Haptic display of 3D liquids for interactive applications

Abstract

We challenge ourselves to allow a user to feel how to stir a pool of 3D fluid in a virtual environment. Fluids are objects where the shape can not be defined using conventional polygons, and the graphical rendering and haptic rendering are purely based on mathematical calculation from the Navier-Stokes equation. Through a haptic probe the user is able to introduce perturbations in a pool of simulated liquid, and real-time haptic force feedback enables visualization of the effects of this interaction. We innovate by developing efficient methods for realtime interaction with the simulation of viscous incompressible fluids, suitable for higly interactive applications such as computer games. We focus on the problem of producing haptic visualization of real-time simulation that resembles the tactile sensation the user perceives from real fluids.

Enabling Interaction with Virtual Fluids and Mixed Media using a High Dexterity Hand Exoskeleton

“…For more realistic fluid interactions, Wang and Wang proposed a hybrid method that also used SPH for the fluid, but added a flexible proxy modeled through FEM running in real time with hardware acceleration [14]. In comparison, Vines, Mora and Lee used a more simplified approach to calculate fluid forces [15]. Viscosity forces were approximated as proportional to velocity of the haptic interface point, and inertia forces were regarded as proportional to the extension of a virtual mass-spring system attached to the haptic interface point [16].…”

“…Using the recently-developed hand-arm exoskeleton Exodex Adam [17], [18] (Section II) of the the German Aerospace Center (DLR), we implement a simplified method (Section III) to render fluid forces with high update rates, similar to the approach in [15]. To test human perception capabilities of the rendered fluids we conducted two humanin-the-loop experiments.…”

“…Thus, a trade-off between accuracy and sufficiency needs to be made. Vines, Mora and Lee [15] identified that a key aspect to approximate perceivable fluid flow behavior is the opposing forces of the fluid to motion (drag). Inspired by this work, we propose to restrict the rendering of fluid forces for complex haptic interfaces like the used exoskeleton to only represent those drag forces ( Fig.…”

“…Substituting this into (1) yields a simple analytical expression for drag force, similar to the equation proposed by Vines, Mora and Lee to render the viscosity [15]. This can be computed quickly, allowing high update frequencies for the real time robot interaction.…”