I need to develop a kind of Paint, only for 3D. The main feature of the program is an ability to "draw" 3D models in 3D space.
I have a permission to use any package / tool / library I choose, including commercial products. Main platform is Windows, and it should be a desktop application. It could be in C++, C#, or Java.
I have much 3D programming experience in DirectX/Direct3D, OpenGL, Java3D, Helix Toolkit etc. However all the libraries/SDKs that I know are lacking this very important interactive drawing feature "right out of the box". I am not familiar with Unity or Unreal, do they have this option? Are there other libraries better suited for my purpose? What would be the best tool for the task if taking a learning curve into consideration?