1. 1 Haptic Systems 530-655 Mohsen Mahvash Lecture 6 17/1/06

2. 2  The god-object method  A simple collision detection method  Sliding contact  Spherical proxy  Improving collision detection algorithms  References Haptic rendering of contact

3. 3 Haptic simulation of contact with a virtual wall god object proxy contact point

4. 4 A physics-based method The tip of a virtual tool comes into a contact with a stiff deformable body at point c and then the contact point slides over the surface of the virtual object

5. 5 The god-object method The god -object is moved to a point that locally minimizes the distance between the god-object and the tip of the haptic device, subject to a surface constraint. (equation of a plane)

6. 6 Surface representation of 3D objects Many complex objects can be represented by triangles.

7. 7 A simple collision detection method Points and define a line segment. For a triangle that collides: Determining the triangles which collide with the line segment.

8. 8 Sliding contact (convex objects)

9. 9 Sliding contact (concave objects) Several surface constraints are active when the god object crosses an edge of a concave surface.

10. 10 An optimization problem

11. 11 Spherical proxy object surface configuration space obstacle proxy Falling through holes of a virtual object can be avoided by using a spherical proxy

12. 12 Improving collision detection algorithms OBBTrees Method: an oriented bounding box surrounds all objects under a subtree. If the line segment does not collide with the box it will not collide with the objects inside the box.

13. 13 Tomorrow Force shading and rendering of friction References: 1.C.B. Zilles, J.K. Salisbury, A constraint-based god-object method for haptic display International Conference on Intelligent Robots and Systems-Volume 3. 1995. 2.D. C. Ruspini, K Kolarov, O Khatib - The haptic display of complex graphical environments, SIGGRAPH, 1997. 3.A Gregory, M Lin, S Gottschalk, R Taylor, H-collide: A framework for fast and accurate collision detection for haptic interaction Proceedings of IEEE Virtual Reality Conference, 1999.