D. Nelson, D. Johnson, and E. Cohen, "Haptic rendering of surface-to-surface sculpted model interaction," in Symposium on Haptic Interfaces for Virtual Environments and Teleoperator Systems (HAPTICS 1999.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....haptics based applications because of their dominance in the CAD CAM fields. Object modeled as NURBS surfaces can be rendered interactively at varying levels of resolution with bounded error [15] This makes them attractive for use in graphically intensive applications. Another set of algorithms [14, 18, 25] have been developed for direct haptic rendering of NURBS based models, including an extension to surface surface interaction which removes the single point of intersection constraint commonly found in haptic rendering. Terzopoulos and Qin [24] have developed D NURBS, a physics based ....

D. Nelson, D. Johnson, and E. Cohen. Haptic rendering of surface-to-surface sculpted model interaction, 1999, http://citeseer.nj.nec.com/nelson99haptic.html.

....reduced coordinates. We use sphere trees built from polyhedral approximations of our models for collision detection. Approximate contact coordinates are computed from the minimum distance reported by the sphere tree. Before using these coordinates we apply a few Newton iterations, as described in [27], to find a better approximation of the contact point on the smooth surfaces. 4 Micro simulation of Contact Interactions 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0 0.5 1 1.5 2 2.5 3 t(seconds) Newtons dynamics force audio force Figure 3: The dynamical force (blue) and the audio force (red) ....

D. D. Nelson, D. E. Johnson, and E. Cohen. Haptic rendering of surface-to-surface sculpted model interaction. In Proceedings of the ASME Dynamic Systems and Control Division, volume DSC-Vol. 67, pages 101--108, 1999.

....Cremer s Newton dynamic simulator. The provided example interactions are limited to relatively simple objects such as a cylinder rolling on a block without slipping and a torus rolling on a plane. An alternate version of the contact kinematics equations is derived by Nelson Johnson and Cohen in [35]. They use a separation distance as one of their contact coordinates allowing them to easily measure penetration distance during contact evolution. In this paper the penetration distance is used to compute a contact force in a haptic simulation of NURBS surfaces in contact. 2.3 Smooth Surface ....

....is often the most computationally expensive component of physically based simulations. Collision detection can be minimized or even omitted if we know that the object shapes do not allow multiple contacts. 18 Additionally, single contact can be useful in a variety of situations, such as haptics, [35], and certain manipulation examples, 22] Fast contact evolution is interesting for real time interaction with smooth objects where contact evolution information is used for sound synthesis, 13, 14] 19 Chapter 4 Formulation 4.1 Preliminaries In this thesis we use a notation for spatial ....

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D. D. Nelson, D. E. Johnson, and E. Cohen. Haptic rendering of surfaceto -surface sculpted model interaction. In Proceedings of the ASME Dynamic Systems and Control Division, volume DSC-Vol. 67, pages 101--108, 1999. 83

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D. Nelson, D. Johnson, and E. Cohen, "Haptic rendering of surface-to-surface sculpted model interaction," in Symposium on Haptic Interfaces for Virtual Environments and Teleoperator Systems (HAPTICS 1999.

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Nelson, D., Johnson, D., and Cohen, E., "Haptic Rendering of Surface-to-Surface Sculpted Model Interaction," in Proc. 8th Annual Symp. on Haptic Interfaces for Virtual Environment and Teleoperator Systems, (Nashville, TN), ASME, November 1999.

....examined and the number of edges drawn. By using variable precision silhouettes, models can render in time sub linear to the number of actual silhouette edges. On large models, this can result in substantial speed ups. This technique also matches well with artistic rendering methods, such as [17], that do a post process on the silhouette edges to produce a drawn look. 4.2 Local minimum distance In the previous section, we applied spatialized normal cone hierarchies to a much studied area, silhouettes, and demonstrated extending standard silhouette extraction to extract variable ....

....the local minima as well, as in Figure 11. ################ Figure 11: The local minimum distance returns more information about the distance between models than the global minimum distance. This project was motivated by the need for a predictive contact algorithm in a haptic rendering system [17]. The haptic system needed to initialize local tracking methods in order to provide high response feedback. A global method will only report on one location, possibly missing other nearby regions of interest. Additionally, a simple modification to a global algorithm to return all pairs of ....

#Nelson, D., Johnson, D., and Cohen, E., Haptic Rendering of Surface-to-Surface Sculpted Model Interaction, in Proc. 8th Annual Symp. on Haptic Interfaces for Virtual Environment and Teleoperator Systems, (Nashville, TN), ASME, November 1999.

....model configuration. The zero distance constraint in this case is called extremal distance, as opposed to minimal distance, because f and g may be interpenetrating. The extremal distance contact points have been studied with gradient descent [34] and improved Newton iterative distance approaches [18, 28]. The velocity formulation of Eq. 4 guarantees the maintenance of the extremal distance solution since it is an exact computation, not an iterative numerical method, and cannot not slide into extraneous, undesirable solutions. If there is an extremal distance solution, the velocity method will ....

....through a combined local and global tracking process. We have implemented a three step tracking process to manage the global issues that are not guaranteed by the local collision methods. The details were reported in previously as part of results on a haptics surface surface tracing algorithm [28]. Our Figure 4: Unsatisfied surface surface contact constraint showing minimal distance between the surfaces and surface curve minimal distance. Several constraint domains to write the surface curve inequality condition are possible. manager uses a global polygonal collision algorithm [21] on an ....

Nelson, D., Johnson, D., Cohen, E., "Haptic Rendering of Surface-to-Surface Sculpted Model Interaction," to appear, Symp. on Haptic Interfaces, ASME International Mechanical Engineering Congress and Exposition, Nashville, TN, Nov. 1520, 1999.

....surface oriented approaches since the models contain no topological adjacency information. The method requires tracking a closest point on each proximal surface to allow tracing across surface boundaries. This in turn limits both the complexity and number of models populating the environment. Nelson et al. 1999) provide a closed form solution in the velocity domain for tracing sculptured NURBS models using a locally convex end effector model. While this method allows the end effector to be sculptured, the contact model is a single point and the approach is surface oriented with no transitioning ....

Nelson, D., Johnson, D., Cohen, E., 1999, "Haptic Rendering of Surface-to-Surface Sculpted Model Interaction," in 8th Annual Symp. Haptic Interfaces for Virtual Environment and Teleoperator Systems, Nashville, TN.

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