Weight Painting
Weight painting is probably the fastest way to assign bone weights to your model. To enter Weight Paint Mode, just go to the Interaction Mode selector in the 3D View header and select Weight Paint. Now you’ll see the model with blue, yellow, green, and red applied; the colors represent the weights of the currently selected bone. You can also switch to this mode by pressing Ctrl + Tab.
Tip
Before you start setting up the bone weights for the model, you may want to change the armature’s display to Stick (in the Display panel, on the Armature tab) so the bones don’t block your view of the mesh; also, only turn on the deformer bones layer.
Weight Paint Mode is very similar to Texture Paint Mode: on the left, you’ll see painting tools and options in the Tools Region (see Figure 11.11).
When you add an Armature modifier to a mesh using the Automatic Weights option, vertex groups are created in the mesh, one for each bone, and they have the same names as the bones. Each one of those vertex groups stores the weights that define the influence of each bone in the armature.
Here are some instructions on how to work in Weight Paint Mode:
On the left side, in the Tools Region, you’ll find a series of settings to control brush options while you work in Weight Paint Mode. At the top, you’ll find the different brush types such as Add, Subtract, Draw, and Blur. Each type has different effects on the weights when you paint by left clicking and dragging over the vertices.
You can also set the size, strength, and weight of the brush. Just as you did in Texture Paint Mode, you can change the size and strength of the brush by pressing F and Shift + F in the 3D View.
RMB allows you to select other meshes and paint their weights. However, they’ll only be in Weight Paint Mode if you left them in that mode; otherwise, when you select them with RMB click, you will enter Object Mode. Press Ctrl + Tab with a mesh selected to switch between Object Mode and Weight Paint Mode.
To select the bone weight that you want to paint, go to the Mesh tab in the Properties Editor and, in the Vertex Groups panel, select the desired Vertex Group from the list (another place where it’s useful to have the bones named correctly).
Tip
Selecting the vertex groups from the list is not the fastest way, though. Instead, you can select the armature and make sure you’re in Pose Mode. Now select the mesh and, if you have the deform bones visible in the armature, you’ll be able to select the bones with RMB while you paint weights! When you select a bone, you’ll automatically see its influence on the vertices and the bone’s vertex group will be selected. Much faster than going through the list, right?
While painting, press G, R, or S to move, rotate, or scale the bone. This will allow you to move the character while you paint and test if the weights behave properly. (From time to time, you might want to reset some bones to their original positions: just press A to select all of them or select the ones you want to reset, and press Alt + G, Alt + R, and Alt + S to reset their location, rotation, and scale).
You can even take this further and create animations that move the bones you’re weighting so you can see how they behave by dragging the cursor in the timeline across the animation. You’ll learn how to do this in the next chapter.
On the Options tab in the Tools Region are some features you may find useful. One of them is the X-Mirror option: if your mesh is exactly the same on both sides of the X-axis, then X-Mirror will mirror the weights you paint on one side to the corresponding bones on the other side. Of course, that will only work properly if your bones are also correctly named with their left and right suffixes.
The Blur brush is very handy. Paint in basic weights first and, where you need the weight borders to be soft, just pick the Blur brush to paint in those borders. Keep in mind that this brush blurs the weights of the vertices inside the brush radius, so you may need to make the brush bigger in order to use it for this purpose.
Tip
It’s usually easier to see what you’re doing with weights when you’re in the Wireframe display mode (Z). You’ll see everything in wireframes, except for the object you had selected when you jumped into Weight Paint Mode; you’ll see that object in shadeless colors representing the weights.