Custom post-processing

The High Definition Render Pipeline (HDRP) allows you to write your own post-processing effects that automatically integrate into Volumes.

Create a custom post-processing effect

A custom post-processing effect requires the following files:

• A C# Custom Post Process Volume.
• An associated full-screen shader. You can use a shader file or a Fullscreen Shader Graph.

HDRP includes a template of each file you need to set up custom post-processing. To generate each template:

• C# Custom Post Process Volume: Go to Assets > Create > Rendering and select HDRP C# Post Process Volume.

• Full-screen shader:

  • To create a shader file, go to Assets > Create > Shader and select HDRP Post Process.
  • To create a Fullscreen Shader Graph, go to Assets > Create > Shader Graph > HDRP and select Fullscreen Shader Graph.

This creates each template file in the Project window in the Assets folder.

Apply a custom post-processing effect

For HDRP to recognize a custom post-processing effect in your project, assign it in the Global Settings:

1. Go to Edit > Project Settings > Graphics and select the HDRP Global Settings tab.
2. Scroll down until you find the Custom Post Process Orders section. This section contains a list for each injection point.
3. In the After Post Process field, select Add (+).
4. Select the name of the custom post-processing you want to apply.

This also allows you to control the execution order of the post-processing effects in your scene. For more information, see Order custom post-processing effects.

To apply a custom post-processing effect in your scene, set up a volume component:

1. Create a Volume component (Menu: GameObject > Volume).
2. Select the Volume in the Hierarchy menu.
3. In the Profile field, select the volume profile picker (circle) to add an existing volume profile, or select New to create a new volume profile.
4. In the Inspector, select Add Override.
5. In the dropdown, search for the name of the Custom Post Process Volume script and select it.

For a full script example you can use, see Custom post-processing example scripts.

Order custom post-processing effects

HDRP allows you to customize the order of your custom post-processing effects at each stage in the rendering process. These stages are called injection points.

To determine the injection points in which your effect can appear, change the enum in the following line in the C# Custom Post Process Volume:

public override CustomPostProcessInjectionPoint injectionPoint => CustomPostProcessInjectionPoint.AfterPostProcess;

For more information on which enums you can use, see CustomPostProcessInjectionPoint.

To order your custom post-processing effects:

1. Go to Edit > Project Settings > Graphics and select the HDRP Global Settings tab.
2. Scroll down until you find the Custom Post Process Orders section. This section contains a field for each injection point.
3. Select the Add (+) icon to add an effect to an injection point field.

To change the order HDRP executes multiple post-processing effects within an injection point, move them up or down in this list. HDRP executes the effects in order from top to bottom.

Set the full-screen shader in the post-processing script

You can use HDRP’s Fullscreen Master Stack to create a full-screen shader that you can use in a custom post-processing effect. This means you don’t need to write any shader code.

To use a full-screen shader with a custom post-processing volume:

1. In the Project window, select the full-screen shader graph to view it in the Inspector.
2. Find the name and subcategory of the fullscreen shader. For example ShaderGraphs/Fullscreen_PostProcess
3. In the Project window, double-click the custom post-processing volume script to open it in a script editor.
4. In the custom post-processing volume script, find the following line that defines the name and subcategory of the shader the volume uses:

 const string kShaderName = "Hidden/Shader/NewPostProcessVolume";

5. Replace Hidden/Shader/NewPostProcessVolume with the name and subcategory of the fullscreen shader you want to use in this custom post-processing effect. For example:

const string kShaderName = "ShaderGraphs/Fullscreen_PostProcess";

Custom post-processing example scripts

This example shows you how to create a grayscale effect. To get started:

1. Create a C# Custom Post Process file (right click in the Assets folder: Create > Rendering > HDRP C# Post Process Volume) and call it GrayScale. Note: Because of how serialization works in Unity, the file name and the class name must be identical or Unity doesn't serialize it correctly.

2. Copy the example code from the GrayScale C# script section into your C# Post Process Volume.

3. Create a full screen post-process Shader (right click in the Assets folder: Create > Shader > HDRP > Post Process) and call it GrayScale.

4. Copy the example code from the GrayScale Shader section into your post-process Shader.

5. Add the GrayScale effect to the list of custom post-processes that your Project executes. To do this, go to Edit > Project Settings > HDRP Default Settings and, at the bottom of the After Post Process list, click on the + and select GrayScale.

6. Now you can add the GrayScale post-process override to Volumes in the Scene. To change the effect settings, click the small all text just below the foldout arrow and adjust with the Intensity slider.

7. Optionally, you can create a custom editor for your post-processing effect. For information on how to do this, see custom editor.

