Virtual Tinkertoys

This application allows a user to play with virtual tinkertoys in the C2 virtual environment. The C2 is a projection based device which surrounds the user with stereo computer graphics. For more information on the C2 and other VR devices here at ISU, see the ICEMT homepage.

In the tinkertoy environment, users can create two types of tinkertoys: sticks and disks. When a new object is created, it is automatically attached to the closest available point on the model. The user may reposition the new object as desired. Sticks and disks are implemented using C++ classes, so that a stick has a pointer to any disk attached to it, and disks have pointers to all attached sticks. In this way, the entire model is organized as a rooted tree, making operations such as collision detection easier.

The tinkertoy model has some motion capabilities. The user may manually choose to move pieces by rotating any disk in the model. Or the model may perform a random walk where disks are chosen at random and rotated.

The application runs well with a couple exceptions:

• Collision detection tends to cause the application to slow down when a large number of tinkertoys are present, resulting in a poor frame rate and loss of the sense of immersion in the virtual environment.
• An alternate version of the application allows to user to create sticks which are of variable lengths. However, the Vclip algorithm does not handle collision detection well if an object is resized after its creation.

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Computed Examples

The following examples are presented as QuickTime movies. Some may be up to 4.5MB in size.

The first example shows the user creating a new disk. It is automatically placed on the end of the existing stick. By turning his hand, the user may change the orientation of the disk so that a hole on the edge is used instead of the hole on the flat side.
• EXAMPLE 1: Create a disk

The second example shows the user creating a new stick. It is automatically placed in the closest hole of the closest existing disk. By moving his hand to a new location, the user may change the hole to which the stick is attached.
• EXAMPLE 2: Create a stick

The third example shows the user rotating an existing disk. As the user turns his hand, the disk also rotates. This movie is less smooth due to a low frame rate.
• EXAMPLE 3: Rotate a disk

The next example demonstrates the collision detection. As the user roates a disk, two sticks collide. They are drawn in red to indicate the collision. When the disk is rotated to that the sticks are not in collision, they are redrawn in green.
• EXAMPLE 4: Collision

The last example shows the tinkertoy model moving by itself. A disk is randomly chosen for rotation, a direction of rotation is randomly chosen, and a random number of degrees up to 360 is chosen. The model attempts to rotate the disk the specified number of degrees in the chosen direction. Then the process is repeated. However, if a collision occurs before the disk can be turned the desired number of degrees, the rotation is stopped and a new disk is chosen for rotation.
• EXAMPLE 5: Random walk

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Implementation Files

Source Code:

• Makefile
• main.C
• main.h
• model.C
• model.h
• disk.C
• disk.h
• stick.C
• stick.h
• stuff.C
• stuff.h

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arns@icemt.iastate.edu
last modified: Apr 29, 1999