Java Web Start: Launch the KineticModel by clicking here.
Download jar: Get the KineticModel jar file by clicking here.

This program models elastic collisions among spherical particles and the walls of a container. KineticModel uses the conservation of momentum [p = m·v] and kinetic energy [KE = ½·m·v2] to determine the velocity of particles after a collision. To simplify calculations, position and velocity are stored in 2-dimensional vectors as described below.


The design of KineticModel is an example of the Model-View-Controller pattern. The main class, KineticModel, creates an instance of the model, which is an Ensemble of Particle. It then creates the main view of that model, a DisplayPanel. A separate ControlPanel allows setting the simulation's parameters. The Vector class stores 2-dimensional vector data and provides elementary vector operations. Finally, a Histogram gives a continuously updated view of the Particles' velocities.


This implementation requires Java 1.5 or later. The animation loop is driven by a javax.swing.Timer instance in the controller. After an initial delay, the Timer fires at a nominal rate of 25 Hz, invoking the controller's actionPerformed() method. The latter repaints the main view, a histogram of particle velocities, and several informational labels. Three animation techniques are used: texture-paint, erase-draw, and label-icon.

In texture-paint animation, an instance of TexturePaint is created with a small BufferedImage. At each iteration, the image's raw pixels are randomly re-colored, and the TexturePaint is used to frame the view. Because the underlying image is small and used repeatedly for filling, the animation overhead is small.

The erase-draw method simply erases the entire panel to black, moves each particle to it's next position and re-draws the particle. The Particle may be filled with Color or drawn from a GradientImage The model's iterate() method handles collisions. Because the JPanel itself is double-buffered, the animation remains smooth.

Finally, the velocity histogram is repainted. The Histogram class simply extends JLabel and implements the icon interface, becoming its own icon.


Course material

Dr. David R. Gibson, Valdosta State University.

Revision history

1.2.0 15-Oct-2008 Use RadialGradientPaint.

1.1.0 01-Sep-2008 Initial release.

1.0.67 15-Jul-2008 Initial Java version.

KineticModel is an open-source project, distributed under the terms of the LGPL, version 3.

Copyright: ©2008, John B. Matthews.

Last updated 17-Oct-2008

Subpages (1): Source code
John Matthews,
Nov 20, 2009, 3:27 PM
John Matthews,
Apr 17, 2011, 1:22 PM