GrayScale C# script

This is the C# Custom Post Process file. Custom post-process effects store both configuration data and logic in the same class. To create the settings for the effect, you can either use a pre-existing class that inherits from VolumeParameter, or, if you want to use a property that the pre-existing classes don't include, create a new class that inherits from VolumeParameter.

using UnityEngine;
using UnityEngine.Rendering;
using UnityEngine.Rendering.HighDefinition;
using System;

[Serializable, VolumeComponentMenu("Post-processing/Custom/GrayScale")]
public sealed class GrayScale : CustomPostProcessVolumeComponent, IPostProcessComponent
{
    [Tooltip("Controls the intensity of the effect.")]
    public ClampedFloatParameter intensity = new ClampedFloatParameter(0f, 0f, 1f);

    Material m_Material;

    public bool IsActive() => m_Material != null && intensity.value > 0f;

    public override CustomPostProcessInjectionPoint injectionPoint => CustomPostProcessInjectionPoint.AfterPostProcess;

    public override void Setup()
    {
        if (Shader.Find("Hidden/Shader/GrayScale") != null)
            m_Material = new Material(Shader.Find("Hidden/Shader/GrayScale"));
    }

    public override void Render(CommandBuffer cmd, HDCamera camera, RTHandle source, RTHandle destination)
    {
        if (m_Material == null)
            return;

        m_Material.SetFloat("_Intensity", intensity.value);
        cmd.Blit(source, destination, m_Material, 0);
    }

    public override void Cleanup() => CoreUtils.Destroy(m_Material);

}

This example code uses a ClampedFloatParameter that you can clamp to a range. In the constructor:

• The first parameter is the default value of the property.

• The second parameter represents the minimum value to clamp the property to.

• The third parameter represents the maximum value to clamp the property to.

HDRP calls the IsActive() function before the Render function to process the effect. If this function returns false, HDRP doesn't process the effect. It's good practice to check every property configuration where the effect either breaks or doesn'thing. In this example, IsActive() makes sure that HDRP can find the GrayScale.shader and that the intensity is greater than 0.

The injectionPoint override allows you to specify where in the pipeline HDRP executes the effect. Choose from the following injection points:

• AfterOpaqueAndSky

• BeforeTAA

• BeforePostProcess

• AfterPostProcessBlurs.

• AfterPostProcess.

The following diagram gives more information on where HDRP injects custom post-process passes:

Note: When you enable Temporal antialiasing (TAA), HDRP applies TAA between the injection points BeforeTAA and beforePostProcess. When you use Depth Of Field and enable its Physically Based property, HDRP performs a second TAA pass to perform temporal accumulation for this effect.

The Setup, Render, and Cleanup functions allocate, use, and release the resources that the effect needs. The only resource that the above script example uses is a single Material. This example creates the Material in Setup and, in Cleanup, uses CoreUtils.Destroy() to release the Material.

In the Render function, you have access to a CommandBuffer which you can use to enqueue tasks for HDRP to execute. You can use CommandBuffer.Blit here to render a fullscreen quad. When you use the Blit function, Unity binds the source buffer in parameter to the _MainTex property in the shader. For this to happen, you need to declare the _MainTex property in the Properties section of the shader.

Note: You can also use the HDUtils.DrawFullscreen method. To do this, you need to multiply the input.texcoord by the _RTHandleScale.xy property to account for dynamic scaling.

GrayScale Shader

HDRP gives you total control over the vertex and fragment Shader so you can edit both of them to suit your needs.

There are several utility functions in Common.hlsl and Color.hlsl that the Shader includes by default. This means that you have access to these utility functions in your effect. For example, the GrayScale Shader uses the Luminance() function to convert a linear RGB value to its luminance equivalent.

Shader "Hidden/Shader/GrayScale"
{
    Properties
    {
        // This property is necessary to make the CommandBuffer.Blit bind the source texture to _MainTex
        _MainTex("Main Texture", 2DArray) = "grey" {}
    }

    HLSLINCLUDE

    #pragma target 4.5
    #pragma only_renderers d3d11 playstation xboxone xboxseries vulkan metal switch

    #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Common.hlsl"
    #include "Packages/com.unity.render-pipelines.core/ShaderLibrary/Color.hlsl"
    #include "Packages/com.unity.render-pipelines.high-definition/Runtime/ShaderLibrary/ShaderVariables.hlsl"
    #include "Packages/com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/FXAA.hlsl"
    #include "Packages/com.unity.render-pipelines.high-definition/Runtime/PostProcessing/Shaders/RTUpscale.hlsl"

    struct Attributes
    {
        uint vertexID : SV_VertexID;
        UNITY_VERTEX_INPUT_INSTANCE_ID
    };

    struct Varyings
    {
        float4 positionCS : SV_POSITION;
        float2 texcoord   : TEXCOORD0;
        UNITY_VERTEX_OUTPUT_STEREO

