Audrey St. John

3D Body-and-Bar/Hinge Pebble Game Demo

This applet demonstrates the (6,6)-pebble game used to solve the decision, spanning, extraction, optimization, components, redundancy, and Henneberg problems for 3D body-and-bar rigidity.

You may also be interested in the pebble game for 2D bar-and-joint rigidity.


  • Use the standard play controls at the top to play the pebble game (animate, step individually or "fast forward" to the end); this will cause edges to be inserted in arbitrary order.
  • To insert edges one at a time in a specific order, do not press the play controls after initializing the graph; instead, simply click the edges in the left pane as you want them inserted. The play controls will become available once the first edge has been chosen.
  • Use the View menu to change the moves displayed for the game:
    • Show all moves will show every move the game makes, including pebble searches and edge reversals.
    • Show only one move per edge iteration will only show the outcome of each edge consideration (rejection or acceptance).
    • Show only final configuration will only show the final outcome of the game.
  • To load a predefined graph, select from Graphs menu
  • To create a graph
    • Go to the Create graph tab
    • Add vertices by right clicking and selecting "Insert"
    • Add edges by clicking first vertex (hover over center until you see a hand cursor, then click), then pull to second vertex
    • Adjust radius by selecting vertex and pulling bounding box
    • When finished, click "Set graph" button at the bottom
    • Return to Play pebble game tab to run pebble game algorithm.

Advanced usage

To run the demo locally on your machine (allowing the additional feature of file saving/loading), simply download pebblegame.jar and double-click it to run.