Assimp FBX Import support

Issues fixed:
- Updated assimp to latest and backported fixes into godot.
- Fixed file scale being ignored from FBX file.
- Fixed bone removal
- Implemented proper armature binding
- Fixed recursion not always going through the entire path
- Implemented assimp global scaling system
- Fixed assimp global scale process to support unit conversion
- Implemented proper fbx scaling
- Fixed asserts caused by missing faces in some models which could crash
- Fixed valid bone removal
- Fixed root node being overwriten by assimp which caused data loss
- Fixed armature construction so that it works with multiple roots
- Implemented basic support for FBX standard materials
- Refactoring to improve code quality and improve function reuse.
- Simplified node creation from assimp scene into subsections: create_light, create_mesh, create_bone.
- Creating meshes is now done after hierarchy is created so that the skeleton is always available.
- Added support to assimp to support file scale in all formats which call SetFileScale.
- Many other fixes provided into assimp.

Known issues:
- FBX pivots from Maya do not currently work. (workaround: for now use blender import and export to remove pivot tracks)
- Hierarchy creates an extra node for each mesh - this was done intentionally but we intended to do a pass to remove these as they're a required node.
- When an animated mesh has not executed any animation the rest pose is wrong.

Co-authored-by: K. S. Ernest (iFire) Lee <ernest.lee@chibifire.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/thirdparty/assimp/code/FBX/FBXMeshGeometry.cpp b/thirdparty/assimp/code/FBX/FBXMeshGeometry.cpp
index 44a0264ca0..5c9a0e309d 100644
--- a/thirdparty/assimp/code/FBX/FBXMeshGeometry.cpp
+++ b/thirdparty/assimp/code/FBX/FBXMeshGeometry.cpp
@@ -115,7 +115,6 @@ MeshGeometry::MeshGeometry(uint64_t id, const Element& element, const std::strin
 
     if(tempVerts.empty()) {
         FBXImporter::LogWarn("encountered mesh with no vertices");
-        return;
     }
 
     std::vector<int> tempFaces;
@@ -123,7 +122,6 @@ MeshGeometry::MeshGeometry(uint64_t id, const Element& element, const std::strin
 
     if(tempFaces.empty()) {
         FBXImporter::LogWarn("encountered mesh with no faces");
-        return;
     }
 
     m_vertices.reserve(tempFaces.size());
@@ -612,7 +610,10 @@ void MeshGeometry::ReadVertexDataMaterials(std::vector<int>& materials_out, cons
     const std::string& ReferenceInformationType)
 {
     const size_t face_count = m_faces.size();
-    ai_assert(face_count);
+    if(face_count <= 0)
+    {
+        return;
+    }
 
     // materials are handled separately. First of all, they are assigned per-face
     // and not per polyvert. Secondly, ReferenceInformationType=IndexToDirect