Haptics in Computer-Aided Design


Jian Zhang

Computer graphics has done a fairly good job in simulating the physical world on computer screen. This virtual world is still not realistic enough because an important sense, touching, is not included. By being able to touch objects in the virtual world, better mental models are constructed for a given data set. The understanding of the data set presented is also easier to go deeper since the user is more involved. By constructing a more realistic virtual world, many processes that are usually too dangerous, unredoable, inconvenient, or time-consuming become less dangerous, redoable, convenient, and time-saving. Medical training, virtual manufacture, and virtual assembly are good examples of applications of haptic rendering in the near future.

Our project is aiming at a medical training system. A medical device represented by a four-bar linkage and a layer of human tissue represented by a mesh, are displayed on screen. The user is able to feel the existence of the device and the mesh by touching them, feeling the force feedback via the Phantom. The user can "grab" a bar of the linkage and move it. The linkage will follow the motion of the user and at the same time be constrained by lengths of bars and their connection relationship. When the mesh is penetrated by any of the bars, the mesh begins to deform. The user can feel the force generated by the mesh deformation via Phantom. So far, we have been able to import the medical device model from a common CAD file format, DXF. In future work, we will substitute the plane mesh for more complex object surfaces like, say, human organs. We also plan to go from surface deformation to volume deformation. Furthermore, we will improve graphics so the image is more convincing.