## 5 Discussion
### Future Works  
Future works of this study can be further expanded in the following aspects:  
Subclassification of CAD drawing tasks: Currently, we have simplified the classification of CAD drawing tasks into basic modeling and complex surfacing. However, CAD drawing tasks are diverse and complex. Future research can analyze and classify different types of CAD drawing tasks in more detail, and investigate the performance and efficiency differences of VR free-form modeling and parametric CAD modeling in these specific tasks.  
Focus on technological trends: Free-form VR technology and traditional parametric CAD interfaces are constantly evolving and improving. Future researchers need to closely monitor the latest trends in these technologies to understand their development directions and their impact on CAD modeling. Researchers can explore breakthroughs in human-machine interface design and interaction methods to enhance user experience and operational efficiency.  
User feedback and design optimization: This study mentioned users' feedback and suggestions on the operation experience of VR and parametric CAD. Future researchers can further investigate user feedback and needs, and optimize the design of CAD modeling software based on this feedback. This includes improving the intuitiveness of the user interface, providing more learning resources and training content, and addressing issues and difficulties that users may encounter.  
Multimodal interaction and integration: Future research can focus on multimodal interaction and integration, combining VR free-form modeling and parametric CAD modeling with other technologies and devices. This may include gesture recognition, voice control, virtual reality, and augmented reality, to provide a richer and more flexible CAD modeling experience.  
In summary, future researchers can further expand the results and contributions of this study through more detailed analyses of CAD drawing tasks, with a focus on technological trends, user feedback and design optimization, as well as multimodal interaction and integration. These efforts will contribute to a better understanding and application of the value and potential of VR free-form modeling and parametric CAD modeling in practical applications.  
Conceptualization, Y.-M.F. and T.-L.K.; Methodology, Y.-M.F. and T.-L.K.; Formal analysis, T.-L.K.; Investigation, T.-L.K.; Resources, Y.-M.F.; Data curation, T.-L.K.; Writing--original draft, T.-L.K.; Writing--review & editing, Y.-M.F.; Supervision, Y.-M.F.; Funding acquisition, Y.-M.F. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Science and Technology Council of Taiwan, grant number MOST 111-2410-H-239-016-.  
This study was approved by the Human Research Ethics Committee at National Cheng Kung University (Approval No.: NCKU HREC-E-109-223-2).  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
Deidentified participant data supporting the findings of this study are available for an indefinite period of time from the corresponding author. The data can be accessed by professionals for research purposes by contacting the corresponding author directly.  
The authors declared no potential conflict of interest with respect to the research, authorship, and/or publication of this article.