Developing and maintaining a VR system is a very difficult task, requiring in-depth knowledge in many disciplines. The difficulty lies in the complexity of having to simultaneously consider many system goals, some of which are conflicting.This book is organized so that it follows a spiral development process for each stage, describing the problem and possible solutions for each stage. Much more hands-on than other introductory books, concrete examples and practical solutions to the technical challenges in building a VR system are provided.Part 1 covers the very basics in building a VR system and explains various technical issues in object modeling and scene organization. Part 2 deals with 3D multimodal interaction, designing for usable and natural interaction and creating realistic object simulation. Primarily written for first level graduates, advanced undergraduates and IT professionals will also find this a valuable guide.