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Weight Paint Mode

The Weight Paint mode is used to create and modify vertex groups. A vertex may not only be a member of one or more vertex groups, but also may have a certain weight in each group. The weight symbolizes its influence on the result.

Weight painting is primarily used for rigging meshes, but may also be used for controlling particle emission, and hair density.

When you change to Weight Paint mode you see the selected object (if you have not created any groups yet), in a slightly shaded, blue color (Image 2).

The color visualizes the weight of each vertex of the currently active group. A vertex drawn in blue indicates either: a weight of zero, not in the active group, or not in any group at all.

You can customize the colors in the weight gradient by enabling Custom Weight Paint Range in the System tab of the User Preferences.

You assign the weight of each vertex by painting on the mesh with a certain color. Starting to paint on a mesh will automatically creates a new vertex weight group (when no group existed or is active). If a vertex doesn’t belong to the active group it is automatically added (if the option Vgroup is not set), even if you paint with a weight of “0”. The used color spectrum is shown in (Image 3).

Image 3: The color spectrum and their respective weights.

You paint on the mesh with a brush. The color only influences the vertices, not the faces nor the edges, so don’t try and paint those. There is a tool panel for the brush in the Editing context (F9) as well as in the 3D Window (press N to open it).

	Weight Painting survival tips
	A few tips that will save you some hassle when painting weight: Press F in Weight Paint mode to resize the brush Draw a Clipping Border with AltB. It will separate a visible part of the 3D window. You can draw only in this part. If you press AltB again the clipping border will be removed.

Paint Panel

The tools in the Paint panel are sophisticated, and you can apply weight in the finest nuances. But normally you won’t need all these options, and you will apply weight using a few techniques. The most used and important settings are drawn in bold.

Weight

The weight (color) that is used to paint. The button row below contains several weight presets to paint. By default, painting works with an absolute fixed amount (like Gimp or Photoshop defaults), so you can set for example “0.2 weight” to vertices while keeping the mouse button pressed, whatever their original weight was.

Auto Normalize

Ensures that all vertex groups add up to 1 while painting.

Radius F

The size of the brush, which is drawn as a circle during painting.

Strength

How powerful the effect of the brush is, when applied.

Jitter

Jitter the position of the brush while painting

Weight Tools

When these tools are activated, additional options are available in the tool settings section at the bottom of the properties panel.

Normalize All

Normalization makes sure that the sum of the weights for each vertex in all of the groups is equal to 1. This tool normalizes all of the vertex groups.

Lock Active

This keeps the values of the active group while normalizing others.

Normalize

This normalizes the just the values of the current vertex group

Invert

Inverts the weight values (1-value)

Add Weights

Add vertices from groups that have zero weights before inverting

Remove Weights

Remove vertices from groups that have zero weights before inverting

Clean

Remove vertex group assignments which are not required

Limit

Remove weights under this limit

All Groups

Clean all vertex groups

Keep Single

Keep vertices to at least one group when cleaning

Levels

Adjust weight values using the following tools:

Offset

Value to add to weights

Gain

Value to multiply weights by

Gradient

See Gradient section below...

Stroke

Airbrush

The Airbrush option applies the paint effect while holding the mouse.

Smooth Stroke

Causes brush to lag behind mouse and follow a smoother path.

Radius

Minimum distance from last point before stroke continues

Factor

Higher values give a smoother stroke

Space

Limit brush application to distance specified by Spacing value, as a percentage of brush radius.

Curve

Set a custom brush shape by reshaping the curve

The bottom row of button are preset curve shapes.

Options

All faces

If this is turned off, you will only paint vertices which belong to a face on which the cursor is. This is useful if you have a complicated mesh and you would paint on visually near faces that are actually quite distant in the mesh.

Normals

The vertex normal (helps) determine the extent of painting. This causes an effect as if painting with light.

Spray

The Spray option accumulates weights on every mouse move.

X-mirror

Use the X-mirror option for mirrored painting on groups that have symmetrical names, like with extension .R/.L, or _R/_L. If a group has no mirrored counterpart, it will paint symmetrical on the active group itself. You can read more about the naming convention in Editing Armatures: Naming conventions. The convention for armatures/bones apply here as well.

Topology Mirror

Use topology based mirroring, for when both side of a mesh have matching mirrored topology.

Unified Settings: The Size and Strength of the brush can be set to be shared across different brushes, as opposed to per-brush.

Appearance

Here you can set the color of the brush cursor, or load a custom icon from a file.

Tool

The tool defines how the weight values are applied to the vertices.

Mix

The new color replaces the old color. Applying more and more of the new color will eventually turn it the new color.

Add

The new color is added to the old. Note that you must think in weight here (not in RGB colors): adding blue (0.0) to something won’t modify it, adding green (0.5) to green will give red (1.0), …

Sub

The new color is subtracted from existing. Here again you have to think in terms of “weight”, and not “RGB colors”.

