feat: Add API for requesting a new mesh from the MeshManager

graphics/include/gz/common/MeshManager.hh

@@ -128,6 +128,13 @@ namespace gz
       /// \param[in] _name the name of the mesh
       public: bool HasMesh(const std::string &_name) const;
 
+      /// \brief Create an empty mesh and register it by name. If the mesh
+      /// already exists, returns nullptr.
+      /// \param[in] _name the name of the new mesh
+      /// \return a mutable pointer pointing to the newly allocated mesh, or
+      /// nullptr if the mesh name is already claimed.
+      public: common::Mesh *CreateMesh(const std::string &_name);
+
       /// \brief Create a sphere mesh.
       /// \param[in] _name the name of the mesh
       /// \param[in] _radius radius of the sphere in meter

graphics/src/MeshManager.cc

@@ -261,6 +261,21 @@ void MeshManager::AddMesh(Mesh *_mesh)
     this->dataPtr->meshes[_mesh->Name()] = _mesh;
 }
 
+//////////////////////////////////////////////////
+Mesh *MeshManager::CreateMesh(const std::string &_name)
+{
+  if (this->HasMesh(_name))
+  {
+    gzerr << "Mesh [" << _name << "] already exists." << std::endl;
+    return nullptr;
+  }
+
+  Mesh *newMesh = new Mesh();
+  newMesh->SetName(_name);
+  this->dataPtr->meshes[_name] = newMesh;
+  return newMesh;
+}
+
 //////////////////////////////////////////////////
 const Mesh *MeshManager::MeshByName(const std::string &_name) const
 {

graphics/src/MeshManager_TEST.cc

@@ -425,4 +425,37 @@ TEST_F(MeshManager, MergeSubMeshes)
   EXPECT_EQ(math::Vector2d(0, 0.6), mergedSubmesh->TexCoordBySet(5u, 2u));
 }
 
+/////////////////////////////////////////////////
+TEST_F(MeshManager, CreateMesh)
+{
+  auto *mgr = common::MeshManager::Instance();
+  std::string meshName = "test_create_mesh";
+
+  // Pre-condition
+  EXPECT_FALSE(mgr->HasMesh(meshName));
+  EXPECT_EQ(nullptr, mgr->MeshByName(meshName));
+
+  // Create the mesh
+  common::Mesh *mutableMesh = mgr->CreateMesh(meshName);
+  ASSERT_NE(nullptr, mutableMesh);
+  EXPECT_EQ(meshName, mutableMesh->Name());
+
+  // Fetch the newly created mesh
+  const common::Mesh *cachedMesh = mgr->MeshByName(meshName);
+  ASSERT_NE(nullptr, cachedMesh);
+  EXPECT_EQ(mutableMesh, cachedMesh);
+  EXPECT_TRUE(mgr->HasMesh(meshName));
+
+  // Attempt to create the same mesh again should return nullptr safely
+  common::Mesh *duplicateMesh = mgr->CreateMesh(meshName);
+  EXPECT_EQ(nullptr, duplicateMesh);
+
+  // Verify original mesh is intact
+  const common::Mesh *verifyMesh = mgr->MeshByName(meshName);
+  EXPECT_NE(nullptr, verifyMesh);
+  EXPECT_EQ(meshName, verifyMesh->Name());
+
+  mgr->RemoveAll();
+}
+
 #endif