenderTexture destination)
    {
        Graphics.Blit(source, destination, mixMaterial);
    }
}

最后創(chuàng)建一個 mixTexture.shader 文件

Shader "Custom/MixTexture"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
        _BlurTex ("Blur Textrue", 2D) = "White" {}
        _BlurFactor ("Blur Factor", Range(0, 1)) = 0.5
    }
    SubShader
    {
        Tags { "RenderType"="Opaque" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            // make fog work
            #pragma multi_compile_fog

            #include "UnityCG.cginc"

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

            struct v2f
            {
                float2 uv : TEXCOORD0;
                UNITY_FOG_COORDS(1)
                float4 vertex : SV_POSITION;
            };

            sampler2D _MainTex;
            float4 _MainTex_ST;

            sampler2D _BlurTex;
            float4 _BlurTex_ST;

            float _BlurFactor;

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

            fixed4 frag (v2f i) : SV_Target
            {
                // sample the texture
                fixed4 col = tex2D(_MainTex, i.uv);
                fixed4 blur = tex2D(_BlurTex, i.uv);
                fixed4 final = col + blur * _BlurFactor;
                // apply fog
                UNITY_APPLY_FOG(i.fogCoord, final);
                return final ;
            }
            ENDCG
        }
    }
}

最后把它掛到相機上，掛到相機上：