Another method of creating repeating sequences is by using Motion Clips. Although our example is very simple it can be used as a reference for the creation of far more complex sequences (e.g., the repetitive motion of a character’s walk cycle).
Begin by opening the following scene and selecting the Null Object at the top of the hierarchy:
Your Timeline should have automatically switched into Motion mode. Motion Clips can be repeated, cut, duplicated, scaled and blended. At the far left of the Timeline you can load (import) Motion Sources, which are animations that have already been converted to Motion Clips, from a preset library. Motion Clips can be exported to be saved as custom presets, for example, if you plan on using a certain Clip repeatedly. Motion Clip layers, located at the right of the window contaning the libraries, are especially useful for blending or replacing sequences without losing the original animation. The window in which the actual Motion Clips are displayed is where they can be positioned as desired. In the image below you will see that the Clip that was created lies at the same location and has the same length as the original animation. This is why you will not see a difference when the animation is played in its current state.
Now that the part of the animation to be repeated has been converted to a Motion Clip it can be positioned after the original animation. The animation itself ends at frame 120 so position the beginning of the Motion Clip at frame 120. Make sure the Motion Clip is selected and set Loops to 5.
Observe how the Motion Clip is displayed when looped. If the Motion Clip is selected the dark guide lines indicate where the Clip overlaps the original animation.
Set the total length of the scene to 305 (this can be done in the Powerslider) and play the animation. You will notice a very slight delay at the point at which the animation loops. This is due to the fact that the end and start images of the loop are identical and thus interrupt the smooth sequence of sequential images. This is very easy to correct when using Motion Clips. Select the Clip and set the Δ End parameter in the Attribute Manager’s Advanced tab to 1 (this will crop the last frame of the clip). Play the animation again and you will see that it now loops smoothly. Alternatively you could have omitted an image at the start or end of the Clip when creating it (e.g., by converting images 90 - 119instead of 90 - 120).
Click on the icon below to view the finished scene, which should match the result of your animation:
Why should Motion Clips be used instead of the Continue command? When using the Continue command, the Rotation value is increased permanently, which can lead to problems if, for example, this value is used to affect additional objects. The Motion Clip, on the other hand, always uses the values of the current sequence. It only rotates from 360° to 720°. This can often be very useful. For example, the modification of an animation’s F-Curves can be quite involved when working with complex hierarchies. Complex Motion Clips, however, are much easier to handle. The example we just demonstrated is very simple and Motion Clips can be used to handle much more complex animation processes.
This completes the introduction to animation with Motion Clips. Additional information and examples can be found in the MoGraph and XPresso chapters.