From b9ab0e46e2a1bbd2538dbc123e03297ab4944126 Mon Sep 17 00:00:00 2001
From: bqqbarbhg <bqqbarbhg@gmail.com>
Date: Fri, 3 May 2024 20:46:26 +0300
Subject: [PATCH] Fix handling missing skins using ufbx importer

Previously, _asset_parse_skins() would mess with the order of skin indices.
However, the rest of the code expected these to match to ufbx skin indices.
To fix this, retain the original skin indices in FBXState::original_skin_indices.
---
 modules/fbx/fbx_document.cpp | 10 ++++------
 modules/fbx/fbx_state.h      |  1 +
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/modules/fbx/fbx_document.cpp b/modules/fbx/fbx_document.cpp
index 5f94a805660..6e9b85dc350 100644
--- a/modules/fbx/fbx_document.cpp
+++ b/modules/fbx/fbx_document.cpp
@@ -693,10 +693,7 @@ Error FBXDocument::_parse_meshes(Ref<FBXState> p_state) {
 
 				// Find the first imported skin deformer
 				for (ufbx_skin_deformer *fbx_skin : fbx_mesh->skin_deformers) {
-					if (!p_state->skin_indices.has(fbx_skin->typed_id)) {
-						continue;
-					}
-					GLTFSkinIndex skin_i = p_state->skin_indices[fbx_skin->typed_id];
+					GLTFSkinIndex skin_i = p_state->original_skin_indices[fbx_skin->typed_id];
 					if (skin_i < 0) {
 						continue;
 					}
@@ -2341,7 +2338,7 @@ Error FBXDocument::_parse_skins(Ref<FBXState> p_state) {
 	HashMap<GLTFNodeIndex, bool> joint_mapping;
 
 	for (const ufbx_skin_deformer *fbx_skin : fbx_scene->skin_deformers) {
-		if (fbx_skin->clusters.count == 0) {
+		if (fbx_skin->clusters.count == 0 || fbx_skin->weights.count == 0) {
 			p_state->skin_indices.push_back(-1);
 			continue;
 		}
@@ -2387,8 +2384,9 @@ Error FBXDocument::_parse_skins(Ref<FBXState> p_state) {
 			}
 		}
 	}
+	p_state->original_skin_indices = p_state->skin_indices.duplicate();
 	Error err = SkinTool::_asset_parse_skins(
-			p_state->skin_indices.duplicate(),
+			p_state->original_skin_indices,
 			p_state->skins.duplicate(),
 			p_state->nodes.duplicate(),
 			p_state->skin_indices,
diff --git a/modules/fbx/fbx_state.h b/modules/fbx/fbx_state.h
index d10550c2282..e52f47e0db3 100644
--- a/modules/fbx/fbx_state.h
+++ b/modules/fbx/fbx_state.h
@@ -53,6 +53,7 @@ class FBXState : public GLTFState {
 	HashMap<Pair<uint64_t, uint64_t>, GLTFTextureIndex, PairHash<uint64_t, uint64_t>> albedo_transparency_textures;
 
 	Vector<GLTFSkinIndex> skin_indices;
+	Vector<GLTFSkinIndex> original_skin_indices;
 	HashMap<ObjectID, GLTFSkeletonIndex> skeleton3d_to_fbx_skeleton;
 	HashMap<ObjectID, HashMap<ObjectID, GLTFSkinIndex>> skin_and_skeleton3d_to_fbx_skin;
 	HashSet<String> unique_mesh_names; // Not in GLTFState because GLTFState prefixes mesh names with the scene name (or _)