2D Animation

Workflow

1. Select the Sprite in the Sprite Editor.

2. Build the Sprite Bones hierarchy in the Bone Editor (menu: Sprite Editor > Bone Editor).

3. Generate and edit geometry, and assign skin weights in the Geometry And Weight Editor (menu**: Sprite Editor > Geometry And Weight Editor).

4. Place the Sprite in a Scene and add the Sprite Skin component to generate the bones of the Sprite.

5. The Sprite is ready to be animated!

Bone Editor

Create and define the bones for your Sprites and their hierarchy in the Bone Editor.

Create and Edit Bones

When building bones to for the animation of a Sprite, the first bone created is the Root bone for the bone hierarchy of that Sprite. There are two modes for creating bones - the Create Chain Bone mode, and the Create Free Bone mode. In Create Chain Bone mode, newly created bones are automatically parented to the previous bone in the hierarchy. In Free Bone mode, new bones are parented to the currently selected bone regardless of their position in the hierarchy. If no bone is currently selected, the new bone is automatically parented to the Root bone by default. If no tools are selected, the editor is in Transform mode, and a bone's Pivot, Body and Tail can be selected and transformed.

Create Chain Bone tool

Select the Create Chain Bone tool and click anywhere in the Sprite to start creating a chain of bones. Press Esc to deselect the tool. In this mode, it is easy to control entire chains of bones and their lengths and positions, as each bone is connected to each other together in a continuous chain.

Create Free Bone tool

The Create Free Bone tool is used to create bones that do not form a continuous chain of bones.

1. Select a bone that will be the parent of the new bone. If no bone is selected, the *Root * bone is the default parent.
2. Select the tool, then click anywhere to set the start/Pivot of the new bone.
3. Move the cursor to where the bone should end, and click to set the Tip of the bone. The new bone is created.

Free Move Tool

The Free Move tool is used to detach a bone from a chain and move it independently. It will no longer be connected to the chain but will still be parented to it original parent bone.

Parent Tool

The Parent Tool is used to change the parent of a child bone. First select the child bone, then click Parent Tool then click on the new target parent.

Split Tool

The Split Tool splits a selected bone. First select a bone, then select the Split Tool to split the selected bone into two.

Delete Tool

Select a bone, then click the Delete Tool to remove it.

Bone Editor Shortcut Keys

Tool	Shortcut
Create Chain Bone	B
Create Free Bone	N
Free Move	M
Parent Bone	P
Split Bone	S
Delete	Del
To deselect all tools	Esc

Geometry and Weight Editor

This editor is where Sprite geometry is generated, and vertex weights are then assigned to the bones to deform the geometry.

Generating Geometry Automatically

Sprite geometry can be generated automatically or created manually.

To auto-generate the mesh, set the editor to Geometry mode.

Then select the Generate button at the top-left of the menu bar.

Adjust the following parameters to refine the generated geometric mesh.

Property	Function
Outline Detail	Density and accuracy of the mesh to the Sprite outline.
Alpha Tolerance	Threshold for transparency considered when generating the outline.
Subdivide	Subdivides the mesh to increase tessellation. Higher values increase the tessellation and complexity of the generated mesh.

Creating Geometry Manually

Create mesh geometry created manually in the Create Vertex or Create Edge modes., then double-click within a Sprite's outline to select it.

From the top menu, select Create Vertex and click anywhere within the Sprite to create vertices. Then select Create Edge and click on vertices to connect them together to form new edges. Select Split Edge and then click on an edge to split it into multiple pieces.

You can create vertices and new edges directly in Selection mode as well. While in Selection mode, double-click anywhere on the Sprite to create vertices. Hold Shift to connect a selected vertex to another to create an edge.

Weights Mode

Select the Weight mode, and then select a Sprite to begin applying skin weights. Click Auto to automatically generate weights based on the Sprite's bones, which can be edited manually later.

Editing Skin Weights

The Weight Editor is used to manually edit skin weights.

There are two tools to edit the Weights - the Slider and the Brush. The Slider allows direct manipulation of the values of selected vertices; while the Brush tool allows you to 'paint' skin weights directly on the mesh.

Weight Editor Settings

Property	Function
Mode	Current behavior mode of the Weight Editor
Add and Subtract	Increases/Decreases influence on vertices around the selected bone
Grow and Shrink	Increases/Decreases influence on vertices that are already affected by the selected bone.
Smooth	Averages the weights of vertices with their neighbors, creating smoother deformations.
Bone (unavailable if Mode: Smooth)	Displays currently selected Bone. A different Bone can be selected via the drop-down menu.
Normalize	Enable to ensure the normalized weight of selected vertices is equal to 1.
Amount	Amount of weight applied on selected vertices
*Following available in the Brush Weight editor only
Size	Size of the brush cursor.
Hardness	Amount of weight applied by the brush. Higher values increase the weight per brushstroke.
Step	Number of increments needed to apply the full weight of brush.

The weights for selected vertices can be viewed and further adjusted with the vertex inspector located at the bottom-left of the Editor window.

You can preview the effect of the painted weights within the Sprite Editor. Select and hold a bone to move or rotate it. The Sprite's geometry mesh deforms according to the weights painted. Releasing the bones resets them and the mesh back to their original state.

Sprite Skin Component

The Sprite Skin component is needed for the bones to deform the Sprite mesh in the Scene.

1. Drag and drop the Sprite Asset onto the Scene after its bones, geometry, and weights have been are set-up in the Sprite Editor.
2. Add the Sprite Skin component to the Sprite.
3. Click Create Bones to generate the bone hierarchy of the Sprite in the Scene.

Select and hold a bone to pivot it around its head and deform the Sprite's mesh directly in the Scene to begin animating it.

Shift+click to select multiple bones at once. Moving selected bones together deforms the mesh across all of them.

Bones that are not directly chained together can also be selected and moved together. Areas of the mesh influenced by the unselected bones are not deformed.

Select and hold the head of a bone to detach it from the previous bone in the chain, the mesh will deform accordingly.

Use the standard Transform tools to deform the Sprite's geometry mesh with greater precision. However, note that the Rect Transform tool cannot be used to transform the bones.