Mid-air haptic textures
Described is a method for instilling the haptic dimension of texture to virtual and holographic objects using mid-air ultrasonic technology. A set of features is extracted from imported images using their associated displacement maps. Textural qualities such as the micro and macro roughness are then computed and fed to a haptic mapping function together with information about the dynamic motion of the user's hands during holographic touch. Mid-air haptic textures are then synthesized and projected onto the user's bare hands. Further, mid-air haptic technology enables tactile exploration of virtual objects in digital environments. When a user's prior and current expectations and rendered tactile texture differ, user immersion can break. A study aims at mitigating this by integrating user expectations into the rendering algorithm of mid-air haptic textures and establishes a relationship between visual and mid-air haptic roughness.
1. A method for generating mid-air haptic textures comprising:
importing a texture image having macro texture features Mi and micro texture features mi by an offline component;
extracting, by the offline component, Mi and mi from the texture image and applying haptic mapping to sensation si where H[si]=f(si, mi, Mi) to generate an offline component output;
on a iterative basis:
a) detecting, by a mid-air tracking system, collision points between a moving human hand and a virtual object xi;
b) calculating, by the mid-air tracking system, the center of mass of the collision points X=μ(xi);
c) establishing, by the mid-air tracking system, projecting H[si] to X depending in part on the offline component output;
wherein extracting Mi and mi from the texture image uses a displacement map and avoids possible sensory conflicts due to inconsistency between the mid-air haptic texture and its visual representation.
2. The method as in claim 1 , wherein the center of mass of the collision points is not on the human hand.
3. The method as in claim 1 , wherein mi is calculated using a 2D autocorrelation function for a high-resolution image.
4. The method as in claim 3 , wherein the 2D autocorrelation function establishes whether an image contains periodic features.
5. The method as in claim 3 , wherein the 2D autocorrelation function is obtained by taking a discrete Fourier transform of the texture image and multiplying each coefficient with its complex conjugate before taking an inverse discrete Fourier transform.
6. The method as in claim 3 , wherein the 2D autocorrelation function is obtained by a power spectral density function that measures energy at each spatial scale.
7. The method as in claim 1 , wherein Mi is calculated by setting a circle haptic intensity to be proportional to the displacement map value at DM(X).
8. The method as in claim 7 , wherein strength of a haptic sensation is modulated between a minimum value corresponding to a vibrotactile threshold and a maximum output power of a mid-air haptic generator.