From 4d4a3c42f6ad17ba63ed55b29525b3d968de82a4 Mon Sep 17 00:00:00 2001
From: Oleg Bogdanov <boguscoder@fb.com>
Date: Sat, 28 Nov 2020 10:01:50 -0800
Subject: [PATCH] Fix for 3489 | Preserve morph targets when splitting by bone
 count

---
 .../SplitByBoneCountProcess.cpp               | 39 +++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/code/PostProcessing/SplitByBoneCountProcess.cpp b/code/PostProcessing/SplitByBoneCountProcess.cpp
index 1fd26c757..b39444859 100644
--- a/code/PostProcessing/SplitByBoneCountProcess.cpp
+++ b/code/PostProcessing/SplitByBoneCountProcess.cpp
@@ -408,6 +408,45 @@ void SplitByBoneCountProcess::SplitMesh( const aiMesh* pMesh, std::vector<aiMesh
             }
         }
 
+        // ... and copy all the morph targets for all the vertices which made it into the new submesh
+        if (pMesh->mNumAnimMeshes > 0) {
+            newMesh->mNumAnimMeshes = pMesh->mNumAnimMeshes;
+            newMesh->mAnimMeshes = new aiAnimMesh*[newMesh->mNumAnimMeshes];
+            
+            for (unsigned int morphIdx = 0; morphIdx < newMesh->mNumAnimMeshes; ++morphIdx) {
+                aiAnimMesh* origTarget = pMesh->mAnimMeshes[morphIdx];
+                aiAnimMesh* newTarget = new aiAnimMesh;
+                newTarget->mName = origTarget->mName;
+                newTarget->mWeight = origTarget->mWeight;
+                newTarget->mNumVertices = numSubMeshVertices;
+                newTarget->mVertices = new aiVector3D[numSubMeshVertices];
+                newMesh->mAnimMeshes[morphIdx] = newTarget;
+                
+                if (origTarget->HasNormals()) {
+                    newTarget->mNormals = new aiVector3D[numSubMeshVertices];
+                }
+                
+                if (origTarget->HasTangentsAndBitangents()) {
+                    newTarget->mTangents = new aiVector3D[numSubMeshVertices];
+                    newTarget->mBitangents = new aiVector3D[numSubMeshVertices];
+                }
+                
+                for( unsigned int vi = 0; vi < numSubMeshVertices; ++vi) {
+                    // find the source vertex for it in the source mesh
+                    unsigned int previousIndex = previousVertexIndices[vi];
+                    newTarget->mVertices[vi] = origTarget->mVertices[previousIndex];
+
+                    if (newTarget->HasNormals()) {
+                        newTarget->mNormals[vi] = origTarget->mNormals[previousIndex];
+                    }
+                    if (newTarget->HasTangentsAndBitangents()) {
+                        newTarget->mTangents[vi] = origTarget->mTangents[previousIndex];
+                        newTarget->mBitangents[vi] = origTarget->mBitangents[previousIndex];
+                    }
+                }
+            }
+        }
+
         // I have the strange feeling that this will break apart at some point in time...
     }
 }