BlendTree input and output sockets can now be registered via the AnimGraphResource.

src/AnimGraph/AnimGraphData.h

@@ -161,7 +161,7 @@ struct Socket {
   SocketValue m_value = {0};
   std::string m_value_string;
   union SocketReference {
-    void* ptr;
+    void* ptr = nullptr;
     void** ptr_ptr;
   };
   SocketReference m_reference = {0};
@@ -418,7 +418,7 @@ struct NodeDescriptorBase {
     return socket->GetValue<T>();
   }
 
-  virtual void UpdateFlags(){};
+  virtual void UpdateFlags() {};
 
  protected:
   Socket* FindSocket(const char* name, std::vector<Socket>& sockets) {

src/AnimGraph/AnimGraphResource.h

@@ -276,6 +276,73 @@ struct AnimGraphResource : AnimNodeResource {
   bool LoadFromFile(const char* filename);
 
   void CreateBlendTreeInstance(AnimGraphBlendTree& result) const;
+
+  template <typename T>
+  bool RegisterBlendTreeInputSocket(const std::string& socket_name) {
+    Socket socket;
+    socket.m_name = socket_name;
+    socket.m_type = GetSocketType<T>();
+    socket.m_type_size = sizeof(T);
+
+    return RegisterBlendTreeInputSocket(socket);
+  }
+
+  bool RegisterBlendTreeInputSocket(const Socket& socket) {
+    AnimNodeResource* input_node = m_blend_tree_resource.GetGraphInputNode();
+
+    std::vector<Socket> input_sockets =
+        input_node->m_socket_accessor->m_outputs;
+    std::vector<Socket>::const_iterator iter = std::find_if(
+        input_sockets.begin(),
+        input_sockets.end(),
+        [&socket](const Socket& input_socket) {
+          return socket.m_name == input_socket.m_name;
+        });
+
+    if (iter != input_sockets.end()) {
+      std::cerr << "Error: cannot register input socket as socket with name '"
+                << socket.m_name << "' already exists!" << std::endl;
+      return false;
+    }
+
+    input_node->m_socket_accessor->m_outputs.push_back(socket);
+    m_socket_accessor->m_inputs = input_node->m_socket_accessor->m_outputs;
+
+    return true;
+  }
+
+  template <typename T>
+  bool RegisterBlendTreeOutputSocket(const std::string& socket_name) {
+    Socket socket;
+    socket.m_name = socket_name;
+    socket.m_type = GetSocketType<T>();
+    socket.m_type_size = sizeof(T);
+
+    return RegisterBlendTreeOutputSocket(socket);
+  }
+
+  bool RegisterBlendTreeOutputSocket(const Socket& socket) {
+    AnimNodeResource* output_node = m_blend_tree_resource.GetGraphOutputNode();
+
+    std::vector<Socket> output_sockets =
+        output_node->m_socket_accessor->m_inputs;
+    std::vector<Socket>::const_iterator iter = std::find_if(
+        output_sockets.begin(),
+        output_sockets.end(),
+        [&socket](const Socket& input_socket) {
+          return socket.m_name == input_socket.m_name;
+        });
+
+    if (iter != output_sockets.end()) {
+      return false;
+    }
+
+    output_node->m_socket_accessor->m_inputs.push_back(socket);
+    m_socket_accessor->m_outputs = output_node->m_socket_accessor->m_inputs;
+
+    return true;
+  }
+
   void CreateStateMachineInstance(AnimGraphStateMachine& result) const;
 
  private: