[URP RenderGraph] Sample code fixes

Only URP package doc and sample scene script changes. No engine code changes.
- Fixes GC.Alloc that happens every frame in URP package doc and package sample scene script [slack](https://unity.slack.com/archives/C010YL29H8F/p1718105805466559)
- Blur sample do not use frame buffer fetch. Just use normal blit [UUM-74051](https://jira.unity3d.com/browse/UUM-74051)

Author: cinight

Packages/com.unity.render-pipelines.universal/Documentation~/renderer-features/create-custom-renderer-feature.md

@@ -311,10 +311,7 @@ This section demonstrates how to implement the settings for the custom blur rend
 
         // Blit from the camera color to the render graph texture,
         // using the first shader pass.
-        builder.SetRenderFunc((PassData data, RasterGraphContext context) =>
-        {
-            Blitter.BlitTexture(context.cmd, data.src, m_ScaleBias, data.material, 0);
-        });
+        builder.SetRenderFunc((PassData data, RasterGraphContext context) => ExecutePass(data, context, 0));
     }
     ```
 
@@ -324,33 +321,25 @@ This section demonstrates how to implement the settings for the custom blur rend
     private Vector4 m_ScaleBias = new Vector4(1f, 1f, 0f, 0f);
     ```
 
-2. In the `RecordRenderGraph` method, using the `builder` variable, add the render pass for the horizontal blur. This pass uses the output of the previous pass as its input, it does that using the `FrameBufferFetch` method. In this example, using this method lets URP merge two blur passes into a single render pass. Refer to the complete shader code for the implementation details.
+2. In the `RecordRenderGraph` method, using the `builder` variable, add the render pass for the horizontal blur. This pass uses the output of the previous pass as its input. Refer to the complete shader code for the implementation details.
 
     ```C#
     // Horizontal blur pass
-    using (var builder = renderGraph.AddRasterRenderPass<PassData>(k_HorizontalPassName,
-            out var passData))
+    using (var builder = renderGraph.AddRasterRenderPass<PassData>(k_HorizontalPassName, out var passData))
     {
-        // Reset unused passData fields
-        passData.src = TextureHandle.nullHandle;
-
-        // Use the same material as the previous pass
+        // Configure pass data
+        passData.src = dst;
         passData.material = material;
 
-        // Use the output of the previous pass as the input,
-        // and bind it as FrameBufferFetch input
-        builder.SetInputAttachment(dst, 0);
-
+        // Use the output of the previous pass as the input
+        builder.UseTexture(passData.src);
+        
         // Use the input texture of the previous pass as the output
         builder.SetRenderAttachment(srcCamColor, 0);
 
         // Blit from the render graph texture to the camera color,
-        // using the second shader pass,
-        // which reads the input texture using the FrameBufferFetch method.
-        builder.SetRenderFunc((PassData data, RasterGraphContext context) =>
-        {
-            Blitter.BlitTexture(context.cmd, m_ScaleBias, data.material, 1);
-        });
+        // using the second shader pass.
+        builder.SetRenderFunc((PassData data, RasterGraphContext context) => ExecutePass(data, context, 1));
     }
     ```
 
@@ -513,7 +502,7 @@ public class BlurRendererFeature : ScriptableRendererFeature
         material = new Material(shader);
         blurRenderPass = new BlurRenderPass(material, settings);
 
-        blurRenderPass.renderPassEvent = RenderPassEvent.AfterRenderingSkybox;
+        blurRenderPass.renderPassEvent = RenderPassEvent.BeforeRenderingPostProcessing;
     }
 
     public override void AddRenderPasses(ScriptableRenderer renderer,
@@ -569,7 +558,7 @@ public class BlurRenderPass : ScriptableRenderPass
     private const string k_VerticalPassName = "VerticalBlurRenderPass";
     private const string k_HorizontalPassName = "HorizontalBlurRenderPass";
 
-    private Vector4 m_ScaleBias = new Vector4(1f, 1f, 0f, 0f);
+    private static Vector4 m_ScaleBias = new Vector4(1f, 1f, 0f, 0f);
 
     private BlurSettings defaultSettings;
     private Material material;
@@ -606,6 +595,11 @@ public class BlurRenderPass : ScriptableRenderPass
         internal Material material;
     }
 
