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Multi-modal data interaction

Contact: Karl-Johan Palmérius

Multisensory visualization with haptics is a growing area with a wide range of applications. The aim of this project is to approach the problem of dynamic volume data where the materials represented are deformed by the haptic probe. Currently a deformation framework which permits the user to interact with a finite element model derived from the volume data is being developed. This model will accurately reflect properties such as stiffness, elasticity and mass in ways that the surface and spring-damper models, common in haptics systems today, cannot. The main focus of the project is increasing the realism of the force feedback while maintaining the real-time simulation requirements. The challenge in the field has been achieving a compromise between the high refresh rate demand for haptic force feedback (~1 kHz) and realism.

Providing a realistic force feedback in real-time will have an impact in a number of areas but the most obvious is that of simulators for clinical procedures which will better reflect the behavior of the body when the tissue is deformed by the doctor's hand or instruments. It is also possible to use the deformation as additional information during the segmentation of the volumetric data. Other scientific disciplines will also benefit, however, as features of this methodology will be applicable to other areas including the study of haptics in (bio) chemistry, fluid dynamics and engineering. The model will be also extended to allow topological changes from cutting and suturing as would be found in a medical simulator.

The project is also concerned with the methods required to allow for interactive dynamics where physics-based models are used to simulate the behaviour of tissues and other deformable objects. This is important in applications such as virtual prototyping and especially in surgery simulation. High update rates are required to accurately simulate the frequency content of object-object contacts while the more reliable physics simulation is slow and CPU intensive. In this project we look at ways of saving processing power so that more effort can be used to increase realism. Levels-of-details and asynchronous regions allows for lower quality where quality is not needed, leaving more CPU power to the important regions. We study how the parameters controlling this quality will affect the feedback error and perception. Understanding how limitations in haptic perception can allow for graceful degradation in less important regions is a key to the successful implementation of such schemes.

Haptics feedback can be used in many applications for increased realism, increased body control in tasks and interaction, and to convey local information about virtual objects and data. It is of particular importance in the areas where vision is poor, physical control is of primary importance or where an additional perceptual channels can provide important information, such as surgery simulation, virtual prototyping and exploratory scientific visualization. In many such applications volumetric data has an important role. These have no explicit surfaces information and require special methods for haptic rendering.

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