Non-Linear Animation: Animating with the Trax Editor in Maya 4.5 and 5
By Brian J. Immel
Layers of Non-Linear Animation
Blending Clips
Blend Clips allows for smooth transitions from one Clip to the next.
How to blend Clips
- Select only two Clips
- Go to Create > Blend or right click on the selected Clips and select Blend Clips.
- Maya will create a wire connecting the end of the first Clip to the beginning of the second Clip.
- Depending on how much overlap, Maya will create a smooth and seamless blend between Clips. Example: if I have a walk cycle blend into a run cycle, I will want to overlap at least the last three frames of the walk cycle with the first three frames of the run cycle. So if my walk cycle ends on frame 17, I will move the run cycle to start on frame 14 and create a blend from there.
- Also, depending on the cycles of the Clips, the blend may not be as seamless as we would hope for. In the fore-mentioned example, if my walk cycle starts and ends on the left foot and the run cycle starts and ends on the right foot, then my blend would not look to great. I would need to loop the run cycle one and a half times, split the run cycle where the left foot starts the loop and then create the blend from there.
Types of blending
- Linear
- Ease In
- Ease Out
- Ease In and Ease Out
- Custom
If you select the wire that connects the two Clips, you can edit it in the Graph Editor. - Each type of blending methods will result in different looks to how the Clips blend together. I can’t suggest a good or right one for your Clips. All I can say is experiment!
Clips on top Clips (layered Clips)
Sometimes it makes sense to layer your animations by separating the arm movement from the legs, torso, head and hands. Case in point, you can create a walk cycle, Clip out the feet, arms, hands, torso and head motions separately. Then build a short animation of the arms waving like a prom queen and mix together the Clips of the feet, and torso with the Clip of the prom queen to get a whole new motion. And for good measure, we could through in a motion or two of the prom queen thanking the crowd with kisses.
Be careful if you planning on layering Clips. If you layer two Clips that involve data on the same attributes (like the feet for example), then you will get a very messy motion. It’s quite possible that you character will look like it’s trying to rip itself apart.
Adding keyframes on top of Clips (Motion Warping)
You can add keyframes on top of animation from a Clip. To do this, just keyframe as you normally would keeping mind the following items:
- You shouldn’t add keyframes to an attribute is already driven by the Clip data. You can but just be mindful that this has the potential for messy animation.
- It may be necessary (depending on the motion) to turn the Clip’s data to Relative instead of the default setting of Absolute. To do this, select the Clip and right click on it selecting the Attribute Editor option. In the Attribute Editor, go to the section labeled Offset. Select Relative and make sure that the Clip is set to Enable.
Case in point: stationary walk cycle with forward motion via keyframes.
Exercise: Motion Warping
1. Open the file run cycle.mb.
2. Select the MoveMe node around Oscar’s waist (the 4 pointed star) and the two feet controls.
3. Set a keyframe on Translate Z at frame 1.
4. Move the playback head to frame 64.
5. Move Oscar’s MoveMe and feet controls to a value of 60 or so. This will set up a linear motion that will come close to the running pace in the clip but will still look a bit off.
6. Set some inbetweens so the body and feet have an easing-in and easing-out motion during the run cycle. The inbetweens should look something like the illustration below. Continue tweaking the Translate Z keys until you get just what you want.
