Starting point for this tutorial.
Moho's bone dynamics system can be used to automatically move bones around in response to higher-level movement. Moho uses a physical simulation of springs to calculate dynamic bone movement, making it suitable for a wide range of movements, such as flabby body parts, bouncy hair, waving arms, etc.
For this tutorial, we'll start with a project file that's almost finished. It's named "Tutorial 3.3" and it's located in the "Tutorials/3 - Bones" subfolder within the main Moho folder. Open this file in Moho, and you should see something like this:
Starting point for this tutorial.
Play back the animation to see what we're starting with. The entire structure will tilt side to side and bounce up and down, remaining rigid the whole time. Only the vertical bone in the center of the skeleton is animated - all the others move with it because they are its descendants. Rewind the animation to frame 0 when you've seen enough.
Use the Select Bone tool to select the top-left bone in the structure as shown below:
Select this bone.
In the tool options area at the top of the main Moho window, click the "Bone constraints" popup box to open it. In the popup box, turn on the "Bone dynamics" check box. This tells Moho to move the selected bone automatically according to the spring simulation.
Turn on bone dynamics.
Select seven more bones (two in each of the "arms"), and turn on bone dynamics for each one. Here's a tip: you can leave the "Bone constraints" popup box open the whole time, just click on each bone in turn, then turn on bone dynamics for each one. If the "Bone constraints" popup box covers up some of the bones, you can pan the editing view by dragging with the right mouse button to expose the hidden bones.
At this point, you should have turned on bone dynamics for every bone in the structure except the vertical center bone. Play back the animation to see the difference. Now as the structure tilts side to side, the "arms" will bounce around in response to the movement of the center bone.
So that shows the basics of how to use bone dynamics. Now let's take a look at how you can make adjustments to the "bounciness" of the springs. Select the top-left bone again, and re-open the "Bone constraints" popup box. Below the "Bone dynamics" checkbox are three parameters that allow you to fine-tune the effect. Set the Torque force to 4, Spring force to 2, and Damping force to 2, as shown below:
Adjusting dynamics parameters.
A higher Torque force means that a bone moves more in response to its parent's movement, Spring force determines how quickly it bounces back, and Damping force controls how quickly a dynamic bone stops moving (you can think of damping like friction). In this case, a high torque force means that the bone will move more strongly. Select the bone's immediate parent (the second bone in the top-left arm), and apply the same dynamics parameters.
Next, select the two bones of the top-right arm (one at a time), and set the bone dynamics parameters to 2, 2, 5 (Torque, Spring, Damping). These settings will cause these bones to slow down their dynamic movement quickly - a high damping value is like making the bone move through a thick fluid.
Set a high damping force on these bones.
Finally, select the two bones of the bottom-left arm (one at a time), and set the bone dynamics parameters to 2, 4, 1 (Torque, Spring, Damping). The high spring force will cause this arm to bounce back very quickly.
Set a high spring force on these bones.
Try playing back the animation again. As you watch the final animation, note the differences between the four arms. The top-left arm swings in a wide arc because it has a strong response to the parent bone's movement. The top-right arm's movement is subdued because the damping force causes it to slow down more quickly. The bottom-left arm is very springy, and the bottom-right arm moves in accordance with the default bone dynamics settings.
The final result.