URP下Alpha从Gamma空间到Linner空间转换（二）——多Alpha贴图叠加_unity gamma 转linner

使用后处理进行一次GammaToLinner的转换，能达到正确效果

URP 下取消勾选贴图SRGB,

后处理脚本

using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class CameraFeature : ScriptableRendererFeature
{
    public Material Material; //UniversalRenderPipelineAsset_Renderer 面板，设置材质
    private MyVolumeFeaturePass myPass;

    public override void Create()
    {
        myPass = new MyVolumeFeaturePass();
        myPass.renderPassEvent = RenderPassEvent.AfterRenderingTransparents;
    }


    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        renderer.EnqueuePass(myPass);
        myPass.SetValue(renderer.cameraColorTarget, Material); //传递摄像机图像，和材质，给Pass 处理
    }

    public class MyVolumeFeaturePass : ScriptableRenderPass
    {

        // This method is called before executing the render pass.
        // It can be used to configure render targets and their clear state. Also to create temporary render target textures.
        // When empty this render pass will render to the active camera render target.
        // You should never call CommandBuffer.SetRenderTarget. Instead call <c>ConfigureTarget</c> and <c>ConfigureClear</c>.
        // The render pipeline will ensure target setup and clearing happens in a performant manner.
        public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
        {


        }

        private Material Material;//接受从Feature 面板设置的材质
        private RenderTargetIdentifier source;//接受相机图像

        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
        {
            //if (renderingData.cameraData.camera.name != "UIMainCamera")
            //{
            //    return;
            //}
            //执行后处理
            if (Material == null)
            {
                return;
            }
            CommandBuffer cmd = CommandBufferPool.Get();
            //source  //源图像
            var dec = renderingData.cameraData.cameraTargetDescriptor; //目标图像
            RenderTargetHandle tempTargetHandle = new RenderTargetHandle();
            cmd.GetTemporaryRT(tempTargetHandle.id, dec);

            cmd.Blit(source, tempTargetHandle.Identifier(), Material);
            //核心命令CommandBuffer
            cmd.Blit(tempTargetHandle.Identifier(), source); //相当于 Graphics.Blit

            context.ExecuteCommandBuffer(cmd);
            CommandBufferPool.Release(cmd);
        }

        public void SetValue(RenderTargetIdentifier source, Material material)
        {
            Material = material; //接受面板材质
            this.source = source;
        }
    }
}

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多重后处理问题

因为没有指定UI相机，导致所有相机画面重复被转换，需要指定仅UI相机进行GammaToLinner转换（也可以在所有渲染之后对图像进行一次GammaToLinner转换）

在Execute函数中暴露相机名在面板上进行填写，判断是否是指定相机，不是指定相机，不进行后处理

			//判断是否是指定相机
            if (renderingData.cameraData.camera.name != cameraName)
            {
                return;
            }
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在Redner Feature 面板填入相机名

效果对比

完整参考代码

CameraFeature

using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.Universal;

public class CameraFeature : ScriptableRendererFeature
{
    public Material Material; //UniversalRenderPipelineAsset_Renderer 面板，设置材质
    private MyVolumeFeaturePass myPass;
    public string CameraName="";
    public override void Create()
    {
        myPass = new MyVolumeFeaturePass();
        myPass.renderPassEvent = RenderPassEvent.AfterRenderingTransparents;
    }


    public override void AddRenderPasses(ScriptableRenderer renderer, ref RenderingData renderingData)
    {
        renderer.EnqueuePass(myPass);
        myPass.SetValue(renderer.cameraColorTarget, Material, CameraName); //传递摄像机图像，和材质，给Pass 处理
    }

    public class MyVolumeFeaturePass : ScriptableRenderPass
    {

        // This method is called before executing the render pass.
        // It can be used to configure render targets and their clear state. Also to create temporary render target textures.
        // When empty this render pass will render to the active camera render target.
        // You should never call CommandBuffer.SetRenderTarget. Instead call <c>ConfigureTarget</c> and <c>ConfigureClear</c>.
        // The render pipeline will ensure target setup and clearing happens in a performant manner.
        public override void OnCameraSetup(CommandBuffer cmd, ref RenderingData renderingData)
        {


        }

        private Material material;//接受从Feature 面板设置的材质
        private RenderTargetIdentifier source;//接受相机图像
        private string cameraName;
        public override void Execute(ScriptableRenderContext context, ref RenderingData renderingData)
        {
            //判断是否是指定相机
            if (renderingData.cameraData.camera.name != cameraName)
            {
                return;
            }
            //执行后处理
            if (material == null)
            {
                return;
            }
            CommandBuffer cmd = CommandBufferPool.Get();
            //source  //源图像
            var dec = renderingData.cameraData.cameraTargetDescriptor; //目标图像
            RenderTargetHandle tempTargetHandle = new RenderTargetHandle();
            cmd.GetTemporaryRT(tempTargetHandle.id, dec);

            cmd.Blit(source, tempTargetHandle.Identifier(), material);
            //核心命令CommandBuffer
            cmd.Blit(tempTargetHandle.Identifier(), source); //相当于 Graphics.Blit

            context.ExecuteCommandBuffer(cmd);
            CommandBufferPool.Release(cmd);
        }

        public void SetValue(RenderTargetIdentifier source, Material material, string cameraName)
        {
            this.material = material; //接受面板材质
            this.source = source;
            this.cameraName = cameraName;
        }
    }
}

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PostGammaToLinner Shader

使用Amplify 连一个，其中_MainTex是必须的