Can't select vertex group of armature in Blender? Weight painting, step by step

Weight painting decides how much each bone moves each vertex of a mesh. This guide binds a mesh to an armature, selects a bone to display its vertex group, covers the brushes and cleanup tools, and lists why Blender sometimes refuses to select a bone or its group. Menu names are those of Blender 5.2.

Vertex groups, bones and weights

A vertex group is a named list of vertices, each with a weight between 0 and 1. The Armature modifier links every bone to the vertex group with exactly the same name: a bone called forearm.L only deforms the vertices of the forearm.L group. The weights on one vertex are read relative to each other, so a vertex at 0.5 for upper_arm.L and 0.5 for forearm.L follows both bones equally.

Vertex groups are listed in the Object Data tab of the Properties editor, Vertex Groups panel. Renaming a bone in Blender also renames the matching group on meshes that use the armature through an Armature modifier. Renaming a group by hand does not rename the bone, and the link is lost.

Bind the mesh to the armature

1. In Object Mode, select the mesh, then Shift+click the armature so it is selected last.
2. Press Ctrl+P and pick one of the options under Armature Deform.

Each option makes the armature the parent and adds an Armature modifier to the mesh, with the armature in its Object field. They differ in what goes into the vertex groups.

• With Automatic Weights creates a group for each deforming bone and fills it from the distance between vertices and bone (the bone heat method). The usual starting point for a character.
• With Empty Groups creates the same groups with no weights, for when you paint everything yourself.
• With Envelope Weights fills the groups from each bone's envelope, set by its Distance and Radius values in the Bone tab. It suits simple, mechanical shapes.
• Armature Deform on its own sets the parent and the modifier but creates no vertex group.

The manual warns that Automatic and Envelope weights override groups that already share a bone's name. Both offer X Mirror in the Adjust Last Operation panel, to compute the weights symmetrically along X. If Blender reports "Bone Heat Weighting: failed to find solution for one or more bones", some groups stayed empty and need painting by hand.

How to select a bone in Weight Paint

1. In Object Mode, click the armature, then Shift+click the mesh, which becomes the active object.
2. In the mode selector of the 3D Viewport header, choose Weight Paint. Blender puts the armature in Pose Mode at the same time, because it is selected and drives the mesh through its modifier.
3. Alt+click a bone. Its vertex group becomes active and the mesh shows its weights. Ctrl+Shift+click does the same, which you need if Emulate 3 Button Mouse is on in Preferences, Input, since that option takes over Alt+click.
4. Paint with the left mouse button.

Many tutorials say Ctrl+click. That was the shortcut up to Blender 3.6. Since 4.0, Ctrl+drag paints an inverted stroke: with the default Mix blend it paints 1 minus the Weight value, so at a Weight of 1.0 it removes influence instead of selecting anything.

Blue means 0, red means 1, and green, yellow and orange sit in between. In the Weight Paint overlays popover, next to Viewport Overlays in the header, set Zero Weights to Active to show in black the vertices with no weight in the active group. Shift+Ctrl+X (Sample Group) lists the groups under the cursor.

Can't select the vertex group or the bone? Seven causes

1. The mesh has no Armature modifier. The armature then never enters Pose Mode with the mesh, and the Bone Selection button of the header is unavailable. In the Modifiers tab, check for an Armature modifier with your armature in its Object field, or parent again with Ctrl+P.
2. The armature was not selected. Blender only switches an armature to Pose Mode for Weight Paint if it is selected and visible at that moment. Go back to Object Mode, click the armature, Shift+click the mesh and switch again. The manual's route also works: armature in Pose Mode with Ctrl+Tab, Edit > Lock Object Modes unchecked in the top bar, then the mesh switched to Weight Paint.
3. You clicked with Ctrl. With the default left-click select, use Alt+click or Ctrl+Shift+click, and Ctrl+Z if the Ctrl+click painted something.
4. Selection masking is on. The three header buttons are Face Selection, Vertex Selection and Bone Selection (1, 2, 3). With either of the first two active, Alt+click selects faces or vertices. Press 3.
5. The bone is buried inside the mesh. A bone hidden by the body cannot be clicked. Before entering Weight Paint, select the armature and enable In Front in its Object Data tab, Viewport Display panel: bones are then drawn over the mesh and stay selectable.
6. The bone does not deform. When the checkbox in the header of the Deform panel (Bone tab) is off, the bone gets no group from With Empty Groups or With Automatic Weights, and its weights are ignored. Leave it off for a bone that only controls other bones.
7. The group is missing, empty or misnamed. Plain Armature Deform creates no groups, With Empty Groups leaves them empty, and a group renamed by hand no longer matches its bone. Select the bone and start painting: Blender creates its group if needed. In Edit Mode, the Select button of the Vertex Groups panel shows which vertices a group holds.

