Inside of the UV preview window you can also manipulate your UV islands & more, directly. By clicking the LMB on an island, you’ll then see a manipulator gizmo. Selected islands will then highlight all edges of it’s respective polygons inside the 3D viewport.
In addition, advanced tools for editing your UV maps directly reside in the “Selected” portion of the of the retopology tools. These tools all require a selection in the UV Preview window. To select a cluster (or island) simply click on one with the LMB.

Further advanced tools for editing your UV maps directly reside in the “Selected” portion of the of the retopology tools. These tools all require a selection in the UV Preview window. To select a cluster (or island) simply click on one with the LMB.
Found in the UV Preview window, this 2D Transform gizmo lets you scale, stretch, rotate and translate whichever island you currently have selected.

You can manually place your clusters as you see fit before packing them (Optimized unwrapping) into a UV map. You must have the “Manipulator” tick box turned on to use this, it is located on the Top Bar. Use this gizmo to transform vertices, edges, faces, islands and any selection thereof (multiple islands, etc.) inside the UV Preview window.

Use this gizmo to manipulate vertices, edges, faces and whole islands inside the UV Preview window.
In the block selected you will find a set of commands that are related to the selections made in the UV Preview window. After applying the Unwrap command found in the Retopo Room, you may want to edit UV islands in the UV Preview window, before Merging your mesh into the Paint Room.

Rotate CW: This will rotate the selected island clock-wise.
Rotate CCW: This will rotate the selected island counter clockwise.
Flip U: This will flip the U of the UV map.
Flip U: This will flip the V of the UV map.
Relax: Applies a light smoothing across the selected cluster (or island) to relieve stretching or pinching.

by ALEX MEISTER

3DCoat uses a heat map color scheme to visualize your texel density.

If you are unfamiliar with the term “texel density”, it is simply the ratio of pixels used to fill a set unit size in the 3D scene.
The general goal is to have all UV islands scaled according to this ratio. In short, smaller objects in the scene should use less pixels than bigger objects.

If a UV island is scaled correctly according to its size in the scene, 3DCoat will color the island grey. Islands that are using more pixels than they should are colored red and islands using less than they should are colored blue.

Texel Density, as mentioned in the Subpart of Unwrap, ensures that each part of your model gets enough space on the uv for a texture, most of the time this is exactly what you want.

But there are certain models, especially with only 1 texture that rely on more details in a certain part. You can get this quite simple by selecting the uv you want bigger in the uv preview and scale it up. (it will become red and the rest should become blue)

Each time after making adjustments to your UV island scaling, you can press “Pack UV” to let the program arrange the best possible fit for all islands. Now you have one part that is bigger for more texture space, for an ornament or just something that needs more details than the rest since it would be closer to the camera.

As an Example of this, where I scaled down the 2 blue parts, as they hold nearly no real importance and detailing later. Scaling it down will of course show you that all the other objects are too big compared. The simplest way to do this is by scaling down the parts you don’t need that much information on and then select PackUV2.

To recap the basic workflow for taking a mesh from the Voxel Room to the Paint Room - and ultimately to the point of “Exporting” both mesh and texture data:

1. Sculpt your model in the Voxel Room and Surface Mode.
   
2. Add Custom topology by means of AUTOPO or manually within the Retopo Room.
   
3. Mark seams and Unwrap your Retopo mesh.
   
4. Manipulate UV Map elements and optimize your UV Map (in Retopo Room)
   
5. Unwrap your Retopo mesh and optimize your UV Map by “Packing” it.
   
6. Bake your Retopo mesh into the Paint Room (and “Objects” Panel) and apply your textures.
   
7. Choose “File/Export Model” - saving out all mesh and texture data according to your chosen parameters.
   

UV Preview Panel

Select UV Islands in 3D Viewport