reduced number of elements and the fact that no matrix inversions are needed (only multiplications of matrices by vectors), result in a simulation that is fast and scalable, while enabling a full simulation of deformations and dynamics. It is important to stress that the REM model can simulate not only deformations caused by touch and gravity but also dynamic effects like the breast movements caused by walking and jumping. Figure 5 shows the breast simulated on different body postures and the effect of gravity applied on the volume.
Figure 5. The breast in different body postures.
The volume conservation property of the method enhances the accuracy and realism of the simulation. Large deformations, caused by touch and gravity acting on the breast, represent a difficult challenge for other simulation methods, but can be stably simulated by the REM.
3. Experimental Results Our prototype was implemented in C++ and OpenGL and runs on a standard PC at rates compatible with real time graphic and haptic interaction. To test and validate this prototype we acquired a number of 3D scans from a patient using a laser range scanner and defined the elasticity constants of the REM model based on breast tissue properties. Figure 3 shows the 3D scan of the patient’s torso. Using a 3D editor each breast is delimited on the torso and a REM mesh is built. Figure 1 shows the REM breast model being touched using a haptic interface. It is important to stress that the REM model can simulate not only deformations caused by touch and gravity but also dynamic effects like the breast movements caused by walking and jumping. Figure 5 shows the breast simulated on different body postures and the effect of gravity applied on the volume. The same breast can be simulated with