Paint texture maps in 2D

Painting models using the 3D paint tools is extremely useful, however, there may be times when being able to paint on the model as a flattened version (as it appears in the UV View) can be very useful.

The Flatten to UV Space feature (Mesh > Flatten to UV Space) (Hotkey: Alt + T) lets you paint on a flattened representation of the mesh.

Flatten to UV Space creates a copy of the selected model with vertex positions that are identical to the UV texture coordinates of the original 3D model so you can paint or edit your textures on a flattened version. The original model is made temporarily invisible to let you paint on the 2D copy.

Since the model is flattened and laid out as it appears in the UV View it becomes much easier to correlate how the painted textures appear in relation to the UV shells without having to switch to the UV View.

Since all components of the model are visible in a flattened layout, you can:

Use large paint brushes to quickly apply or edit paint on large regions of the model without worrying that you’ll bleed onto another region, and without having to tumble around the object in the 3D View.
Paint textures in the flattened view that would otherwise be difficult to paint in 3D. For example, painting a texture for a tread pattern on a tire, or a logo type is easier to create in a flattened view.
Use the Clone Tool to copy textured areas from one region to another that would otherwise not be possible in the 3D View because of the location on the model or the camera angle.
Touch-up regions that were occluded from receiving paint due to the model’s surface texture (that is, folds and wrinkles) after using the Projection tool.

In addition, The Flatten to UV Space feature can be used for minor repositioning of UV texture coordinates on the flattened 2D version. For more information, see To adjust UV positions on a flattened model

NoteUV edits are only applied to the original 3D version of the model when Alt + T is pressed again.

To paint on a flattened model

Select the model(s) that you want to paint on as a flattened object.
You can flatten one or more models at time if necessary by selecting them using the Objects selection tool.
Select Mesh > Flatten to UV Space (Hotkey: Alt + T).
A copy of the selected model is created as a flattened version with vertex positions that are identical to the UV texture coordinates on the original model. The model appears unfolded exactly like its associated UVs so may likely appear in multiple flattened pieces.

The original 3D version of the model is made temporarily invisible. (This is evident in the Object List). By default, the flattened model appears in the same camera position as the 3D version.

NoteIf you want the flattened model to automatically appear in an orthographic view (planar to the view), turn on the Autofocus on Flatten preference located in the Focus section of the Preferences window. Otherwise, the model will appear flattened relative to the current camera position.

If multiple meshes are flattened at once, they may appear on top of each another in the 3D View. You can select each mesh in turn and translate them apart from each other in order to paint on them.
Create a paint layer, select a paint tool, and begin painting on the flattened model.
NoteBoth versions of the model (3D and 2D) reference the same texture map and can be displayed/have paint applied in the 3D View. The next step describes how to display both items simultaneously.
While the 2D version of the model is visible in the 3D View, turn on the original 3D version by locating it in the Object List and turning on its visibility icons within its hierarchy.
Now you can paint on either version of the model and the associated texture maps will update automatically.
To display the original 3D version of the model, select Mesh > Unflatten from UV Space or press Alt + T.

To adjust UV positions on a flattened model

The Flatten to UV Space feature can be used to perform simple repositioning of UV texture coordinates on a flattened 2D version of a model.

For example, the Pinch, Grab, or Smear tools can perform basic UV position adjustments on the model since they work within the plane of the flattened surface vs. along the normal. Other sculpt tools displace the vertices normal to the mesh so are not suitable for UV edits. For more extensive UV modifications it is recommended that another application with UV editing capabilities be used.

NoteAny UV modifications that are applied to the flattened mesh are applied to the original 3D model only when it is made visible as a 3D model once again by pressing Alt + T.

Select the model(s) whose UV positions you want to adjust.
You can flatten one or more models at time if necessary by selecting them using the Objects selection tool.
Select Mesh > Flatten to UV Space (Hotkey: Alt + T).
A copy of the selected model is created as a flattened version with vertex positions that are identical to the UV texture coordinates on the original model. The model appears unfolded exactly like its associated UVs so may likely appear in multiple flattened pieces.

The original 3D version of the model is made temporarily invisible. (This is evident in the Object List). By default, the flattened model appears in the same camera position as the 3D version.

NoteIf you want the flattened model to automatically appear in an orthographic view (planar to the view), turn on the Autofocus on Flatten preference located in the Focus section of the Preferences window. Otherwise, the model will appear flattened relative to the current camera position.

If multiple meshes are flattened at once, they may appear on top of each another in the 3D View. You can select each mesh in turn and translate them apart from each other in order to paint on them.
From the Sculpt Tools tray, select either the Pinch, Grab, or Smear tool.
NoteThe Pinch, Grab, and Smear sculpt tools have specific behaviors for modifying the vertices that may be useful depending on the type of UV edits you require. For more information on these tools, see Sculpt Tools tray.

NoteAny modifications you make to the UVs will not be applied to the original model until display the 3D version again.
To display the original 3D version of the model, select Mesh > Unflatten from UV Space or press Alt + T. Note how the UV edits have modified the appearance of the applied texture map.