09: interactivity & animation

vrml event model

events and routes

• field stores a value (zzz)
• eventOut broadcasts a value (zzz_changed)
• eventIn receives a value (set_zzz)
• ROUTE connects eventIn TO eventOut
• exposedField combines eventIn, field, and eventOut
• if two field types match, a route can be established between them
  

  ROUTE TOUCH.isOver_changed TO LIGHT.set_on [»]

triggers and targets

• trigger -> target
  direct wiring (limits number of combinations, because event types must match)
• common triggers
  • ProximitySensor{}
  • TouchSensor{}
  • VisibilitySensor{}
  • Collision{}

  ROUTE NEAR.isActive_changed TO LIGHT.set_on [»]

• consider proximity and visibility sensors as opportunities to turn animations / objects / scripts on and off as needed, to reduce computational expense

interactivity

responsive environments

• input » user affects environment
• feedback » environment responds to user
• example [»]

instantaneous input

• booleans: isActive, isOver, isBound
• times: touchTime, enterTime, exitTime, collideTime, bindTime
• applications:
  • start a time sensor (initiate animation)
  • start a sound
  • activate / deactivate sensor nodes
  • flip on a light
  • bind new Viewpoint, Background, Fog, or NavigationInfo

continuous input

• xx_changed
• TimeSensor{} (interpolator fuel)
• TouchSensor{}
  • rollover [»]
  • sticky geometry [»]
• PlaneSensor{}
  • draggable letter [»]
  • 'magnetic' poetry [»]
• CylinderSensor{}
  • simple spinner [»]
• SphereSensor{}
  • bietler's joints [»]
• ProximitySensor{}
  • if the starting viewpoint is within the sensor, then enterTime = world.loadtime (useful trigger to start things when world loads)
  • size = 1e25 1e25 1e25 is large enough to house the observable universe, still smaller than largest valid float, 1e38
  • ninja! [»]
• sensor toy [»]

feedback loops

• perlin's walkers [»]

animation

binding nodes

• at most, only one of each active at any time
• all have set_bind event, to activate, deactivate others
• Viewpoint{}
• Background{}
• Fog{}
• NavigationInfo{}
• when animating viewpoints, consider starting animation at binding time, so not animating when view not active
  • shake [»]
  • elevator [»]

HUDs (Heads Up Displays)

ROUTE LOCATOR.position_changed TO HUD.set_translation
ROUTE LOCATOR.orientation_changed TO HUD.set_rotation [»]

timers

ROUTE TOUCH.touchTime_changed TO TIMER.set_startTime
ROUTE TIMER.fraction_changed TO LIGHT.set_intensity [»]

interpolators (engines)

• key frame animation: set a key (0..1), and specify a value for that key
• interpolators
  • ColorInterpolator{}
  • CoordinateInterpolator{}
  • OrientationInterpolator{}
  • PositionInterpolator{}
  • NormalInterpolator{}
  • ScalarInterpolator{} (good to modify TimeSensor.fraction_changed)
  • interpolator sampler [»]
• limit use of coordinate interpolation for better frame rates
• beware fast motion with tiny details; important frame may be dropped, so have more than one important frame

task05 [»]