# The Effect of Depth Information on Visual Complexity Perception in Three-Dimensional Textures
## 4 Discussion  
The experimental results revealed that both texture characteristics and depth information, had significant impacts on the evaluation of visual complexity in a VR space. Depth, roughness, three-dimensionality, directionality, regularity, and understandability of the textures were the factors that most influenced the visual complexity perception, as found by analyzing the participants' responses to the questionnaire given after the experiment.  
We compared the visual complexity of three sets of texture images under 2D and 3D conditions. All three sets of texture images indicated greater visual complexity by approximately one score under 3D conditions. This may have been due to the introduction of additional depth information in the 3D textures, which implied that the amount of information in a 3D texture was greater than that in its corresponding 2D texture, thereby resulting in increased visual complexity perception.  
It is worth noting that the understandability of a texture has been considered to be a major factor affecting visual complexity [24; 25]. Understandability represents how easily a participant can comprehend a particular stimulus. Textures with higher understandability usually have lower perceived visual complexity. When additional depth information is introduced to a 3D texture, the additional information may help the participants to comprehend the texture more easily, thereby  
Figure 3: Pairwise comparison for mean complexity scores between 2D and 3D textures. Error bars indicate \(SD\) (Standard deviation). \({}^{*}\) means \(p<0.05\), \({}^{**}\) means \(p<0.01\).  
reducing the visual complexity of the 3D texture. However, the experimental results did not support this hypothesis. This may be because of the characteristics of the texture stimuli which we selected for the experiment. The understandability of these texture stimuli was relatively high, and the additional depth information did not significantly improve the understandability. We plan to conduct more experiments on other texture stimuli in the future in order to explore this further.  
The experimental results also revealed that textures with higher complexity had higher standard deviations, and 3D textures with depth information had higher standard deviations than 2D textures, as shown in Figure 3. This can also be attributed to additional depth information provided in 3D textures. The additional depth cues might have resulted in more factors that affect visual complexity, making it more difficult for participants to obtain consistent results in evaluation of complexity.  
Furthermore, the experimental results shown in Table 3 indicate that the mean difference between the complexity of a texture in 2D and 3D was proportional to the maximum depth of its 3D image (_door_: maximum depth = 21.07 mm, _dot_: maximum depth = 7.89 mm, _stone_: maximum depth = 18.01 mm). There was a significant interaction between the depth and texture in visual complexity perception. This indicates that for different textures, depth information had different effects on perception of visual complexity. In the future, we aim to perform more experiments to verify whether the interaction between depth and texture in visual complexity perception is caused by the characteristics of different textures (directionality, density, regularity, etc.) or is only related to the maximum depth of a texture.