+    private static void ExecutePass(PassData data, RasterGraphContext context, int pass)
+    {
+        Blitter.BlitTexture(context.cmd, data.src, m_ScaleBias, data.material, pass);
+    }
+
     public override void RecordRenderGraph(RenderGraph renderGraph,
     ContextContainer frameData)
     {
@@ -648,36 +642,25 @@ public class BlurRenderPass : ScriptableRenderPass
 
             // Blit from the camera color to the render graph texture,
             // using the first shader pass.
-            builder.SetRenderFunc((PassData data, RasterGraphContext context) =>
-            {
-                Blitter.BlitTexture(context.cmd, data.src, m_ScaleBias, data.material, 0);
-            });
+            builder.SetRenderFunc((PassData data, RasterGraphContext context) => ExecutePass(data, context, 0));
         }
-
+        
         // Horizontal blur pass
-        using (var builder = renderGraph.AddRasterRenderPass<PassData>(k_HorizontalPassName,
-            out var passData))
+        using (var builder = renderGraph.AddRasterRenderPass<PassData>(k_HorizontalPassName, out var passData))
         {
-            // Reset unused passData fields
-            passData.src = TextureHandle.nullHandle;
-
-            // Use the same material as the previous pass
+            // Configure pass data
+            passData.src = dst;
             passData.material = material;
 
-            // Use the output of the previous pass as the input,
-            // and bind it as FrameBufferFetch input
-            builder.SetInputAttachment(dst, 0);
-
+            // Use the output of the previous pass as the input
+            builder.UseTexture(passData.src);
+            
             // Use the input texture of the previous pass as the output
             builder.SetRenderAttachment(srcCamColor, 0);
 
             // Blit from the render graph texture to the camera color,
-            // using the second shader pass,
-            // which reads the input texture using the FrameBufferFetch method.
-            builder.SetRenderFunc((PassData data, RasterGraphContext context) =>
-            {
-                Blitter.BlitTexture(context.cmd, m_ScaleBias, data.material, 1);
-            });
+            // using the second shader pass.
+            builder.SetRenderFunc((PassData data, RasterGraphContext context) => ExecutePass(data, context, 1));
         }
     }
 }
@@ -735,6 +718,23 @@ Shader "CustomEffects/Blur"
             
             return float4(color.rgb / (BLUR_SAMPLES + 1), 1);
         }
+
+        float4 BlurHorizontal (Varyings input) : SV_Target
+        {
+            const float BLUR_SAMPLES = 64;
+            const float BLUR_SAMPLES_RANGE = BLUR_SAMPLES / 2;
+            
+            UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
+            float3 color = 0;
+            float blurPixels = _HorizontalBlur * _ScreenParams.x;
+            for(float i = -BLUR_SAMPLES_RANGE; i <= BLUR_SAMPLES_RANGE; i++)
+            {
+                float2 sampleOffset =
+                    float2 ((blurPixels / _BlitTexture_TexelSize.z) * (i / BLUR_SAMPLES_RANGE), 0);
+                color += SAMPLE_TEXTURE2D(_BlitTexture, sampler_LinearClamp, input.texcoord + sampleOffset).rgb;
+            }
+            return float4(color / (BLUR_SAMPLES + 1), 1);
+        }
 
     ENDHLSL
 
@@ -757,30 +757,12 @@ Shader "CustomEffects/Blur"
         
         Pass
         {
-            Name "BlurPassHorizontal_FrameBufferFetch"
+            Name "BlurPassHorizontal"
 
             HLSLPROGRAM
             
             #pragma vertex Vert
-            #pragma fragment Frag
-
-           FRAMEBUFFER_INPUT_X_HALF(0);
-
-           float4 Frag(Varyings input) : SV_Target
-           {
-                const float BLUR_SAMPLES = 64;
-                const float BLUR_SAMPLES_RANGE = BLUR_SAMPLES / 2;
-                
-                UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
-                float3 color = 0;
-                float blurPixels = _HorizontalBlur * _ScreenParams.x;
-                for(float i = -BLUR_SAMPLES_RANGE; i <= BLUR_SAMPLES_RANGE; i++)
-                {
-                    float2 sampleOffset = float2 ((blurPixels / 1) * (i / BLUR_SAMPLES_RANGE), 0);
-                    color += LOAD_FRAMEBUFFER_X_INPUT(0, input.positionCS.xy + sampleOffset).rgb;
-                }
-                return float4(color / (BLUR_SAMPLES + 1), 1);
-           }
+            #pragma fragment BlurHorizontal
             
