Fig. 4From: Enabling visually impaired people to learn three-dimensional tactile graphics with a 3DOF haptic mouseThe displacement of the lever is expressed in terms of spherical coordinates. \(\varphi\) is the elevation angle, \(\theta\) represents the azimuth angle and n the unitary vector normal to the surface. Left: digital rendering of an arbitrary scalar field. Right: Local representation of the scalar field displayed with TAMO3Back to article page