Camo: generalize brightness + add persistent saturation

Move brightness out of the half-lambert diffuse term to a final exposure
multiply on the whole shaded body color (diffuse + GI + specular), and add
a saturation grade (0 = neutral, -1 = grayscale, >0 = boosted) on the same
final stage. Saturation rides as a 4th component on CamoKnobs (Vector3 ->
Vector4) so it inherits all three persistence paths: HUD JSON, network
replication (_camo NetworkVariable), and painting-slot metadata. Wires the
renamed Slider_Brightness and new Slider_Saturation. Bumps HudFileVersion
and PaintMetaVersion with load-time remaps so existing paintings keep their
look (old 1=neutral saturation remaps to 0=neutral).

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

Assets/Shaders/PlayerCamo.hlsl

@@ -3,7 +3,7 @@
 
 // Camouflage lighting for the player avatar. Goal: keep the player painted to match its
 // surroundings while de-emphasising the 3D FORM, so a correctly painted avatar is harder to spot.
-// Knobs - _HalfLambert at 0 and _HalfLambertBrightness at 0 => byte-identical URP/Lit:
+// Knobs - _HalfLambert 0, _HalfLambertBrightness 0 and _Saturation 0 => byte-identical URP/Lit:
 //
 //   _HalfLambert           (0..1): form-flattening diffuse over two segments -
 //                                  0   -> saturate(N.L)    plain Lambert (no-op)
@@ -14,9 +14,16 @@
 //                                  (operates on the shading term, not a view-/light-bent normal, so
 //                                  there is no bright/dark flip when orbiting). The DIRECT specular
 //                                  highlight (a strong shape cue) is faded out with it, gone at 1.
-//   _HalfLambertBrightness (-1..1): additive shift of the (flattened) diffuse term, default 0. Tunes
-//                                  the body brighter/darker to match the scene tone (e.g. flatten to
-//                                  1, then dial this down to sink into a dark scene). Clamped at 0.
+//   _HalfLambertBrightness (-1..1): GENERAL brightness (exposure) on the WHOLE shaded body - diffuse,
+//                                  ambient/GI AND specular - as a final multiply (1 + value), default
+//                                  0 = neutral. NO LONGER tied to the half-Lambert diffuse term (the
+//                                  "HalfLambert" in the name is legacy): dial down to sink the body
+//                                  into a dark scene, up to lift it into a bright one. Applied in
+//                                  CamoForwardFragment, before fog and the X-ray glow.
+//   _Saturation           (-1..1): colour saturation of the shaded body, default 0 = neutral. -1 =
+//                                  greyscale, <0 = muted (blends into muted scenes), >0 = punchier.
+//                                  Luma-preserving lerp(grey, colour, 1 + _Saturation) toward Rec.709
+//                                  grey, same final stage as brightness.
 //   _SpecularDampen        (0..1): scales down the DIRECT specular highlight (a strong shape cue) on
 //                                  top of the _HalfLambert fade.
 //
@@ -29,7 +36,8 @@
 // Declared OUTSIDE UnityPerMaterial (LitInput.hlsl owns that CBUFFER). The player is a handful of
 // instances, so the resulting SRP-batcher break is irrelevant.
 half _HalfLambert;
-half _HalfLambertBrightness;
+half _HalfLambertBrightness; // legacy name: now a GENERAL brightness/exposure (CamoForwardFragment), not a half-Lambert-only shift
+half _Saturation;
 half _SpecularDampen;
 
 // --- Painted height (from the occlusion channel) ---
@@ -103,13 +111,11 @@ half3 LightingPhysicallyBasedCamo(BRDFData brdfData, BRDFData brdfDataClearCoat,
     //   0   -> saturate(N.L)     plain Lambert (no-op, byte-identical URP/Lit)
     //   0.5 -> N.L * 0.5 + 0.5    classic half-Lambert (soft terminator, no hard shadow line)
     //   1   -> 1                  fully flat: the direct diffuse no longer reveals the 3D form.
-    // _HalfLambertBrightness then shifts the whole (flattened) term up/down to tune the body tone;
-    // clamped at 0 so it never produces negative light.
+    // (Brightness is NOT applied here anymore - it is a general final-color exposure in CamoForwardFragment.)
     half classicHL = NdotL * 0.5h + 0.5h;            // already in [0,1] for N.L in [-1,1]
     half t1 = saturate(_HalfLambert * 2.0h);         // 0..1 across _HalfLambert in [0, 0.5]
     half t2 = saturate(_HalfLambert * 2.0h - 1.0h);  // 0..1 across _HalfLambert in [0.5, 1]
-    half diffuseTerm = lerp(lerp(ndlSat, classicHL, t1), 1.0h, t2);
-    diffuseTerm = max(0.0h, diffuseTerm + _HalfLambertBrightness);
+    half diffuseTerm = lerp(lerp(ndlSat, classicHL, t1), 1.0h, t2); // in [0,1], no negative light
 
     half3 atten = lightColor * lightAttenuation;
     half3 diffuseRadiance  = atten * diffuseTerm; // flattened + brightness-shifted
@@ -291,6 +297,16 @@ void CamoForwardFragment(
     InitializeBakedGIData(input, inputData);
 
     half4 color = UniversalFragmentCamo(inputData, surfaceData);
+
+    // Camo body-tone grade on the WHOLE shaded body (direct + ambient/GI + specular): a GENERAL
+    // brightness/exposure and a saturation control - camo tools to sink/lift the body tone and to
+    // mute/punch its colour to match the scene. Applied before fog (part of the body look) and before
+    // the X-ray reveal glow below, so the reveal keeps its authored intensity. Neutral at brightness 0
+    // / saturation 0 (x1 multiply, no-op lerp) => byte-identical to stock when the camo knobs are off.
+    color.rgb *= 1.0h + _HalfLambertBrightness;
+    half camoLuma = dot(color.rgb, half3(0.2126h, 0.7152h, 0.0722h)); // Rec.709 luma
+    color.rgb = lerp(camoLuma.xxx, color.rgb, 1.0h + _Saturation);
+
     color.rgb = MixFog(color.rgb, inputData.fogCoord);
 
     // X-Ray reveal glow on the VISIBLE parts. URP draws the SRPDefaultUnlit XRayOverlay pass BEFORE

Assets/Shaders/PlayerCamoLit.shader

@@ -12,10 +12,12 @@ Shader "Custom/PlayerCamoLit"
 {
     Properties
     {
-        // --- Camouflage knobs (both 0 => identical to URP/Lit) ---
+        // --- Camouflage knobs (HalfLambert 0, Brightness 0, Saturation 0 => identical to URP/Lit) ---
         [Header(Camouflage)]
         _HalfLambert("Half Lambert (0 none, 0.5 classic, 1 flat)", Range(0.0, 1.0)) = 0.5
-        _HalfLambertBrightness("Half Lambert Brightness Shift", Range(-1.0, 1.0)) = 0.0
+        // Legacy property name; now a GENERAL brightness/exposure on the whole shaded body (see PlayerCamo.hlsl).
+        _HalfLambertBrightness("Brightness (general exposure, 0 = neutral)", Range(-1.0, 1.0)) = 0.0
+        _Saturation("Saturation (0 = neutral, -1 = greyscale, >0 = punchier)", Range(-1.0, 1.0)) = 0.0
         _SpecularDampen("Specular Dampen", Range(0.0, 1.0)) = 0.5
 
         // Specular vs Metallic workflow