Drive parallax height and relief from the painted occlusion channel

Reuse the existing occlusion paint channel (no new map, MAP_COUNT stays 3):
0.5 is neutral, above 0.5 raises a hill, below 0.5 sinks a hole and also
fades ambient occlusion (saturate(2*occ)). Bind the MSO map to _ParallaxMap,
enable _PARALLAXMAP, derive a relief normal from the height gradient, and
reseed unpainted occlusion to 0.5 so untouched surfaces stay visually neutral.
Pin the _PARALLAXMAP runtime variant in the build keep-alive material.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Assets/Scripts/MeshPainter.Backend.cs

@@ -69,8 +69,9 @@ public partial class MeshPainter
         switch (mi)
         {
             case MAP_ALBEDO: return new[] { "_BaseMap", "_MainTex" };
-            // One mask map drives both URP slots: _MetallicGlossMap (R/A) + _OcclusionMap (G).
-            case MAP_MSO: return new[] { "_MetallicGlossMap", "_OcclusionMap" };
+            // One mask map drives three URP slots: _MetallicGlossMap (R/A) + _OcclusionMap (G) +
+            // _ParallaxMap (G = occlusion reused as a 0.5-centred height for parallax/relief).
+            case MAP_MSO: return new[] { "_MetallicGlossMap", "_OcclusionMap", "_ParallaxMap" };
             default: return new[] { "_EmissionMap" };
         }
     }

Assets/Scripts/MeshPainter.Setup.cs

@@ -148,12 +148,14 @@ public partial class MeshPainter
         _seedCanonical = new Color32[MAP_COUNT][];
         _seedCanonical[MAP_ALBEDO] = BuildBaseColors();
 
-        // Mask map seed from the material scalars: R = metallic, G = occlusion (255 =
-        // unoccluded, so the look is unchanged until painted), B = 0, A = smoothness.
+        // Mask map seed from the material scalars: R = metallic, G = occlusion/height, B = 0,
+        // A = smoothness. G = 128 (= 0.5) is the NEUTRAL height: no parallax/relief and AO =
+        // saturate(2*0.5) = 1 (no darkening), so the unpainted look is unchanged. Painting G
+        // below 0.5 carves a hole (and darkens), above 0.5 raises a hill (see PlayerCamoLit).
         float metallic0 = _materialInstance.HasProperty(MetallicId) ? _materialInstance.GetFloat(MetallicId) : 0f;
         float smoothness0 = _materialInstance.HasProperty(SmoothnessId) ? _materialInstance.GetFloat(SmoothnessId) : 0.5f;
         _seedCanonical[MAP_MSO] = FillCanonical(new Color32(
-            (byte)(Mathf.Clamp01(metallic0) * 255f), 255, 0, (byte)(Mathf.Clamp01(smoothness0) * 255f)));
+            (byte)(Mathf.Clamp01(metallic0) * 255f), 128, 0, (byte)(Mathf.Clamp01(smoothness0) * 255f)));
 
         // Emission: keep the existing look (black if the material's emission is off).
         Color emission0 = Color.black;
@@ -232,6 +234,18 @@ public partial class MeshPainter
             _materialInstance.EnableKeyword("_OCCLUSIONMAP");
             if (_materialInstance.HasProperty(OcclusionStrengthId)) _materialInstance.SetFloat(OcclusionStrengthId, 1f);
         }
+
+        // Height: the same mask map is also bound to _ParallaxMap (see MapProps), so the painted
+        // occlusion value (G) doubles as a 0.5-centred height. _PARALLAXMAP turns on URP's single-
+        // step parallax (ApplyPerPixelDisplacement) AND our relief-normal/AO remap in PlayerCamoLit.
+        // Lift _Parallax off its floor so the displacement is actually visible (the relief normal is
+        // the dominant cue; this just adds subtle motion parallax). Live-tunable on the instance.
+        if (_materialInstance.HasProperty(ParallaxMapId))
+        {
+            _materialInstance.EnableKeyword("_PARALLAXMAP");
+            if (_materialInstance.HasProperty(ParallaxId) && _materialInstance.GetFloat(ParallaxId) < 0.02f)
+                _materialInstance.SetFloat(ParallaxId, 0.02f);
+        }
     }
 
     /// <summary>Pushes the global emission intensity to the material's _EmissionColor (live-tunable).</summary>

Assets/Scripts/MeshPainter.cs

@@ -130,9 +130,10 @@ public partial class MeshPainter : MonoBehaviour
     [Range(0f, 1f)]
     public float metallicSmoothnessOpacity = 1f;
 
-    [Tooltip("Ambient occlusion painted into the mask map (1 = fully lit / no darkening, " +
-             "0 = fully occluded / dark). NOTE: URP only darkens INDIRECT light (ambient + " +
-             "reflections), so the effect is subtle under strong direct lighting. 1 = no-op.")]
+    [Tooltip("Occlusion + HEIGHT painted into the mask map (one value, 0..1, 0.5 = neutral/no-op). " +
+             "Drives parallax + a relief normal: 0.5 = flat, >0.5 = raised hill, <0.5 = carved hole. " +
+             "Also drives ambient occlusion, but only the LOWER half darkens: 0.5..1 = fully lit, " +
+             "0.5..0 = AO fades 1..0 (so a hole is also darker). See Custom/PlayerCamoLit.")]
     [Range(0f, 1f)]
     public float occlusion = 0.5f;
 
@@ -284,7 +285,7 @@ public partial class MeshPainter : MonoBehaviour
 
     // Seed colors per map in canonical (material) layout, built once at Start:
     //   albedo   -> RGB color
-    //   MSO      -> R = metallic, G = occlusion (1 = unoccluded), A = smoothness (mask map)
+    //   MSO      -> R = metallic, G = occlusion/height (0.5 = neutral: no relief, AO = 1), A = smoothness
     //   emission -> RGB emission
     private Color32[][] _seedCanonical;
 
@@ -322,6 +323,8 @@ public partial class MeshPainter : MonoBehaviour
     private static readonly int EmissionColorId = Shader.PropertyToID("_EmissionColor");
     private static readonly int OcclusionMapId = Shader.PropertyToID("_OcclusionMap");
     private static readonly int OcclusionStrengthId = Shader.PropertyToID("_OcclusionStrength");
+    private static readonly int ParallaxMapId = Shader.PropertyToID("_ParallaxMap");
+    private static readonly int ParallaxId = Shader.PropertyToID("_Parallax");
     private static readonly int HalfLambertId = Shader.PropertyToID("_HalfLambert");
     private static readonly int HalfLambertBrightnessId = Shader.PropertyToID("_HalfLambertBrightness");
     private static readonly int SpecularDampenId = Shader.PropertyToID("_SpecularDampen");