Living creatures avoid sudden changes in speed or direction of movement. Abrupt changes in motion require much more force to be applied, and such movements can be traumatic.
Rapid changes in angular momentum can create a large force of inertia, which can make it difficult to control movement
Therefore, living things move in such a way as to continually smooth out sudden changes in angular momentum or acceleration a little bit.
For example, when walking or running, people may swing their arms. The position of the arms affects the position of the center of mass. Thus, through arm movements, people make smoother transitions from one fulcrum (" foot ") to another, controlling the angular momentum during each step.
The compensation tool allows the animator to add small compensating movements to smooth out speed and angular momentum in the animation, while still maintaining the main movement.
The compensation tool can work with rotation. Let's see how it looks like on a simple example:
- Download and open a scene for the rotation compensation test.
- Turn on auto physics
- Turn off the physics corrector filter. It has already been applied for this scene!
- Turn on the compensation filter
- Set Rotation cut off to 0
In order for the filter to work, you must also assign the points that the tool will use.
- Go to the Point Controllers mode.
- Double click on the character's stomach point to select the entire upper body.
- Select all frames of the animation and enable the Apply on selected interval button
- Open the Compensation motion tab and set Muscle stiffness to 10 for the selected points.
- Play the animation
So what exactly did the tool do in the example above?
We can see how on the physical assistant the body rotation starts a little earlier, then the body starts lagging behind, and eventually the body rotation slowly stops already after the character lands.
In the original animation, the character stands still and then turns around abruptly. You can see how quickly the angular momentum changes! (you can enable angular momentum display in the view mode settings)
Literally in one frame the angular momentum arrow increases from zero and reaches half a circle! In real life such a motion would be almost impossible.
Now let's look at the moment of inertia in the animation after applying physical adjustments!
The angular moment arrow smoothly increases and smoothly decreases at the end of the motion!
This is the angular momentum smoothing!
In order to control the compensation effect for rotation (i.e. for the change in angular momentum) you can change the Rotation cut off value
A value of 0 means that at each next simulation step (in each next frame) the tool will require zero torque forces.
This will produce the most noticeable changes!
You can also set only partial rotation compensation.
The closer the Rotation cut off value is to 100, the less the animation will deviate from the original.
When Rotation cut off = 100, the tool is considered to be off.
By selecting different points and adjusting the Muscle stiffness value for them, you can control which parts of the body will be used to smooth the rotation.
Muscle stiffness = 100 means that these points will completely follow the original animation.
The closer the value is to 0, the more freedom there will be for this part of the body, and the more this part will be involved in rotation compensation.
There is no universal recipe for setting points in this case. It all depends on your goals in each particular animation.
For example, I have the animation of a red panda.
The movements of the main body parts are made by reference with human actors.
But I do not know how the tail of the animal should behave. In this animation, it just remains not animated yet.
However, tails often play a very important role in animal movement, many animals use them for balance.
In this case, I can try to compensate for the rotation just by tail points. In this way, the tool will guide me to the positions for the tail!
