## 5 Conclusions  
This study investigates the differences in visual perception of virtual material reflection properties in a VR environment, using smoothness as a representative attribute. The article includes two experiments and the construction of mapping methods.  
In the first experiment, data is collected using a 2 AFC-designed experiment to facilitate the calculation of perception differences, and the psychometric scales of glossiness for people in virtual and real environments are obtained. In the second experiment, a material matching adjustment experiment is performed under the Cook-Torrance framework, exploring how each important parameter (albedo, metallic, smoothness, normal distribution) of PBR material in a virtual reality environment affects the material surface glossiness and extending the result of the psychometric scale construction experiment to the PBR rendering. Finally, the rendering equation is solved using numerical integration methods. The PBR material smoothness parameter is converted into a physical glossiness (GU) on the glossiness dimension of real material so that the glossiness perception between the real-world and VR can be compared on the same dimension. An accurate mathematical mapping curve is obtained to describe the difference through calculation, and corresponding design suggestions based on the results are given.  
It is worth noting that the experiments in this study were conducted using a VR head-mounted display, and the resulting findings are solely applicable to the optimization of VR-related applications. With the emergence of wearable display devices featuring higher resolutions, wider fields of view, and a broader range of brightness, the outcomes obtained in this study have certain limitations. Nonetheless, since Glossiness (GU) and PBR materials are widely used technologies in related fields, the experimental methods and mapping models employed in this article can be readily transferred and applied to other devices.  
The human visual system operates in an extremely complex manner, and the technology used for graphics rendering is rapidly evolving. This study focuses on mapping the visual perception of reflective properties, and while significant progress has been made in this area, there is still a need for further exploration of the depth and breadth of material perception differences in the context of VR. Based on the methodology of this study, there are several promising research directions that are worth exploring in the future, including:  
1. Developing quantitative methods based on psychology to measure other PBR material attributes (such as subsurface scattering intensity, transparency, etc.);
2. Investigating the impact of non-visual cues on material visual properties and their effect on VR immersion;
3. Examining the influence of perceptual constancy on material perception in VR;
4. Studying the representation of materials and its impact on perception, driven by emerging rendering technologies such as NERF.  
[PERSON] conceived the experiments, developed the prototype system, performed the Experiment 2, and wrote the paper; [PERSON] develops the plotting module, performed the Experiment 1 and reviewed the manuscript; [PERSON] conceived and supervised the experiments, and reviewed the manuscript. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Natural Science Foundation of China (No. 72271053), the National Natural Science Foundation of China (No. 71871056) and the Technology Funds of Fundamental Research Strengthening Plan (No. 2020-JCJQ-JJ-263).  
Not applicable.  
**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** The author would like to thank the contributors to this article and all the participants in the experiment.  
**Conflicts of Interest:** The authors declare no conflict of interest.