The Complete Guide to Blender Graphics
Path Animation

Path Animation

Objects may be animated to follow a “Path” by constraining them to a “Curve”. A “Path” may be any of the “Curve” options available from the “Add – Curve” selection menu.

To demonstrate, deselect the “Cube” object in the default Blender scene. Place the 3d window in “Top Orthographic” view. Add a “Curve – Bezier Circle” and scale the circle up as shown in the diagram.

Scale the “Cube” object down while it is at the centre of the scene. With the “Cube” selected add a “Follow Path – Object Constraint”, check “Follow Curve” in the constraint panel and set the “Target” as “BezierCircle”. The “Cube” will relocate to a position on the “Curve”. Deselect the “Cube”.

Select the “Bezier Circle”. In the “Properties” window, “Object data” buttons, “Path Animation” tab ensure “Path Animation” is checked. Note the “Frames: 100” and “Evaluation Time: 0.000” entries. For the time being leave these default values.

In the “Timeline” window you will observe that a 250 frame animation is set by default. The animation is set to start at Frame:1 and end at Frame 250. The “Timeline” cursor (Green Line) is located at Frame 1. If the “Frame Rate” in the “Properties” window, “Render” buttons, “Dimensions” tab is set at 25 frames per second this will produce an animation lasting 10 seconds.

To animate the “Cube” to traverse around the circular path “Keyframes” have to be inserted in the “Timeline”.

To insert “Keyframes” go to the “Path Animation” tab in the “Properties” window. With the “Timeline” window cursor positioned at Frame 1, Right click on the “Evaluation Time” bar and select “Insert Keyframe” from the menu that displays. Note that the “Evaluation Time” value at Frame 1 is 0.000.

The “Evaluation Time” bar turns yellow indicating that a keyframe has been inserted and a short vertical yellow line in the “Timeline” window at Frame 1 confirms this.

Note: The “Frames” value in the “Path Animation” tab does not indicate a position in the “Timeline” window or the length of the animation. It states that the animation path (The Bezier Circle) is divided into 100 divisions.

Reposition the “Timeline” cursor at Frame 200. Change the “Evaluation Time” value in the “Path Animation” tab to 100. Right click on the “Evaluation Time” bar and select “Insert Keyframe. A second vertical yellow line is entered in the “Timeline” at Frame 200.

OK. What has happened?

In the “Path Animation” tab the “Frames: 100” value states that the “Curve Path” (Bezier Circle) is divided into 100 divisions. Division 1 is at Frame 1 in the “Timeline”. Division 100 is at Frame 200 in the “Timeline”. With the “Evaluation Time” set at 100 at Frame 200 the “Cube” travels around the complete path between Frame 1 and Frame 200 in the “Timeline”.

Note that the traversing speed is not constant. If you open the “Graph Editor” window you will see that an F-Curve has been created which has acceleration and deceleration at the ends of the curve. Handles have been placed on the curve at the “Keyframe” locations

Go back to the “Timeline” window and position the cursor at Frame 110. Change the “Evaluation Time” to 25. Right click and insert a new Keyframe.

When the animation is replayed the “Cube” traverses the path one quarter of the way around the circle between Frame 1 and Frame 110. It then speed up and continues on completing a full circle at Frame 200. The “Cube” stops while the animation continues to play on to Frame 250.

If you add a “UV Sphere” to the scene and position it to one side of the screen then insert a “Keyframe” at frame 1 ( Press the I Key, select Location) then move it to the opposite side of the screen and insert a “Location” Keyframe at Frame 250 you will observe the “Cube” traversing around the circle between Frame 1 and frame 200 while the “UV Sphere” moves from one side of the screen to the other between Frame 1 and Frame 250.

This demonstrates that the speed of movement and position of objects in the scene can be controlled by “Path Animation”. When used in conjunction with the “F-Curve” in the “Graph Editor” window a very versatile control is made available.

Note: Inserting Keyframes adds handles to the F-Curve which may be moved to effect movement.  

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