Normal Brush Tool

The Normal Brush submenu contains controls for the brush.  To begin, select the object you want to adjust normals on and then click the Start Normal Tool button to activate the brush.  The normals of the object will then be shown overlaid on the mesh and you can click and drag with the brush to adjust them.

Strength
Adjust the strength of the brush stroke.

Pen Pressure
If checked, the strength of the brush stroke is multiplied by the pressure of your pen.

Normal Length
Change the display size normals are drawn in the overlay.

Radius
Radius of the normal brush.  You can also press the *[* and *]* keys to change the size.

Front Faces Only
If checked, your brush stroke will only affect faces facing the viewer.  Otherwise, all vertices within a sphere the size of the brush are affected.

Selected Faces Only
If checked, your brush stroke will only affect faces that have been selected in edit mode.  (The Normal Brush tool still operates in Object mode).

Symmetry
For each axis checked, any tweak made on one part of the model will also be mirrored across the axis.

Mode Buttons

• Comb - Normals will point in the direction that you stroke the brush.
• Fixed - Brush stroke will paint all normals to point in a single direction.
• Attract - Normals will point toward origin of selected target object.
• Repel - Normals will point away from origin of selected target object.
• Smooth - Average the values of the normals under the brush.
• Vertex - Paint normals to reflect the underlying geometry.  This effectively 'erases' your tweaks.

Normal
In Fixed mode, indicates the direction of the normal you are painting.  You can set it directly by typing in the normal or select Exact Normal to get a trackball you can use to adjust the normal.  You can also click the Pick Normal button to get an eyedropper to pick the normal from another piece of geometry in the scene.

Target
In Attract and Repel modes, indicates the target objects that normals will point toward/away from.

Undo/Redo
While the tool is running, you can use CTRL-Z to undo your most recent brush stroke and CTRL-SHIFT-Z to redo it.  The history is limited to 10 strokes.  Once you press Enter to finish editing normals, all your changes are added to Blender's undo queue as a group and you can no longer undo individual strokes.

Cancelling
Pressing Esc or Right Mouse Click will cancel your editing, discarding all changes.


Fix Seam Normals Tool

Also included under the Fix Seam Normals menu is a control to automatically copy normals across seams.  Simply select two or more objects with edges that meet.  Then press the Copy Seam Normals button.  The normals from the active object will be copied to the other selected objects wherever the selected object' vertex is snapped to the same spot as the active object's vertex.

Installation

To install, download this archive as a .zip file.  Then start blender and open your Edit > Preferences.  Select the Add-ons tab and then press the Install button.  Browse to the .zip file and select it.  Finally, tick the checkbox next to Add Mesh: Normal Brush.