    };

    Varyings Vert(Attributes input)
    {
        Varyings output;

        UNITY_SETUP_INSTANCE_ID(input);
        UNITY_INITIALIZE_VERTEX_OUTPUT_STEREO(output);

        output.positionCS = GetFullScreenTriangleVertexPosition(input.vertexID);
        output.texcoord = GetFullScreenTriangleTexCoord(input.vertexID);

        return output;
    }

    // List of properties to control your post process effect
    float _Intensity;
    TEXTURE2D_X(_MainTex);

    float4 CustomPostProcess(Varyings input) : SV_Target
    {
        UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);

        float3 sourceColor = SAMPLE_TEXTURE2D_X(_MainTex, s_linear_clamp_sampler, input.texcoord).xyz;

        // Apply greyscale effect
        float3 color = lerp(sourceColor, Luminance(sourceColor), _Intensity);

        return float4(color, 1);
    }

    ENDHLSL

    SubShader
    {
        Pass
        {
            Name "GrayScale"

            ZWrite Off
            ZTest Always
            Blend Off
            Cull Off

            HLSLPROGRAM
                #pragma fragment CustomPostProcess
                #pragma vertex Vert
            ENDHLSL
        }
    }

    Fallback Off
}

If none of your Scenes reference the Shader, Unity doesn't build the Shader and the effect doesn't work when you run your application outside of the Editor. To resolve this, do one of the following:

• Add the Shader to a Resources folder
• Go to Edit > Project Settings > Graphics and add the Shader to the Always Included Shaders list.

Note: When HDRP executes your post-process effect, it uses a render target pooling system. It means that you don't know what the current color buffer contains, which is why you should never use any instructions that could display this color buffer. don't use transparency, blend modes, or the clip() instruction in your Shader, otherwise your effect breaks.

Shader inputs

By default, the Shader template provides you with the following inputs:

Input	description
positionCS	The clip space position of the pixel. This value is between 0 and the current screen size.
texcoord	The full screen UV coordinate. This value is between 0 and 1.
_InputTexture	The source Texture. The GrayScale C# script passes this to the Shader.
_Intensity	The intensity of the effect. The GrayScale C# script passes this to the Shader.

Custom editor

By default, Unity automatically creates an editor for classes but, if you want more control over how Unity displays certain properties, you can create a custom editor. If you do create a custom editor script, make sure to put it in a folder named Editor.

The following is an example of a custom editor for the GrayScale effect:

using UnityEditor.Rendering;
using UnityEngine;
using UnityEngine.Rendering.HighDefinition;
using UnityEditor;

[CustomEditor(typeof(GrayScale))]
sealed class GrayScaleEditor : VolumeComponentEditor
{
    SerializedDataParameter m_Intensity;

    public override void OnEnable()
    {
        base.OnEnable();
        var o = new PropertyFetcher<GrayScale>(serializedObject);
        m_Intensity = Unpack(o.Find(x => x.intensity));
    }

    public override void OnInspectorGUI()
    {
        PropertyField(m_Intensity);
    }
}

This custom editor isn't useful as it produces the same result as the editor that Unity creates. Custom Volume component editors also support an additonal properties toggle. To add it, you have to set the hasAdvancedMode override to true. Then, inside OnInspectorGUI, you can use the isInAdvancedMode Boolean to display more properties.

Dynamic resolution and DLSS support

If you want to use DLSS or dynamic resolution on your pass, and you need to interpolate or sample UVs from color, normal, or velocity, you must use the following functions to calculate the correct UVs:

#include "Packages/com.unity.render-pipelines.high-dynamic/Runtime/ShaderLibrary/ShaderVariables.hlsl"

//...

float2 UVs = ... //the uvs coming from the interpolator
float2 correctUvs = ClampAndScaleUVForBilinearPostProcessTexture(UV); // use these uvs to sample color / normal and velocity

Troubleshooting

If your effect doesn't display correctly:

• In your Project Settings, make sure this effect is listed under one of the post process order lists (see Effect Ordering).

• Check that your effect's Shader compiles and that the reference to the Material in your post process Volume isn't null.

• In the Volume that contains your post process, make sure that it has a high enough priority and that your Camera is inside its bounds.

• Check that your shader doesn't contain any clip() instructions, that the blend mode is Off and the output alpha has a value of 1.

• If your effect doesn't work with dynamic resolution, use the _PostProcessScreenSize constant to make it fit the size of the screen. You only need to do this when you also need normal or velocity and color.

Known issues and limitations

• Renaming a custom post process class name and file will remove it from the list in HDRP Project Settings causing the effect not to be rendered anymore.