             ENDHLSL
         }

Packages/com.unity.render-pipelines.universal/Samples~/URPPackageSamples/RendererFeatures/BlitToRTHandle/BlitToRTHandlePass.cs

@@ -11,10 +11,9 @@ class PassData
     {
         public TextureHandle source;
         public Material material;
-        public Vector4 scaleBias;
     }
 
-    private Vector4 m_ScaleBias = new Vector4(1f, 1f, 0f, 0f);
+    private static Vector4 m_ScaleBias = new Vector4(1f, 1f, 0f, 0f);
     private ProfilingSampler m_ProfilingSampler = new ProfilingSampler("BlitToRTHandle_CopyColor");
     private RTHandle m_InputHandle;
     private RTHandle m_OutputHandle;
@@ -93,15 +92,14 @@ public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer
 
             passData.source = source;
             passData.material = m_Material;
-            passData.scaleBias = m_ScaleBias;
             builder.UseTexture(source, AccessFlags.Read); // Set the camera color as the input
             builder.SetRenderAttachment(destination, 0, AccessFlags.Write); // Set the target texture
             builder.SetGlobalTextureAfterPass(destination, m_OutputId); // Make the output texture available for the shaders in the scene
 
             builder.SetRenderFunc((PassData data, RasterGraphContext context) =>
             {
                 // Blit the input texture to the destination target specified in the SetRenderAttachment method
-                Blitter.BlitTexture(context.cmd, data.source, data.scaleBias, data.material, 0);
+                Blitter.BlitTexture(context.cmd, data.source, m_ScaleBias, data.material, 0);
             });
         }
 

Packages/com.unity.render-pipelines.universal/Samples~/URPPackageSamples/RendererFeatures/DepthBlit/DepthBlitCopyDepthPass.cs

@@ -24,6 +24,10 @@ class PassData
         public TextureHandle source;
         public Vector4 scaleBias;
         public int depthBufferId;
+        public GlobalKeyword keyword_DepthMsaa2;
+        public GlobalKeyword keyword_DepthMsaa4;
+        public GlobalKeyword keyword_DepthMsaa8;
+        public GlobalKeyword keyword_OutputDepth;
     }
 
     public DepthBlitCopyDepthPass(RenderPassEvent evt, Shader copyDepthShader, RTHandle destination)
@@ -103,6 +107,10 @@ public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer
             passData.source = src;
             passData.scaleBias = m_ScaleBias;
             passData.depthBufferId = m_DepthBufferId;
+            passData.keyword_DepthMsaa2 = m_Keyword_DepthMsaa2;
+            passData.keyword_DepthMsaa4 = m_Keyword_DepthMsaa4;
+            passData.keyword_DepthMsaa8 = m_Keyword_DepthMsaa8;
+            passData.keyword_OutputDepth = m_Keyword_OutputDepth;
 
             builder.UseTexture(src, AccessFlags.Read);
             builder.SetRenderAttachment(dest, 0, AccessFlags.Write);
@@ -114,12 +122,12 @@ public override void RecordRenderGraph(RenderGraph renderGraph, ContextContainer
                 // Enable an MSAA shader keyword based on the source texture MSAA sample count
                 RTHandle sourceTex = data.source;
                 int cameraSamples = sourceTex.rt.antiAliasing;
-                context.cmd.SetKeyword(m_Keyword_DepthMsaa2, cameraSamples == 2);
-                context.cmd.SetKeyword(m_Keyword_DepthMsaa4, cameraSamples == 4);
-                context.cmd.SetKeyword(m_Keyword_DepthMsaa8, cameraSamples == 8);
+                context.cmd.SetKeyword(data.keyword_DepthMsaa2, cameraSamples == 2);
+                context.cmd.SetKeyword(data.keyword_DepthMsaa4, cameraSamples == 4);
+                context.cmd.SetKeyword(data.keyword_DepthMsaa8, cameraSamples == 8);
 
                 // This example does not copy the depth values back to the depth buffer, so we disable this keyword.
-                context.cmd.SetKeyword(m_Keyword_OutputDepth, false);
+                context.cmd.SetKeyword(data.keyword_OutputDepth, false);
 
                 // Bind the depth buffer to the material
                 data.copyDepthMaterial.SetTexture(data.depthBufferId, data.source);