Node Properties

1. X position - set by positioning the node with the mouse

2. Y position - set by positioning the node with the mouse

3. Locked - set on the toolbar. locks the node in position during animation, but may be move manually by dragging with the mouse.

4. Mass - set on the toolbar (default value of 1). gbAnimator works by applying forces on nodes. Just as in real life, the greater the mass the slower velocity will build up.

5. Gravitational Force - a node can be assigned a gravitional force which will act on other nodes. Like real gravity, the force is inversely proportional to the distance to the other nodes. Unlike real gravity, which is proportional to the mass of the object, the mass property of a node is not used to determine the gravitional force it exerts on nearby nodes. in gbAnimator, mass of a node and it's gravitational force can be set independently of one another.

6. Rotational Force - a node can also be assigned a rotational force which will be applied to all connected nodes. The force is the same for all attached nodes (i.e., the force property is not divided by the number of attched nodes).

The rotational force is applied tangentially to the link connecting the nodes. A positive rotational force creates a clockwise rotation.

7. Initial X-Velocity - sometimes it's convenient to have a node start off with a velocity in a particular direction. The velocity applied to a node is divided into X- and Y- velocities.

8. Initial Y-Velocity - sometimes it's convenient to have a node start off with a velocity in a particular direction. The velocity applied to a node is divided into X- and Y- velocities.

During animation the XY position and XY velocities may change. When animation is stopped the position/velocity values are stored and used when animation is re-started (unless the model is manually reset to zero velocities). The model state is also stored when saved to a file.

In the real world a node would also have a physical size, but in gbAnimator a node is treated as a point mass. The display may show a finite dot size to represent the node, but all of the calculations assume the node exists at a single point and are not affected by the size of the display dot.

Display Properties
Nodes also have display properties - highlighted, selected, locked, and gravitional force status. A normal node, which is not selected, highlighted, not locked and with a zero gravitional force is displayed as a black dot (small circle). This default color may be changed by the user.

1. Highlighted - when a mouse moves over a node the black dot is replaced by an enlarged white dot and the node is said to be highlighted. When the mouse moves off the node, the white dot will disappear, to be replaced with a color reflecting the selected/locked/gravitational status of the node (see below).

2. Selected - once a node is selected the black dot is replaced by a red dot. To unselect a dot, right-mouse click in an open area of the display.

3. Locked - if a node is locked, the usual black dot (circle) is replaced with a small square.

4. Gravitional Force - if a node is assigned a non-zero gravitional force, the dot representing the node will contain a small yellow circle.