From 3edcd5b7ee954fc6c74b21fdc3f8940707c50945 Mon Sep 17 00:00:00 2001
From: SashaRX <SashaRX@ya.ru>
Date: Thu, 6 Aug 2026 13:52:43 +0200
Subject: [PATCH] Preserve optimized vertex colors during replay

---
 Editor/Tools/LightmapTransferTool.cs |  2 ++
 Editor/Uv2AssetPostprocessor.cs      | 14 ++++++++++----
 Editor/Uv2DataAsset.cs               |  3 +++
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/Editor/Tools/LightmapTransferTool.cs b/Editor/Tools/LightmapTransferTool.cs
index 4e680229..c580063e 100644
--- a/Editor/Tools/LightmapTransferTool.cs
+++ b/Editor/Tools/LightmapTransferTool.cs
@@ -2621,6 +2621,7 @@ bool TryBuildSidecarEntry(MeshEntry entry, Mesh resultMesh, out MeshUv2Entry sid
                     return false;
 
                 var positions = sidecarMesh.vertices;
+                var colors = sidecarMesh.colors32;
                 var uv0List = new List<Vector2>();
                 (entry.originalMesh ?? resultMesh).GetUVs(0, uv0List);
 
@@ -2637,6 +2638,7 @@ bool TryBuildSidecarEntry(MeshEntry entry, Mesh resultMesh, out MeshUv2Entry sid
                     edgeWelded = entry.wasEdgeWelded,
                     vertPositions = positions,
                     vertUv0 = uv0List.ToArray(),
+                    optimizedColors = colors.Length == sidecarMesh.vertexCount ? colors : null,
                     schemaVersion = Uv2DataAsset.CurrentSchemaVersion,
                     toolVersion = Uv2DataAsset.ToolVersionStr,
                     sourceFingerprint = fp,
diff --git a/Editor/Uv2AssetPostprocessor.cs b/Editor/Uv2AssetPostprocessor.cs
index e79c45ca..a16f9af6 100644
--- a/Editor/Uv2AssetPostprocessor.cs
+++ b/Editor/Uv2AssetPostprocessor.cs
@@ -723,7 +723,7 @@ static bool ReplayOptimization(Mesh mesh, MeshUv2Entry entry, bool stale = false
             // ── Build optimized arrays via remap ──
             // If ground-truth vertex data is available, use it DIRECTLY for positions/normals/tangents.
             // This completely bypasses the remap for geometry, eliminating all remap-related vertex errors.
-            // The remap is only used for UV channels and colors (which aren't stored in ground truth).
+            // The remap is only used for UV channels and as a fallback for legacy color data.
             bool hasGroundTruth = entry.optimizedPositions != null && entry.optimizedPositions.Length == optCount;
 
             var optPos = new Vector3[optCount];
@@ -750,13 +750,19 @@ static bool ReplayOptimization(Mesh mesh, MeshUv2Entry entry, bool stale = false
                     System.Array.Copy(entry.optimizedNormals, optNormals, optCount);
                 if (optTangents != null && entry.optimizedTangents != null && entry.optimizedTangents.Length == optCount)
                     System.Array.Copy(entry.optimizedTangents, optTangents, optCount);
-
-                // UV channels, colors — from remap (UV0 is modified by weld, must come from raw FBX)
+                if (optColors != null && entry.optimizedColors != null && entry.optimizedColors.Length == optCount)
+                    System.Array.Copy(entry.optimizedColors, optColors, optCount);
+
+                // UV channels and legacy colors — from remap (UV0 is modified by weld,
+                // so it must come from the raw FBX). Optimized colors remain authoritative
+                // because merged and orphan vertices cannot always be reconstructed by remap.
+                bool remapColors = optColors != null &&
+                    (entry.optimizedColors == null || entry.optimizedColors.Length != optCount);
                 for (int i = 0; i < rawCount; i++)
                 {
                     int dst = remap[i];
                     if (dst < 0) continue;
-                    if (optColors != null) optColors[dst] = rawColors[i];
+                    if (remapColors) optColors[dst] = rawColors[i];
                     for (int ch = 0; ch < 8; ch++)
                     {
                         if (ch == 1 || optUvs[ch] == null) continue;
diff --git a/Editor/Uv2DataAsset.cs b/Editor/Uv2DataAsset.cs
index dab5eb79..17aafab9 100644
--- a/Editor/Uv2DataAsset.cs
+++ b/Editor/Uv2DataAsset.cs
@@ -175,6 +175,8 @@ public class MeshUv2Entry
         public Vector3[] optimizedNormals;
         /// <summary>All vertex tangents from the optimized mesh at Apply time.</summary>
         public Vector4[] optimizedTangents;
+        /// <summary>All vertex colors from the optimized mesh at Apply time.</summary>
+        public Color32[] optimizedColors;
 
         // ── Shell descriptors (v0.14.0+) ──
         /// <summary>Stable shell descriptors for the target mesh UV0 shells.</summary>
@@ -418,6 +420,7 @@ static void CopyEntryFields(MeshUv2Entry src, MeshUv2Entry dst)
             dst.optimizedPositions = src.optimizedPositions;
             dst.optimizedNormals = src.optimizedNormals;
             dst.optimizedTangents = src.optimizedTangents;
+            dst.optimizedColors = src.optimizedColors;
             dst.shellDescriptors = src.shellDescriptors;
             dst.vertexToSourceShellDescriptor = src.vertexToSourceShellDescriptor;
             dst.targetShellToSourceShellDescriptor = src.targetShellToSourceShellDescriptor;