Add warning message inside the UI to prevent wrong mapping with Pixel displacement

ScriptableRenderPipeline/HDRenderPipeline/Material/LayeredLit/Editor/LayeredLitUI.cs

             public readonly GUIContent heightOffset = new GUIContent("Height Offset", "Offset applied to the height before layering.");
             public readonly GUIContent heightTransition = new GUIContent("Height Transition", "Size in world units of the smooth transition between layers.");
 
+            public readonly GUIContent perPixelDisplacementLayersWarning = new GUIContent("For pixel displacement to work correctly, all layers with a heightmap must use the same UV mapping");
+
             public readonly GUIContent materialReferencesText = new GUIContent("Material References");
 
             public StylesLayer()
             {
                 optionsChanged = true;
             }
+
+            // In case of pixel displacement and layered shader, all layers must used the same texture mapping for layer that have a heightmap
+            // (Else the algorithm will not work correctly)
+            if ((DisplacementMode)displacementMode.floatValue == DisplacementMode.Pixel)
+            {
+                float compareValue = -1.0f;
+                bool match = true;
+
+                if (material.GetTexture(kHeightMap + 0))
+                {
+                    compareValue = UVBase[0].floatValue;
+                }
+                if (material.GetTexture(kHeightMap + 1))
+                {
+                    if (compareValue == -1.0f)
+                        compareValue = UVBase[1].floatValue;
+                    else if (compareValue != UVBase[1].floatValue)
+                        match = false;
+                }
+                if (material.GetTexture(kHeightMap + 2))
+                {
+                    if (compareValue == -1.0f)
+                        compareValue = UVBase[2].floatValue;
+                    else if (compareValue != UVBase[2].floatValue)
+                        match = false;
+                }
+                if (material.GetTexture(kHeightMap + 3))
+                {
+                    if (compareValue == -1.0f)
+                        compareValue = UVBase[3].floatValue;
+                    else if (compareValue != UVBase[3].floatValue)
+                        match = false;
+                }
+
+                if (!match)
+                {
+                    EditorGUILayout.HelpBox(s_Styles.perPixelDisplacementLayersWarning.text, MessageType.Warning);
+                }
+            }
+
 
             bool layerChanged = DoLayersGUI(materialImporter);
             DoEmissiveGUI(material);

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Editor/LitUI.cs

             // Transparency absorption
             public static GUIContent transmittanceColorText = new GUIContent("Transmittance Color", "Absorption color (RGB)");
             public static GUIContent atDistanceText = new GUIContent("Transmittance Absorption Distance", "Absorption distance reference");
+
+            public static GUIContent perPixelDisplacementDetailsWarning = new GUIContent("For pixel displacement to work correctly, details and base map must use same UV mapping");
         }
 
         // Lit shader is not layered but some layered materials inherit from it. In order to share code we need LitUI to account for this.
             UVDetailsMappingMask[layerIndex].colorValue = new Color(X, Y, Z, W);
 
             m_MaterialEditor.TextureScaleOffsetProperty(detailMap[layerIndex]);
+            if ((DisplacementMode)displacementMode.floatValue == DisplacementMode.Pixel && (UVDetail[layerIndex].floatValue != UVBase[layerIndex].floatValue))
+            {
+                if (material.GetTexture(kDetailMap + layerIndex))
+                    EditorGUILayout.HelpBox(Styles.perPixelDisplacementDetailsWarning.text, MessageType.Warning);
+            }
             m_MaterialEditor.ShaderProperty(detailAlbedoScale[layerIndex], Styles.detailAlbedoScaleText);
             m_MaterialEditor.ShaderProperty(detailNormalScale[layerIndex], Styles.detailNormalScaleText);
             m_MaterialEditor.ShaderProperty(detailSmoothnessScale[layerIndex], Styles.detailSmoothnessScaleText);