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3D Mechanics

spinning barbel tracing a helical path

Software for Simulating the Dynamics and Statics of Structures

3D Mechanics allows you to assemble virtually any three-dimensional structure by attaching connecting rods to point masses. You may then apply forces to these masses and simulate the subsequent motion of the entire object. It is not the intention of 3D Mechanics to directly answer any question about the motion of physical objects. Its purpose is instead to supply the position, velocity, and force information you need to figure out for yourself what is going on.


Geodesic dome compressed under gravitational loads
Figure 1. Architectural model of a geodesic dome subject to gravitational loads.

The dome consists of a lattice of magenta masses held together by massless rods. The rods are elastic and are tinted green in proportion to the amount they compress. Note how evenly the loads distribute themselves through the structure.
Standing wave on a string
Figure 2. A standing wave on a string.

Here a string is simulated using a series of closely-spaced point masses joined by rigid massless connectors. The cyan vectors indicate the velocity of each masslet while the blue dot shows the position of the center of mass of the entire string.

The program relies only on basic concepts like force, mass, acceleration, and velocity to simulate motion. When results regarding more advanced concepts such as center of mass motion and conservation theorems emerge from simulations, they are more believable because they are not directly built into the program.

Velocities and forces may be manipulated either with the mouse or by using dialog boxes in which each vector is described using both cartesian and polar coordinates.

Individual masses can leave behind markers to show past positions. A user may shift the viewpoint and may even attach it to a moving mass. Time may be either run continuously forward or advanced and retarded instant by instant.

Both elastic and rigid bodies may be modeled. If the external forces applied to a rigid body are momentary ones, such as occurs when we give an object a short push, the program can show how the motion of the body develops in the first instants after the forces have acted. We may watch as the point masses in the body are displaced and momentarily stretch or compress the connectors to which they are attached. As the connectors snap back to their original lengths they drag the attached masses with them and thus impart velocity to these masses. By observing the development of these velocities as the structure regains its former shape we can understand the motion after the external forces have ceased to act.

Topics 3D Mechanics can help explain include:

Or it may be used simply for having fun.



Download the Free Trial Version

After verifying that your computer satisfies the system requirements, download the trial version of 3D Mechanics. This version lacks only the ability to save simulations.

Order the Complete Program

If you find the trial version useful, for $25 you can then register the program and restore it to full functionality. Payment can be made in a wide variety of currencies using all major credit cards, checks, cash, and money orders. Orders made over the Internet are safe due to the high degree of order security employed by the company which handles the financial transactions. All orders are subject to a liberal refund policy. Personal information needed to complete the order such as email and postal addresses will be kept private. Any questions regarding orders or the program itself may be emailed to Twilight Software.