Weight Paint brushes: Draw, Blur, Average and Smear

Since Blender 4.3, brushes are assets: pick them from the asset shelf along the bottom of the 3D Viewport, or from the brush thumbnail in the tool settings. Shift+Spacebar opens the same list.

• Draw (the Paint brush) applies the Weight value according to its Blend mode. With Mix, Weight is the target reached by painting over the same spot, and Strength sets how many strokes it takes. Add and Subtract add or remove the Weight value, within 0.0 and 1.0.
• Blur smooths the weights of neighboring vertices. It ignores Weight; Strength sets how much it smooths. With any brush, holding Shift while you drag smooths for that stroke.
• Average paints the average of the weights under the brush, which evens out a patchy area.
• Smear drags the weights under the brush along the stroke, like finger painting.

Set brush size with F, Strength with Shift+F and Weight with Ctrl+F. Shift+X samples the weight under the cursor, and Ctrl+X fills the active group with the current Weight. For long transitions, Weights > Gradient (Linear) paints a falloff in one drag.

Symmetry: paint one side, get both

In the tool header, the X, Y and Z buttons next to the mirror icon repeat each stroke across the object's local axes. On a character facing the Front view, left and right lie along X, and the mesh must be symmetrical around its own origin. If the axes point the wrong way, the manual says to rotate the model in Edit Mode, not in Object Mode.

In the dropdown next to these buttons, Mirror Vertex Groups sends the mirrored stroke to the matching group: paint upper_arm.L and upper_arm.R gets the same weights. It relies on names ending in .L and .R, or _L and _R. To flip weights already painted, Weights > Mirror only works when the rest pose is perfectly symmetrical across X.

Clean up: Normalize All, Clean and Limit Total

The Armature modifier normalizes weights on its own, but normalized weights are easier to read: the color of one group then shows a bone's real share. The Weights menu has the tools.

• Normalize All makes the weights of each vertex add up to 1, except in locked groups. Lock Active, on by default, keeps the active group as it is; the manual advises turning it off the first time.
• Clean removes weights at or below its Limit, 0 by default, which deletes zero weights. Keep Single keeps every vertex in at least one group.
• Limit Total keeps a maximum number of weights per vertex, 4 by default, removing the lowest first. Use it when the program you export to accepts a fixed number of influences.

Then enable Auto Normalize in the Options panel of the tool settings to keep weights normalized as you paint. K opens the lock pie menu: a locked group cannot be painted, and Auto Normalize shares weight only between the unlocked ones.

Test the weights in Pose Mode

1. In Object Mode, select the armature and press Ctrl+Tab to enter Pose Mode.
2. Rotate bones around the joints you painted with R: bend an elbow, raise an arm, turn the head.
3. Look for pinched or stretched areas and vertices left behind, then fix them in Weight Paint. The pose stays when you switch modes.
4. Select every bone with A and clear the pose with Alt+R, Alt+G and Alt+S.

If a joint shrinks as it bends, enable Preserve Volume on the Armature modifier: it keeps the volume, with a discontinuity at 180 degrees from the rest pose. The Pose Mode guide covers posing and resetting in detail.

What next

The Blender rigging guide builds the armature and adds inverse kinematics. The T-pose guide explains why characters are usually modeled in a T-pose or an A-pose. To rig a humanoid without building the skeleton by hand, see Mixamo with Blender.