3D Geometry is an Android application developed by DNHieu, available for free. It is an educational and reference program that provides a visualization tool for 3D geometry and modeling. The application comes with default shapes such as box, cone, sphere, octahedron, and prism. Users can create custom shapes by connecting input points and filling them to make 3D shapes.

The program's interface is user-friendly and easy to navigate. It allows users to save their scenes, and signed-up users' content can be saved on cloud storage. 3D Geometry is a great tool for students, teachers, and anyone interested in 3D geometry and modeling. It provides an interactive way to visualize and explore 3D shapes and their properties. Overall, 3D Geometry is a useful and practical application that can enhance the learning experience.