In Blender, you don't assign an entire object to a vertex group; rather, you assign specific vertices (or portions of the mesh) of an object to a vertex group. Vertex groups are a fundamental part of a mesh object's data, used for various purposes like rigging, modifiers, particle systems, and more.
Understanding Vertex Groups
Vertex groups are essentially named lists that store vertex indices and optionally, a weight value (typically between 0 and 1) for each vertex in the group. These weights determine how strongly a vertex belongs to or is influenced by that group.
Assigning Vertices Manually
The primary way to manually assign vertices to a vertex group is through the Mesh Data Properties tab.
Steps for Manual Assignment:
- Select Your Object: Ensure the mesh object you want to modify is selected.
- Go to Edit Mode: Switch from Object Mode to Edit Mode (Tab key). This is crucial as vertex groups are a property of the mesh geometry.
- Access Mesh Data Properties: In the Properties Editor, find the Mesh Data Properties tab (it looks like a green triangle, often just below the wrench icon for Modifier Properties).
- Locate Vertex Groups Panel: Within the Mesh Data tab, find the panel labeled "Vertex Groups".
- Create or Select a Group:
- Click the + button to add a new vertex group. It will appear in the list, usually named "Group".
- Double-click the group name to rename it (e.g., "Arm_Right", "Deform_Part").
- Alternatively, select an existing group from the list you want to add vertices to.
- Select Vertices: While in Edit Mode, select the vertices you wish to assign to the currently active group. You can select individual vertices, edges, faces, or use selection tools like box select, circle select, or linked selection (L key).
- Assign Vertices: In the Vertex Groups panel, ensure the correct group is active (highlighted). Set a Weight value (1.0 is default for full influence). Click the Assign button.
Selected vertices are now assigned to the active group with the specified weight.
Managing Assignments:
The Vertex Groups panel offers additional tools:
- Remove: Removes selected vertices from the active group.
- Select: Selects all vertices currently assigned to the active group.
- Deselect: Deselects all vertices currently assigned to the active group.
- Weight Slider: Adjusts the weight assigned when using the "Assign" button.
Here's a quick look at the core operations:
| Operation | Description | Location |
|---|---|---|
| Add Group | Create a new vertex group | Mesh Data Properties Tab |
| Assign | Add selected vertices to the active group with weight | Mesh Data Properties Tab |
| Remove | Remove selected vertices from the active group | Mesh Data Properties Tab |
| Select | Select vertices in the active group | Mesh Data Properties Tab |
| Deselect | Deselect vertices in the active group | Mesh Data Properties Tab |
Assigning Vertices Automatically (e.g., Rigging)
Vertex groups are frequently generated and assigned automatically, most notably during rigging (connecting a mesh to an armature).
As referenced, if you go into the mesh data tab after parenting a mesh to an armature with automatic weights, you can see newly generated vertex groups each named after the bone they are assigned to. Blender calculates how much each bone influences different parts of the mesh and automatically assigns vertices to the corresponding bone's vertex group with appropriate weights. This process is called "Weight Painting" or "Automatic Weights".
Other modifiers or operations can also automatically create and assign vertices to groups based on criteria like proximity to another object (e.g., Weight Proximity Modifier) or other mesh properties.
In summary, while you interact with vertex groups via the Mesh Data Properties tab, vertex assignments can be done manually in Edit Mode or generated automatically by features like rigging or modifiers.
