# Manipulating Underfoot Tactile Perceptions of Flooring Materials in Augmented Virtuality
## 2 Related Work
### Feet-Based Haptics  
Haptic and touch research focuses largely on hand interactions due to the high density of mechanoreceptors in our fingertips and their everyday use [39], yet our feet also contain a significant number of mechanoreceptors [40]. Our feet constantly experience tactile sensations while walking and moving. However, foot-based haptics have not been as extensively explored as hand-based haptics. Foot haptic devices have been developed to concentrate on specific tasks, such as stepping up [41], walking through deep snow [42], or simulating slipperiness [43] and friction [44]. [PERSON] et al. [45] designed a floor-tile-based haptic device replicating various ground materials using vibrotactile feedback. When combined with realistic audio and visual input, it can simulate a range of materials and a walkable area corresponding to the device's size. Similarly, [PERSON] et al. [46] designed a floor-tile-based haptic device that simulated texture and shape similar to textured paving tiles used in public spaces. This work provided insight into directional haptic cues to the foot and how they should be applied to provide the most perceivable haptics.  
Foot-based haptics can differ largely from hand-based haptics due to the interaction methods and the environment interacted in. Different terrains provide different haptics with unique interactions, such as water environments like rivers. [PERSON] et al. [47] created PropelWalker, a propeller-based haptic device that provides resistance to the lower leg to simulate wading through knee-high water. [PERSON] et al. [48] took this a step further, creating a haptic environment that made use of water to provide haptic feedback and providing the unique interactions that come from liquid-based environments.  
Auditory feedback plays a crucial role in underfoot interactions, influencing the overall tactile experience. As we walk, we constantly receive information about the material beneath our feet through audio cues or their absence. Research by [49; 50; 51] investigated foot-based tactile devices that deliver audio vibrotactile haptic feedback for walking in virtual spaces. While the added feedback did not significantly alter the overall perception, user experience was enhanced with a preference towards the added feedback and improved realism.  
Carpets, like hair and fur, are composed of a multitude of fibrillar structures packed together that behave differently from most objects. Research has not investigated the tactile properties of carpet flooring. Nevertheless, [PERSON] et al. [52] developed HairTouch, a system that offers stiffness and roughness tactile feedback using adjustable brush hair structures. Lowering the height of the fibres increases rigidity, making the material feel stiffer and rougher due to reduced fibre bending. Similarly, [PERSON] et al. [53] employed 3D-printed hair structures of varying lengths combined with visual dominance to enhance virtual textures.  
Tactile perception studies have largely focused on hand-based interactions. Given the constant interaction of our feet on the floor, feet-based tactile interactions can provide insightful information on the tactile input we perceive walking around day to day. We aim to open up research on feet-based haptics by investigating how the tactile perception of our feet is impacted by changing visuals.  
In this research, we investigate how changes in visual appearance influence the tactile perception of materials and develop a system that displays various overlays of flooring materials in Augmented Virtuality.