Programming language support for virtual environments

Developing 3D virtual environments requires an advanced level of programming expertise in a wide range of programming domains including 3D graphics, networking, user interfaces and audio programming. To compound the problem, virtual environments have strong real time performance requirements. The complexity of developing these kinds of applications comes from two sources: first, the requirements of the virtual environment itself, with its dynamics and size. The second is the programming language used in development, with its strengths and also the limitations it imposes. Unfortunately, most of the tools and libraries necessary for developing virtual worlds are available mainly with low level system programming languages such as C and C++. The complexity and the amount of code required in this family of languages contribute to the overall complexity of virtual world applications making the process of building such applications a challenging process. Because the gap between language and application domain is high, a language for writing virtual environments is needed. Very high level languages such as Python and Unicon, compared to languages such as C, offer very high level programming semantics, syntax, data structures, and rich APIs with built-in support covering a wide range of programming activities such as I/O. With these language characteristics, programs can be made significantly more compact and therefore less complex. However, these very high level languages lack features essential to developing virtual worlds, and more importantly, they fall short of high performance and scalability requirements of virtual environments. This dissertation presents a language/application co-design approach for software development of virtual world. Both the application and the programming language itself evolve over time to meet new requirements. This approach is used in the development of a collaborative virtual environment called CVE, and its implementation language, Unicon. The focus of the co-design is on language extensions for virtual environment development. These extensions include 3D graphics, concurrent programming and 3D interaction. The language is improved to address the complexities and requirements that arose at the application level. This dissertation answers two main questions: 1) Is it possible to utilize a very high level language with a legacy virtual machine in virtual worlds development where performance is critical? 2) How and where does such a language need to be extended and modified both at the language level and in its implementation to meet the requirements of a multi-user virtual environment? The goal is to reduce the complexity and cost of developing virtual environments, enabling less experienced programmers to participate in developing such applications. The dissertation does not create a virtual world or a new programming language; instead it uses an existing language and complements it with very high level features. The main contribution of this dissertation is the novel design and integration of new features into a very high level goal-directed language. These features not only provide very high level support for virtual environments, but also meet the language design guidelines, maintain backward compatibility, and have very little impact on the syntax. The benefits of the new features are not specific to virtual worlds.