The Vuforia native samples rely on the use of OpenGL ES (version 1.1 and 2.0) for rendering the video background as well as the 3D augmentation.
The following FAQs address the most common issues and topics on Vuforia SDK samples and the use of OpenGL ES.
How to replace the teapot 3D model:
https://developer.vuforia.com/forum/faq/android-how-do-i-replace-teapot