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UNC-Chapel Hill COMP 259 - Haptic Rendering

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Haptic RenderingWhat is haptics?What is haptic rendering?Why use haptics?Why use haptics? (2)Haptic ApplicationsHaptic Applications (2)Haptic Applications (3)Haptic Applications (4)Haptic interactionHuman hapticsHuman haptics (2)Human haptics (3)Human haptics (4)Haptic interfacesWhat makes a good interface?A good haptic interfaceA good haptic interface (2)Haptic renderingTwo types of interactionsTwo types of interactions (2)Collision detectionSimple collision responseSimple collision response (2)Penalty methodsPenalty methods (2)Penalty methods (3)Penalty methods (4)Solution? God-objectGod-object (2)God-object (3)God-object (4)God-object (5)God-object (6)God-object (7)Rendering surface detailsForce shadingSurface frictionHaptic texturingHaptic texturing (2)Haptic texturing (3)Challenges6-DOF haptics challengesExamplesReferencesReferences (2)The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Haptic RenderingMax SmolensCOMP 259March 26, 2003The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL What is haptics?•Using the sense of touch to interact with computers and virtual environmentsThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL What is haptic rendering?•The process of computing and generating forces in response to use interactions with virtual objectsThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Why use haptics?•Increases the information flow between the computer and the user•Intrinsically bilateral♦When we push on an object, it pushes back on usThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Why use haptics? (2)•Our sensing of forces is closely tied to our visual system and sense of three-dimensional space•Information and intent can be conveyed in a physically direct and primal wayThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Haptic Applications•Medicine♦Surgical simulators for training♦Manipulating robots for minimally invasive surgery♦Telemedicine, remote diagnosis♦Accessibility for the disabledThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Haptic Applications (2)•Entertainment♦Video games, simulators that enable the user to feel and manipulate objects in the environment•Education♦Feel phenomena at a variety of spatial and temporal scales♦Studying complex data setsThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Haptic Applications (3)•Industry♦CAD systems♦Virtual prototyping•Assembly and disassembly can guide final design♦Shape sculpting•Expressive, free-form shape generation and modificationThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Haptic Applications (4)•The arts♦Virtual painting, sculpting♦Virtual musical instrumentsThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Haptic interactionThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Human haptics•Mechanical, sensory, motor and cognitive components•Two classes of sensory information:♦Tactile♦KinestheticThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Human haptics (2)•Tactile information♦From skin in contact with an object♦Spatial and temporal variations of forces within the contact region♦Slipping, fine textures, small shapes, and softnessThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Human haptics (3)•Kinesthetic information♦Net forces along with position and motion of limbs♦Coarse properties of object♦Large shapes, spring-like compliancesThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Human haptics (4)•Kinesthetic resolution:♦2 degrees for fingers and wrist♦1 degree for shoulder•Force exerted by a finger:♦50 to 100 N maximum♦5-15 N typically during exploration and manipulationThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Haptic interfacesThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL What makes a good interface?•Must work with human abilities and limitations•Approximations of real-world haptic interactions determined by limits of human performanceThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL A good haptic interface•Free motion must feel free♦Low back-drive inertia and friction♦No motion constraints•Ergonomics and comfort♦Pain, discomfort and fatigue will detract from the experienceThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL A good haptic interface (2)•Suitable range, resolution and bandwidth♦User should not be able to go through rigid objects by exceeding force range♦No unintended vibrations♦Solid objects must feel stifThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Haptic rendering•Two parts: collision detection, responseThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Two types of interactions•Point-based haptic interactions♦Only end point of device, or haptic interface point (HIP), interacts with virtual object♦When moved, collision detection algorithm checks to see if the end point is inside the virtual object♦Depth calculated as distance between HIP and closest surface pointThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Two types of interactions (2)•Ray-based haptic interactions♦Probe of haptic device modeled as a line-segment whose orientation matters♦Can touch multiple objects simultaneously♦Torque interactionsThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Collision detection•Detect collisions between haptic probe and virtual objects•Bounding volume hierarchies, spatial partitioning•H-COLLIDE, hybrid technique:♦Partition virtual workspace as uniform grid♦For each grid cell containing primitives, computes OBBTreesThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Simple collision response•Haptic rendering of 3D sphereThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Simple collision response (2)•Reaction force calculated using the linear spring law F=kx♦k: stifness of object♦x: depth of penetration•Direction of force along surface normalThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Penalty methods•Subdivide object and associate each subvolume with a surface•Determine feedback force directly from penetration•Works well for simple geometric shapesThe UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Penalty methods (2)•There are some problems•Two possible paths to reach same location, which path was taken?The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Penalty methods (3)•Force summation for multiple objects•Compute net force by adding♦Correct for perpendicular surfaces♦For obtuse angle, force vector becomes too large♦When almost parallel, force vector too large by a factor of 2The UNIVERSITY of NORTH CAROLINA at CHAPEL HILL Penalty methods


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UNC-Chapel Hill COMP 259 - Haptic Rendering

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