[Port] [2022.3] DOCG-6491 Custom render passes and volumes documentation

Author: markg-unity

Packages/com.unity.render-pipelines.universal/Documentation~/TableOfContents.md

@@ -143,7 +143,8 @@
     * [Scriptable Render Passes](renderer-features/scriptable-render-passes.md)
       * [Scriptable Render Passes](renderer-features/intro-to-scriptable-render-passes.md)
       * [Write a Scriptable Render Pass](renderer-features/write-a-scriptable-render-pass.md)
-      * [Inject a pass via scripting](customize/inject-render-pass-via-script.md)    
+      * [Inject a pass via scripting](customize/inject-render-pass-via-script.md)  
+      * [Restrict a render pass to a scene area](customize/restrict-render-pass-scene-area.md)        
     * [Scriptable Renderer Features](renderer-features/scriptable-renderer-features/scriptable-renderer-features-landing.md)
       * [Introduction to Scriptable Renderer Features](renderer-features/scriptable-renderer-features/intro-to-scriptable-renderer-features.md)
       * [Inject a custom render pass using a Scriptable Renderer Feature](renderer-features/scriptable-renderer-features/inject-a-pass-using-a-scriptable-renderer-feature.md)

Packages/com.unity.render-pipelines.universal/Documentation~/customize/restrict-render-pass-scene-area.md

@@ -0,0 +1,112 @@
+# Restrict a render pass to a scene area in URP
+
+To restrict a render pass to a specific area of a scene, add a [volume](../Volumes.md) to the scene, then add code to your render pass and your shader to check if the camera is inside the volume.
+
+Follow these steps:
+
+1. Update your shader code to enable or disable your custom rendering effect based on a Boolean value.
+
+    For example, add the following code to your shader:
+
+    ```hlsl
+    Pass
+    {
+        ...
+
+        // Add a variable to enable or disable your custom rendering effect
+        float _Enabled;
+
+        ...
+
+        float4 Frag(Varyings input) : SV_Target0
+        {
+            ...
+
+            // Return the color with the effect if the variable is 1, or the original color if the variable is 0
+            if (_Enabled == 1){
+                return colorWithEffect;
+            } else {
+                return originalColor;
+            }
+        }
+    }
+    ```
+
+2. Create a script that implements the `VolumeComponent` class. This creates a volume override component that you can add to a volume.
+
+    ```c#
+    using UnityEngine;
+    using UnityEngine.Rendering;
+
+    public class MyVolumeOverride : VolumeComponent
+    {
+    }
+    ```
+
+3. In the **Hierarchy** window, select the **Add** (**+**) button, then select **GameObject** > **Volume** > **Box Volume**.
+
+4. In the **Inspector** window for the new box volume, under **Volume**, select **New** to create a new volume profile.
+
+5. Select **Add override**, then select your volume override component, for example **My Volume Override**.
+
+6. Add a property to the volume override script. Unity adds the property in the **Inspector** window of the volume override.
+
+    For example:
+
+    ```c#
+    public class MyVolumeOverride : VolumeComponent
+    {
+        // Add an 'Effect Enabled' checkbox to the Volume Override, with a default value of true.
+        public BoolParameter effectEnabled = new BoolParameter(true);
+    }
+    ```
+
+5. In your custom pass, use the `GetComponent` API to get the volume override component and check the value of the property.
+
+    For example:
+
+    ```c#
+    class myCustomPass : ScriptableRenderPass
+    {
+
+        ...
+
+        public void Setup(Material material)
+        {
+            // Get the volume override component
+            MyVolumeOverride myOverride = VolumeManager.instance.stack.GetComponent<MyVolumeOverride>();
+
+            // Get the value of the 'Effect Enabled' property
+            bool effectStatus = myOverride.effectEnabled.overrideState ? myOverride.effectEnabled.value : false;
+        }
+    }
+    ```
+
+6. Pass the value of the property to the variable you added to the shader code.
+
+    For example:
+
+    ```c#
+    class myCustomPass : ScriptableRenderPass
+    {
+
+        ...
+
+        public void Setup(Material material)
+        {
+            MyVolumeOverride myOverride = VolumeManager.instance.stack.GetComponent<MyVolumeOverride>();
+            bool effectStatus = myOverride.effectEnabled.overrideState ? myOverride.effectEnabled.value : false;
+
+            // Pass the value to the shader
+            material.SetFloat("_Enabled", effectStatus ? 1 : 0);
+        }
+    }
+    ```
+
+Your custom rendering effect is now enabled when the camera is inside the volume, and disabled when the camera is outside the volume.
+
+## Additional resources
+
+- [Write a Scriptable Render Pass](../renderer-features/write-a-scriptable-render-pass.md)
+- [Volumes in URP](../volumes.md)
+- [Writing custom shaders in URP](../writing-custom-shaders-urp.md)

Packages/com.unity.render-pipelines.universal/Documentation~/renderer-features/scriptable-render-passes.md

@@ -7,6 +7,7 @@ Use the `ScriptableRenderPass` API to write a custom render pass. You can then i
 |[Introduction to Scriptable Render Passes](intro-to-scriptable-render-passes.md)|What a Scriptable Render Pass is, and how you can inject it into a scene.|
 |[Write a Scriptable Render Pass](write-a-scriptable-render-pass.md)|An example of a `ScriptableRenderPass` instance that uses `Blit` to create a red tint effect.|
 |[Inject a pass via scripting](../customize/inject-render-pass-via-script.md)|Use the `RenderPipelineManager` API to inject a render pass, without using a Scriptable Renderer Feature.|
+|[Restrict a render pass to a scene area](../customize/restrict-render-pass-scene-area.md) | Enable a custom rendering effect only if the camera is inside a volume in a scene. |
 
 ## Additional resources