I've recently received several customer inquiries regarding using Insight3D and the rest of AGI Components in a C++ development environment. This is often desirable because it allows you to integrate Insight3D and AGI Components into an existing C++ codebase, and can also make it easier to use native C++ libraries in a new Insight3D application.
Not only is this entirely possible with C++/CLI, but Insight3D is capable of being easily integrated into many common user interface frameworks in that environment, including MFC, Windows Forms, and Qt.
As an example, I've posted a simple C++/CLI example using Insight3D and AGI Components in the context of a Windows Forms application to help you get started.
You should note that the above example references assemblies in the default install location for AGI Components for .NET 2010 r2. You may need to update the references in the project to point to your particular install location. From the project properties, navigate to Common Properties->Framework and References, remove the references to AGI.Foundation.*, then add references to the same assemblies from your particular AGI Components installation. Similarly, if you get an error in relation to licenses, you may have to remove licenses.licx from the project and add the licenses.licx file from the Assemblies directory in your AGI Components installation.