<b>In Depth Review of Behavior in 3D Software</b>

<p dir="ltr">This thesis explores the concept of behavior as a core element in software systems and its role in the domain of 3D scene description. It begins by establishing foundational definitions of "behavior" across software engineering, organizational processes, and computational models, distinguishing it from but also integrating it with notions of function. Through a cross-domain literature review, the work examines behavior specification methods in engineering, civil construction, multimedia systems, defense simulations, human modeling, and artificial intelligence. The thesis evaluates various formalisms including state machines, temporal logic, process algebras, UML diagrams, ontologies, and architecture description languages, emphasizing their relevance to software behavior modeling.</p><p dir="ltr">Building on this foundation, the study investigates how behavior can be represented in 3D environments using tools like behavior trees, animation curves, and physics engines. It focuses on Pixar’s Universal Scene Description (USD) as a rising standard for scene representation, noting its strengths in modularity, extensibility, and interoperability across platforms like Unreal Engine, Omniverse, and Maya. Despite its flexibility, USD lacks native constructs for behavior specification. This work highlights how behaviors can currently be approximated through time-sampled animations, light movement, and custom schema authoring. A prototype USD scene is provided, demonstrating a cube with sinusoidal motion and an orbiting sphere light defined via direct .usda scripting.</p><p dir="ltr">The thesis concludes by proposing a pathway for extending USD to support richer behavior models through schema formalization or external tooling. It argues for a standardized behavioral specification within the USD ecosystem to bridge the gap between static scene description and dynamic, interactive 3D experiences.</p><p dir="ltr"><br></p>