Merge branch 'main' of https://github.com/cdbharath/Open3D into main

CHANGELOG.md

@@ -32,6 +32,7 @@
 -   Fix mis-configured application .desktop link for the Open3D viewer when installing to a custom path (PR #6599)
 -   Fix regression in printing cuda tensor from PR #6444 🐛
 -   Add Python pathlib support for file IO (PR #6619)
+
 -   Fix log error message for `probability` argument validation in `PointCloud::SegmentPlane` (PR #6622)
 -   Fix macOS arm64 builds, add CI runner for macOS arm64 (PR #6695)
 -   Fix KDTreeFlann possibly using a dangling pointer instead of internal storage and simplified its members (PR #6734)

cpp/open3d/geometry/TriangleMesh.cpp

@@ -52,6 +52,7 @@ TriangleMesh &TriangleMesh::Rotate(const Eigen::Matrix3d &R,
 
 TriangleMesh &TriangleMesh::operator+=(const TriangleMesh &mesh) {
     if (mesh.IsEmpty()) return (*this);
+    bool is_empty = IsEmpty();
     size_t old_vert_num = vertices_.size();
     MeshBase::operator+=(mesh);
     size_t old_tri_num = triangles_.size();
@@ -74,21 +75,22 @@ TriangleMesh &TriangleMesh::operator+=(const TriangleMesh &mesh) {
     if (HasAdjacencyList()) {
         ComputeAdjacencyList();
     }
-    if (mesh.HasTriangleUvs()) {
+    if (mesh.HasTriangleUvs() && (HasTriangleUvs() || is_empty)) {
         size_t old_tri_uv_num = triangle_uvs_.size();
         triangle_uvs_.resize(old_tri_uv_num + mesh.triangle_uvs_.size());
         for (size_t i = 0; i < mesh.triangle_uvs_.size(); i++) {
             triangle_uvs_[old_tri_uv_num + i] = mesh.triangle_uvs_[i];
         }
     }
-    if (mesh.HasTextures()) {
+    if (mesh.HasTextures() && (HasTextures() || is_empty)) {
         size_t old_tex_num = textures_.size();
         textures_.resize(old_tex_num + mesh.textures_.size());
         for (size_t i = 0; i < mesh.textures_.size(); i++) {
             textures_[old_tex_num + i] = mesh.textures_[i];
         }
     }
-    if (mesh.HasTriangleMaterialIds()) {
+    if (mesh.HasTriangleMaterialIds() &&
+        (HasTriangleMaterialIds() || is_empty)) {
         size_t old_tex_num = textures_.size();
         size_t old_mat_id_num = triangle_material_ids_.size();
         triangle_material_ids_.resize(old_mat_id_num +