极简 RenderFeature 案例#

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Shader "Hidden/GrayScale"
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{
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    SubShader
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    {
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        Tags
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        {
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            "RenderPipeline" = "UniversalPipeline"
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            "RenderType" = "Opaque"
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        }
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        Pass
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        {
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            Name "GrayScale"
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            HLSLPROGRAM
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            #pragma vertex vert
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            #pragma fragment frag
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            #include "Packages/com.unity.render-pipelines.universal/ShaderLibrary/Core.hlsl"
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            struct Attributes
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            {
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                // 直接告诉 Shader：你现在正在处理第几个顶点
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                uint vertexID : SV_VertexID;
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            };
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            struct Varyings
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            {
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                float4 positionHCS : SV_POSITION;
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                float2 uv : TEXCOORD0;
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            };
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            TEXTURE2D_X(_BlitTexture);
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            SAMPLER(sampler_BlitTexture);
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            Varyings vert(Attributes input)
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            {
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                Varyings output;
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                output.positionHCS = GetFullScreenTriangleVertexPosition(input.vertexID);
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                output.uv = GetFullScreenTriangleTexCoord(input.vertexID);
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                return output;
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            }
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            half4 frag(Varyings input) : SV_Target
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            {
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                half4 color = SAMPLE_TEXTURE2D_X(_BlitTexture,sampler_BlitTexture,input.uv);
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                // 把 RGB 三个颜色值，按照不同的重要程度加权，计算出一个灰度值。
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                half gray = dot(color.rgb,half3(0.299,0.587,0.114));
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                return half4(gray,gray,gray,color.a);
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            }
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            ENDHLSL
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        }
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    }
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}

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using UnityEngine;
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using UnityEngine.Rendering;
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using UnityEngine.Rendering.Universal;
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public class GrayScaleRF : ScriptableRendererFeature
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{
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    class GrayScalePass : ScriptableRenderPass
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    {
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        private Material material;
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        private RTHandle cameraColorTarget;
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        private RTHandle temporaryRT;
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        public GrayScalePass(Material material)
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        {
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            this.material = material;
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        }
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        // 使用专门的函数进行初始化，让代码更加规整
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        public void SetTarget(RTHandle target)
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        {
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            cameraColorTarget = target;
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        }
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        public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
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        {
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            RenderTextureDescriptor descriptor = renderingData.cameraData.cameraTargetDescriptor;
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            descriptor.depthBufferBits = 0;
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            RenderingUtils.ReAllocateIfNeeded(ref temporaryRT, descriptor, FilterMode.Point, TextureWrapMode.Clamp,
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                name: "_GrayScaleTemp");
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        }
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        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
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        {
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            if(material == null) return;
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            CommandBuffer cmd = CommandBufferPool.Get("GrayScale");
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            // Camera -> 临时 RT
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            Blitter.BlitCameraTexture(cmd,cameraColorTarget,temporaryRT);
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            // 临时RT -> Camera
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            Blitter.BlitCameraTexture(cmd,temporaryRT,cameraColorTarget,material,0);
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            context.ExecuteCommandBuffer(cmd);
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            CommandBufferPool.Release(cmd);
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        }
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        // 实际开发中实际不太会用 OnCameraCleanup，而是使用 Dispose，与 RF 的 Dispose 一起调用。
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        public void Dispose()
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        {
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            temporaryRT?.Release();
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            temporaryRT =  null;
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        }
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    }
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    [SerializeField] private Material material;
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    private GrayScalePass pass;
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    public override void Create()
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    {
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        pass = new GrayScalePass(material);
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        pass.renderPassEvent = RenderPassEvent.BeforeRenderingPostProcessing;
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    }
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    // 在 AddRenderPasses 之前执行，SetTarget 应该在此方法中进行配置
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    public override void SetupRenderPasses(ScriptableRenderer renderer, in RenderingData renderingData)
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    {
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        if(material == null)
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            return;
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        if(renderingData.cameraData.cameraType != CameraType.Game) return;
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        pass.SetTarget(renderer.cameraColorTargetHandle);
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    }
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    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
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    {
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        if(material == null)
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            return;
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        if(renderingData.cameraData.cameraType != CameraType.Game) return;
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        renderer.EnqueuePass(pass);
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    }
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    protected override void Dispose(bool disposing)
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    {
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        pass?.Dispose();
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    }
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}