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GBIC >> FreeWare >> gbAnimator >> Links
gbAnimator - Links
A link is simply the connection between two nodes. A link normally acts like a spring whose spring constant (stiffness) can be adjusted.

In addition a link can act as an Animator - a source of movement for the model. An animator can generate a push/pull force on the nodes attached to it - the equivalent to increasing or decreasing the length of the link. Links in gbAnimator have properties which may be set by the user:

1. Animator - a flag to tell gbAnimator to use the animator force and phase angle assigned to the link (see below). These two properties are ignored unless the animator flag is set.

2. Spring Constant (k) - stiffness of the link

3. Angle - the timing used to apply the animator force. The push/pull force of an animator is synchronized with the value of a sine wave applied to the elapsed time of the animation. That's a complicated way of simply saying that the force goes up and down - from a positive value (push) to a negative value (pull).

The time at which an animator starts its push/pull cycle can be adjusted by setting the angle (sometimes called the phase angle) property, with values from 0 to 360 degress. Animation of an entire model can be created by including several animator links in a model and adjusting the timing (angle) of the links.

4. Animator Force - all of gbAnimator's animation tools work by applying forces to masses. In the case of the link animator force, the property is a value from zero to one, which corresponds roughly to an effect of lengthening/shortening the link by the same percentage.

5. Barrier - a flag to tell gbAnimator to enable collisions between nodes and the link (still under development).

Nodes also have display properties - highlighted, selected and animated. A normal link, which is not selected or highlighted or animated is display as a black line.

When a mouse moves over the mid-point of a link, a white dot is displayed and the link is said to be highlighted. When the mouse moves off the link, the white dot will disappear, leaving behind just the normal black line.

Once a link is selected the white dot is replaced by a blue dot and the link color is changed to blue. To unselect a link, right-mouse click in an open area of the display.

To select a link you must click the mouse over the link mid-point.

To unselect a link, use a right mouse click.

As a convenience to identifying links whose animator flag is set, the toolbar button "Highlight Animated Links" may be used to display all animated links with a thick line.

The animator property of a link can be turned on by double-clicking on the mid-point of the link, or by using the toolbar button "Animation Enabled".