This is the name of two common phenomena in the MMD Community.
1. Putting extremely long intros on MMD videos for an extremely short clip. It is a pet peeve for the community.
2. Fans downloading the program and not knowing what to do. This section deals with #2.
Basic Frame Register
MMD is based on the Frame Register method of animation. In order to move a model, you must move the bones to a certain position, and click Register. The same applies as well for Facial Features and Model Display functions. Move ahead a few frames and move the model into the next position, Register, and you've got an animation!
The interpolation curve determines the movement that occurs in each frame between two registered frames. Only the interpolation curve at the second(end) frame matters.
It can be thought of as a chart which controls movement over time. The left and right of the chart are the beginning and end of the animation represented by the two frames. The line's height at any point represents the progress of the animation at that time. You can think of this as a general rule: The flatter the interpolation line is at any point on the chart, the less movement there is at the corresponding point in the animation.
The interpolation line is possibly MMD's most powerful animation tool, as it is the only method of animating at accuracies greater than 30FPS.
1. If the line is straight, the animation (movement) created by the two frames will be distributed evenly throughout every frame in between.
1. If the line is flat at the bottom in the middle of the chart, there will be essentially no movement even halfway into the animation.
2.if the line is flat at the top in the middle of the chart, the animation will finish halfway between the two frames.
3. Is the line is in an S curve, arguably the most common and useful type of curve, the animation will start slow, accelerate, decelerate, and then finish.
Many people may find their motions improve significantly just by putting light S curves throughout the animation. But the proper use of the interpolation line requires an understanding of how it actually works so that you can tailor the curve to the nature and context of the motion you're trying to create. There is no one all-purpose interpolation curve.