**4.5.4 Tactile integration**

The tactile rederer receives information from the contact response module, in particular the position of the contact points, relative velocities and pressures. This information is then used to control the tactile device, in which the 30 pins can be controlled using a single frequency of a sinusoid, whose intensity and phase can be changed for every pin. The rendering is performed by following the approach proposed in (D Allerkamp et al., 2007) and later integrated in (Fontana et al., 2007) although with a different device and with multiple degree of freedom in control. The idea is to start from a geometrical representation of the local feature of the textiles obtained from edge extraction of high resolution photos. Then the local height field is repeated over the textile surface and the position of the tactile actuators in real space is mapped to the surface of the textile. Taking into account the motion of the actuator over the surface the height local information is transformed into a profile of heights along the line of motion that can be transformed into a frequency signal. This signal is the one used for controlling the distinct pins. Differently from the cited work in which two frequencies where selected, this work uses a single sinusoidal frequency but different intensities and phases of the pins.

This model has to be extended for taking into account pressure over the textile and relative velocity. These two featured have indeed the effect of modifying the height of the surface and alter the frequencies of generated signal. Multiple contact points on the surface nearby the tactile actuator have the effect of cumulating the alteration on the surface due to pressure and velocity.
