Documentation pass on Custom Post Process supporting DRS / DLSS

com.unity.render-pipelines.high-definition/Documentation~/Custom-Post-Process.md

@@ -289,6 +289,20 @@ sealed class GrayScaleEditor : VolumeComponentEditor
 ```
 This custom editor is not really useful as it produces the same result as the editor that Unity creates. Custom Volume component editors also support an [additonal properties toggle](More-Options.md). To add it, you have to set hasAdvancedMode override to true. Then, inside the OnInspectorGUI, you can use the isInAdvancedMode boolean to display more properties.
 
+## Dynamic resolution and DLSS support
+
+If you want to use DLSS and/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:
+
+```glsl
+#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 does not display correctly:
@@ -301,6 +315,8 @@ If your effect does not display correctly:
 
 * Check that your shader doesn't contain any **clip()** instructions, that the blend mode is set to Off and the output alpha is always 1.
 
+* If your effect does not work with dynamic resolution, use the _PostProcessScreenSize constant to make it fit the size of the screen correctly. You only need to do this when you use dynamic resolution scaling (DRS), and you need normal / 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 to not be rendered anymore.

com.unity.render-pipelines.high-definition/Editor/PostProcessing/Templates/CustomPostProcessingShader.template

@@ -48,7 +48,7 @@ Shader "Hidden/Shader/#SCRIPTNAME#"
     {
         UNITY_SETUP_STEREO_EYE_INDEX_POST_VERTEX(input);
 
-        // Note that if HDUtils.DrawFullScreen is used to render the post process, input.texcoord needs to be multiplied by _RTHandleScale.xy
+        // Note that if HDUtils.DrawFullScreen is used to render the post process, use ClampAndScaleUVForBilinearPostProcessTexture(input.texcoord.xy) to get the correct UVs
 
         float3 sourceColor = SAMPLE_TEXTURE2D_X(_MainTex, s_linear_clamp_sampler, input.texcoord).xyz;