# Manipulating Underfoot Tactile Perceptions of Flooring Materials in Augmented Virtuality
## 2 Related Work
### Visual and Tactile Perception  
Vision plays a critical role in our perception of objects and expectations when interacting with them. With visual input making up more than 70% of our sensory input [29], even before we approach an object, visual input provides information about it. As we continue to interact with objects, we develop a mental model of the materials we come into contact with, and the visual appearance of these objects is essential in identifying and determining how to interact with them [12; 13]. However, the bimodal relationship between inputs varies based on the object being interacted with. For instance, a photograph offers visual information but little tactile information, whereas other objects have a preference towards tactile information as the visual texture offers little, like with sandpaper [30]. Our expectations of the physical environment are impacted by what we visually see and information from past experiences. Even if the virtual world does not match the physical space, the wearer tends to avoid virtual areas that would normally provide consequences in the physical space [31]. This control of visual sensations allows for haptic illusions--perceived sensations that do not exist physically and can be created through auditory control as well [32].  
In some cases, both visual and tactile modalities are necessary to accurately determine a material. For example, [PERSON] et al. [14] explored how participants perceived the roughness of a range of materials with only one modality of either visual or touch. Their findings revealed that the modality affected the participants' perception of the materials. However, visual feedback alone is not always enough to identify the material, and a combination of visual and tactile feedback is needed to provide enough information on the material [15; 16]. While one modality may influence our perception of an object more than others, a combination of modalities is often the preferred choice, providing the most positive experience [33]. Moreover, the relationship between visual and tactile feedback can be used to alter tactile perception by changing the visual appearance. Research has shown that superimposing digital imagery on objects can change a user's perception of shape, roughness, hardness, and stiffness [34; 35]. The form of virtual content also influences how an object is perceived, as the amount of virtual content varies. A study by [PERSON] et al. [36] found that a piston shown in VR was perceived as stiffer in 60% of cases against an AR display, even though physical stiffness remained constant. Other factors such as variations of a material and past experiences can impact haptic impressions when combined with altering visual textures [37]. Dynamic visuals that change differently from the physical object have also been found to alter tactile perception. For instance, by virtually displaying an object to be deforming more than how it is being interacted with, the object is perceived as softer [17; 18]. Additionally, [PERSON] et al. [38] explored the perceived roughness of a range of materials with various virtual displays and found that the range of virtual materials could be represented using only two physical materials.  
Research has shown that there is a relation between visual and tactile feedback and that changing visual feedback can impact tactile feedback. We decided to ask the question \"Could multiple flooring materials be simulated using a singular material with multiple visual appearances?\". To help answer this, we decided to focus on quantifying the degree that the tactile perception is impacted by changing visual appearance.