Graphics Programs Reference
In-Depth Information
After reshaping the path, press Alt + the A key to see the cube move along the path. For
the cube to follow the path with its axis aligned to the path, you must have “Follow” ticked
in the
properties window - “Path Animation” tab.
Shaping the path gets the cube moving
around in the scene, but it moves along the path at a constant speed. In real life, if the cube
came to a sharp corner without slowing down, it undoubtedly would suffer an accident. To
create a realistic movement, we need to vary the speed.
Varying the speed is performed in the graph editor window. It helps at this stage if you
have both the graph editor window and the 3D window displayed at the same time. Divide
the 3D window in two horizontally and change one half to the graph editor window. You
will probably have to zoom in on the graph editor window and pan the window into posi-
tion. At this point, all we have is the red line showing a constant velocity and unfortunately
the line is uneditable. The horizontal and vertical green lines are cursor lines; the vertical
line is a cursor for positioning along the horizontal timeline measured in frames of the
animation, and the horizontal line positions on the vertical displacement scale measured
in Blender units.
On the LHS of the graph editor, you will see the dope sheet panel. With the path selected
in the 3D window, the dope sheet shows information associated with the path. Click on the
lower white arrow at the LHS of the panel and a channel will display labeled “Evaluation
Time.” Clicking on the eyeball at the LHS of the channel toggles the display of the red line
on and of. Clicking on the little speaker icon at the RHS of the channel toggles between
selection and deselection of the channel.
The channel in the dope sheet panel is a graphical representation of information associ-
ated with the display in the “Evaluation Time” button in the properties widow - “Object
Data” button - “Path Animation” tab (the green bar). The same information is displayed as
the red line in the graph editor window.
So what is this “Evaluation Time” business? Let's evaluate what we have at this stage.
In the 3D window, we have a cube object parented to a curve path. Blender has set the
cube to traverse the path in 100 frames of the animation—this happens to be the first
100 frames of the animation. In the timeline window at the bottom of the screen, the
total animation is set at 250 frames starting at frame number 1 and ending at frame 250
(Figure 9.36). Playing the animation shows the cube moving along the path starting at
frame 1 and reaching the end of the path at frame 100. The animation continues to play
on to frame 250.
Figure 9.36
In the properties window - “Object Data” button - “Path Animation” tab (with the path
selected in the 3D window) “Frames: 100” is the number of frames to traverse the path.
“Evaluation Time: 1.000” is where the cube is located on the path at frame 1. Increasing the
