Virtual Reality (VR) is an emerging technique that provides immersive experience for users. Due to the high computation cost of rendering real-time animation twice (for both eyes) and the resource limitation of wearable devices, VR applications often face performance bottlenecks and performanceoptimization plays an important role in VR software develop-ment. Performance optimizations of VR applications can be very different from those in traditional software as VR involves more elements such as graphics rendering and real-time animation. In this paper, we present the first empirical study on 183 real-world performance optimizations from 45 VR software projects. In particular, we manually categorized the optimizations in to 11 categories, and applied static analysis to identify how they affect different life-cycle phases of VR applications. Furthermore, we studied the complexity and design / behavior effects of performance optimizations, and how optimizations are different between large organizational software projects and smaller personal software projects. Our major findings include: (1) graphics simplification (24.0%), rendering optimization (16.9%), language / API optimization (15.3%), heap avoidance (14.8%), and valuecaching (12.0%) are the most common categories of performance optimization in VR applications; (2) game logic updates (30.4%) and before-scene initialization (20.0%) are the most common life-cycle phases affected by performance issues; (3) 45.9% of the optimizations have behavior and design effects and 39.3% of the optimizations are systematic changes; (4) the distributionsof optimization classes are very different between organizational VR projects and personal VR projects.

@inproceedings{NusratHZW21,
  title = {How Developers Optimize Virtual Reality Applications: A Study of Optimization Commits in Open Source Unity Projects},
  author = {Fariha Nusrat and Foyzul Hassan and Hao Zhong and Xiaoyin Wang},
  booktitle = {ICSE},
  year = {2021},
  doi = {10.1109/icse43902.2021.00052}
}