Mul

The new color is multiplied by the old.

Blur

Blurs the color with surrounding values.

Lighten

Only paints vertices “darker” (lower weight) than the current “color”, “lightening” them.

Darken

Only paints vertices “lighter” (higher weight) than the current “color”, “darkening” them.

• Vgroup: Only vertices which belong to the active vertex group are painted. Very useful for clearing up and refining vertex groups without messing other groups up.

Weight Gradient

This is an interactive tool that for applying a linear/radial weight gradient, this is useful at times when painting gradual changes in weight becomes difficult. The gradient tool can be accessed from the Toolbar as a key shortcut (AltLMB drag) - Linear, (Alt⇧ ShiftLMB drag) - Radial.

The following weight paint options are used to control the gradient

• Weight - The gradient starts at the current selected weight value blending out to nothing.
• Strength - Lower values can be used so the gradient mixes in with the existing weights (just like with the brush)
• Curve - The brush falloff curve applies to the gradient too, so you can use this to adjust the blending.

Since the gradient applies to the entire mesh you will typically want to use it with selected vertices.

Vertex Selection Masking

Vertex selection is useful to limit the vertices used with tools or when painting.

This can be accessed from the header or toggled with the V key.

Standard selection operations work including (de)select all, invert, border, circle and lasso.

Note that the "Limit selection to visible" option is also supported.

Face Selection Masking

If you have a complex mesh it is nearly impossible to reach all vertices in Weight Paint mode. And it is quite difficult to tell where the vertices are exactly. But there’s a very good and easy solution: the Face Selection Masking mode. The Face Selection masking button on the header panel allows you to select faces and limit the weight paint tool to those faces.

Select mode has many advantages over the normal Weight Paint mode:

1. The original mesh is drawn, even when subsurface is active. You can see the vertices you have to paint over.
2. You can select faces, only the vertices of selected faces are painted on.
3. Selecting tools include:
   • RMB – Single faces. Use ⇧ ShiftRMB to select multiple.
   • A – All faces, also to de-select.
   • B – Block/Box selection.
   • BB – Select with brush.
   • CtrlL – Select linked.
   • In the Select menu: Faces with Same UV, also invert selection (Inverse).
4. You may hide selected faces with H and show them again with AltH (Image 6).

Image 6a: Select interfering faces…

Image 6b: … and hide them with H.

• To constraint the paint area further you may use the Clipping Border. Press AltB and LMB -drag a rectangular area. The rest of the 3D window is hidden. To show everything again, just hit another time AltB.

Weight Painting for Bones

This is probably the most often used application of weight painting. When a bone moves, vertices around the joint should move as well, but just a little, to mimic the stretching of the skin around the joint. Use a “light” weight (10-40%) paint on the vertices around the joint so that they move a little when the bone rotates. While there are ways to automatically assign weights to an armature (see the Armature section), you can do this manually. To do this from scratch, refer to the process below. To modify automatically assigned weights, jump into the middle of the process where noted:

• Create an armature.
• Create a mesh that will be deformed when the armature’s bone(s) move.
• With the mesh selected, create an Armature modifier for your mesh (located in the Editing context, Modifiers panel). Enter the name of the armature.

Pick up here for modifying automatically assigned weights.

• Select the armature in 3D View, and bring the armature to Pose mode (Ctrl⇆ Tab, or the 3D View window header mode selector).
• Select a desired bone in the armature.
• Select your mesh (using RMB ) and change immediately to Weight Paint mode. The mesh will be colored according to the weight (degree) that the selected bone movement affects the mesh. Initially, it will be all blue (no effect).
• Weight paint to your heart’s content. The mesh around the bone itself should be red (generally) and fade out through the rainbow to blue for vertices farther away from the bone.

You may select a different bone with RMB . If the mesh skins the bones, you will not be able to see the bones because the mesh is painted. If so, turn on X-Ray view (Buttons window, Editing context, Armature panel). While there on that panel, you can also change how the bones are displayed (Octahedron, Stick, B-Bone, or Envelope) and enable Draw Names to ensure the name of the selected bone matches up to the vertex group.

If you paint on the mesh, a vertex group is created for the bone. If you paint on vertices outside the group, the painted vertices are automatically added to the vertex group.

If you have a symmetrical mesh and a symmetrical armature you can use the option X-Mirror. Then the mirrored groups with the mirrored weights are automatically created.

Weight Painting for Particles

Faces or vertices with zero weight generate no particles. A weight of 0.1 will result in 10% of the amounts of particles. This option “conserves” the total indicated number of particles, adjusting the distributions so that the proper weights are achieved while using the actual number of particles called for. Use this to make portions of your mesh hairier than others by weight painting a vertex group, and then calling out the name of the vertex group in the VGroup: field (Particles panel, Object context).