Bone Layers: Bone Mode

Bone mode is sort of a pre-animation phase. You don't draw shapes in Bone mode, but you don't animate either - you set up controls that will help you animate later on. The purpose of setting up bones is exactly what you might think: creating a rigid skeleton inside your drawing. Later on, during animation, when you want to move an object, bones make the job easy. By moving a single bone in the arm of a character, for example, the whole arm will move with it. Around the elbow, the drawing of the arm will bend and stay smooth (as long as the bones were set up well in the Bone editing mode).

Bone mode for a bone layer is where you actually create bones and attach them to one another. Bones by themselves don't really do much of anything: you can move them around, but they're invisible in the final Moho output. To really make use of bones, they need to be attached to objects in other layers. This process is covered in the Tutorials section, and also the chapters on Bone mode for other types of layers.

When you create a skeleton out of a group of bones, the bones have a hierarchy. Each bone has a single parent (or maybe no parent at all, in which case it's called a root bone), and each bone may have multiple children. The relationship between parent and children is that when a parent bone is moved, all of its children move with it. When a child bone is moved however, it's parent remains unchanged.

Below is a picture of a skeleton created in Moho. Green arrows have been added that point from each bone to its parent (the spine has no parent and is referred to as the root of the skeleton). Note that the currently selected bone is highlighted in red, and its parent (if it has one) is highlighted in blue.

Bone Tools

The following tools are available in Bone mode.

Select Bone
Using this tool, you can click on a bone to select it. You might want to select a bone in order to delete it (press the <delete> or <backspace> keys - all of its children will be deleted too). Click anywhere besides a bone to de-select all bones.

Add Bone
Use this tool to add new bones to a skeleton. The location you click will be the base of the bone (the point it rotates about), and where you drag to will be the endpoint. If another bone is selected before you click and drag, it will be the parent of the new bone you create. Otherwise, the new bone will be parentless, a root bone.

Hold the <shift> key to constrain the new bone to point in a direction that is a multiple of 45 degrees.

Note that bones don't have to be touching to have a parent-child relationship. In the first example in this chapter, the upper arm bones are children of the spine, even though they are separated from it by a small distance. This will often be the case - arms should rotate about the shoulders, not the neck, even though they move when the spine moves.

Translate Bone
This tool (along with the Rotate Bone tool) is used to reposition bones after they've been created. If you've added a new bone in the wrong place, or you just want to move it later on, click and drag it with this tool. Clicking near the base of the bone will move its position, while clicking near the tip will move the tip around, changing the bone's length and direction. Note that if the bone has any child bones, they will be moved as well.

Holding the <shift> key will cause the bone to only move horizontally or vertically relative to its parent (if you click near the base), or to point in a direction that is a multiple of 45 degrees (if you click near the tip).

If any objects in other layers have been bound to the bone, they will not move. This tool is for positioning bones, not manipulating the entire object - that kind of thing happens in Animation mode.

Rotate Bone
The Rotate Bone tool is used to change the direction a bone is pointing in. Click the tip of a bone, and drag it in circles around its base to change its direction. Hold the <shift> key to constrain the bone's direction to a multiple of 45 degrees.

Re-Parent
Sometimes when building a skeleton, you may accidentally add bones to the wrong parent. Later, when you discover the error, deleting bones and adding new ones is just too much work. Instead, use the Re-Parent tool to change a bone's parent. First, select the bone whose parent you want to change (using the Select Bone tool). Then, using this tool, click on the new parent bone. (The new parent will become highlighted in blue.) If you want to turn the selected bone into a root bone (one that has no parent), just click on the background.

Attach Layer to Bone
A bone layer can be contained within another bone layer. For example, you could create a "hand" layer and place that within an "arm" layer. To attach the hand to the arm, use this tool. Just click on the bone in the parent layer that you want to connect to, and the entire layer will move with that bone. In our arm/hand example, you would click on the bone nearest the wrist to attach the hand to the end of the arm.

Test Bones
The Test Bones tool is a glimpse of what you'll see in Animation mode. It is used to test whether a skeleton is set up and working properly. Although it moves bones and points around, the changes it makes are only temporary. When you switch back to another tool, the skeleton is reverted back to its original shape.

To test a skeleton, just click and drag the various bones that make it up. If points have been bound to the bones, they will move as well. The way the skeleton and the bound points move with this tool is exactly how they will move in Animation mode. If some part of the skeleton doesn't move correctly, you can find out with this tool and fix it before you start animating.

Move Layer
Use this tool to move the entire layer. It doesn't matter what points are selected - everything in the layer will move when you use this tool. Holding the <shift> key while using the Move Layer tool will constrain the layer to only move vertically or horizontally.

Scale Layer
Use this tool to resize the entire layer. Holding the <shift> key while using the Scale Layer tool will tell Moho to resize the layer by the same amount horizontally and vertically (if you drag in a diagonal direction), or to resize the selection in only the horizontal or vertical direction (if you drag the mouse horizontally or vertically).

Rotate Layer
Use this tool to rotate the entire layer. Holding the <shift> key while using the Rotate Layer tool will constrain the rotation to 45 degree increments.

Set Layer Origin
Click anywhere in the layer to set the origin to that point. The origin of a layer is indicated by the crosshair displayed when editing that layer. The origin is the point that the layer rotates around when using the Rotate Layer tool, and is also the point that the layer resizes around when using the Scale Layer tool.