Sensors and Triggers

• 21 Sept: Changed Trigger:action from SFString to MFString

Goals

Overview

1. Sensors: These provide a way to detect a condition, the two nodes shown detect a persons viewpoint being within a region, and detect the picking of an object (clicking a mouse on it).
2. Connectors or Triggers: These link the output of a Sensor, or some other variable, to an action.

This proposal is intended to catch the 80% set of trivial behaviors, allowing the remaining 20% to be covered by more complex behavior nodes, as described in vrml-behaviors.html.

Dependencies

Sensors

RegionSensor

reports when the viewer's camera position enters, exits, and moves inside (or outside) its target region.

RegionSensor {
    bboxCenter          # as per WWWInline, defines spatial target region
    bboxSize
    target  NODENAME    # or reference geometry to be used as spatial target
    sense   NODENAME    # node whose position is checked; default is camera
    isIn                # TRUE while camera position remains inside region
                                                # This field is a READ interface, allowing it to be 
                                                # tested elsewhere.
    {}                  # child geometry is traversed for rendering
}

PickSensor

reports when the viewer picks a node (e.g. user clicks Left Mouse Button over)

PickSensor {
    target  ""        # SFString - node name reference to geometry to be picked
     picked  FALSE    # SFBool - true when picked
     prePick FALSE    # True when mouse over this sensor (but not clicked)
    {}                # child geometry is traversed for rendering
}

Connection and Trigger

Connection { 
    from  ""            # SFString Field Name of field to be tested
    to    ""            # SFString field name of field to update
}                             

    DEF DoorPad RegionSensor {
        bbox ~~~~~~     # define a volume above the doormat for sensing
        Separator {
            # draw a picture of the doormat here
        }
    }
    DEF MyDoor SwingDoor {
        # draw door frame here
        isA Separator
        fields [ SFBool READWRITE doorOpen ]
        doorOpen FALSE
        Switch {
            whichChild USE MyDoor.doorOpen
            Separator { 
                RotationXYZ { axis Y angle 0 }
                DEF DoorBody Separator {   # Draw door here }         
  
            }
            Separator { 
                RotationXYZ { axis Y angle 1.5708 }
                USE DoorBody 
            }
        }
    }

    Connection {
        from DoorPad.isIn               # connect value of isIn field
        to MyDoor.doorOpen
    }

Trigger couples an event (e.g. a sensor event) with an action

Trigger {
    condition ""                # SFString - Fieldname to watch 
    action ""                   # MFString
}

• an author could use the following instead of an WWWAnchor:

      DEF MyAnchor PickSensor {
          sense USE Door
      }
      Trigger {
          condition MyAnchor.picked
          action "open http://~~~~"               # open new .wrl
      }
  

• alternatively the connection above could be phrased as:

      Trigger {
          condition "DoorPad.isIn"
          action "set MyDoor.doorOpen = 1"
      }
  

• This allows a future for logic syntax such as:

      Trigger {
          condition "DoorPad.isIn && keyLock.isIn"
          action "set MyDoor.doorOpen = 1"
      }
  

Actions

A first cut would allow the trigger to:

• Set a field,e.g.

  "set MyDoor.doorOpen = 1"

• Load a URL and replace existing geometry with it, e.g.

   "load http://foo.com/newroom.wrl"

• Trigger a behavior, e.g.

  "set MyDoor.openbehavior.running = 1"