Credits: Many of these notes were culled from the IEEE VR '99 Tutorial "The Art and Science of 3D Interaction" by Doug Bowman, Ernst Kruijff, Joseph LaViola, and Ivan Poupyrev

Outline

• OpenGL Lighting Tips
• Interaction Modes for Interactive Graphics
• Interaction Techniques for VR
• Selection
• Manipulation
• Menus
• Navigation
• VR Interaction - Myths & Realities

OpenGL Lighting Tips

• specify light light position (x,y,z,w)
• w = 0 -> infinite light
• w = 1 -> local light
• glLightfv(GL_LIGHT0, GL_POSITION, lightPos);
• bind light position before CAVENavTransform for light fixed to CAVE, after for light fixed to environment.

Interaction Modes for Interactive Graphics

• Logical Classification of Input Devices (Hearn & Baker)

• locator - specify position
• stroke - series of pos
• string - text input
• valuator - scalar values
• choice  - menu
• pick - select picture elements
• also add:  orienter

• Input Modes (Hearn & Baker)
• request mode - app blocks until input is received
• sample mode - "current values" of input device are stored in common area, sampled as needed; VR & head-tracked graphics
• event mode - all desired values (events) are buffered and reacted to on a FIFO basis; non-head-tracked graphics (e.g. GLUT)

Selection

Selection Techniques

• virtual hand (touching)
• hand (wand) intersects object
• ray casting
• simple laser
• flashlight (selection cone)
• aperture (variable cone)
• gaze-directed ray casting
• go-go technique
• 1-to-1 virtual hand movement within radius r
• non-linear mapping outside of radius r
• image plane techniques
• variation of ray casting
• world in miniature (WIM)
• "hand-held" version of world for simple picking
• scaled world variation shrinks the world when an object is selected
• cyclic selection
• selection from menu

 

Other Selection Issues:

• how to invoke - button press, gesture, voice command
• feedback - graphical, audio, haptic

Manipulation

Manipulation Techniques

• direct manipulation (virtual hand) - object and hand share the same center of rotation; direct mapping of hand changes to wand changes
• "object on a stick" manipulation (ray casting) - object and hand share the same center of rotation; however, object translation away from center magnifies changes in position via orientation. (translate, then rotate)
• remote manipulation (ray casting) - object rotates relative to its own center of rotation. (rotate, then translate)
• "fishing reel" (ray casting) - easy way to control distance of object
• decoupled orientation and positioning
•  object may fly to hand for orientation.
• menu control of each parameter (x, y, z position; x, y, z rotation)
• direct manipulation in WIM - translations are magnified to world scale
• direct manipulation in scaled world

Other Manipulation Issues:

• constraints on maniuplation
• snap to grid
• orientation increments
• how to release:
• final location of object (for WIM & scaled world methods)

Menus

General Problems with Menus in VR

• limited number of buttons
• limited resolution and screen real estate (esp. HMD)
• tracker jitter and latency
• fine motor (desktop) vs. gross motor (VR)

Menu Techniques/Widgets

• 1 DOF
• ring menu

• linear menu
• rotary chooser (sundial, marking menu)
•  2 DOF
• traditional 2D menus
• pull-down, pop-up
• toolchest or toolbar
• widgets
• buttons & sliders
• pen & tablet interaction
• transparent plexiglass panel for projection VR
• glove-based gestures
• voice input

Navigation

Wayfinding Techniques

• structured space - consistent; hierarchical
• landmarks and grids
• supplementary maps, WIMS - exocentric view

Travel Techniques

General Issues

• start moving
• specify position
• specify orientation
• control speed and acceleration
• stop moving

Travel Metaphors

• Steering - continuous specification o fdirection of motion
•  gaze-directed
• pointing
• physical device (steering wheel, flight stick)
• Target-based - discrete specifiation of goal; system controls the actual motion
• select object (see above list)
• enter coordinates
• Route-planning - one-time specification of path
• place markers in world
• move icon on map or in WIM
• Manual manipulation of viewpoint
• "camera in hand" (with WIM)

VR Interaction - Myths and Realities

Myth: interaction techniques should strictly imitate real-world manipulation
Reality: only if the goal is training for real-world performance; unnatural or magic techiques have many desirable characteristics

Myth: We should develop universal interaction techniques
Reality: optimal techniques depends on the task, the environment, the hardware affordances, and the user

Myth: interaction techniques should be 6 DOF
Reality: Constraints on position and orientation can make tasks much easier