UV Unwrapping - Blender Master Class: A Hands-on Guide to Modeling, Sculpting, Materials, and Rendering - page 117

them so that they filled the width of the UV grid
(see Figure 8-10). Later, this would allow me to tile a
texture multiple times around and along the length
of the trunk and roots without creating too many
seams where the textures didn't match.

Multiple UV Maps
You can add multiple UV-coordinate sets to an
object and edit them independently. This is good
for making use of multiple textures in complex
materials and when texture painting. When texture
painting, you can use one UV set to neatly pack your
UV islands for your final texture and use another to
assign seamless textures or photos to clone texture
information from. In subsequent chapters, I will
sometimes refer to creating extra UV sets for pur-
poses like these.
For the trees, I created a second UV coordinate
set to match up with a tileable bark texture, saving
the first UV set to use for baking ambient occlusion
and the final texture maps. To create this second
set, I opened the Object Data tab of the Properties
editor and clicked the + icon in the UV Maps panel
to create a new UV set. You can choose between
your existing UV sets from this panel and edit
whichever is active. To unwrap the second UV set
for my tree, I used the Follow Active Quads opera-
tor for the parts of the trees with approximately
cylindrical topology and unwrapped and packed

Sharing UV Space Between Objects
Just as you'll usually want to combine all of a single
object's UV islands in the UV grid, when it comes to
unwrapping multiple objects for texturing, you may
want them all to share the same UV space so that
they can all use the same texture. Doing so will save
you time when painting textures and memory when
rendering. To see the UV coordinates of multiple
objects in the UV Image editor at the same time,
select the objects and then enter Edit mode for the
one you want to edit. In the UV Image editor, turn
on View 4 Draw Other Objects . The UV coordinates
for the selected objects will now be visible in gray
(though only the current object will be editable),
allowing you to align multiple objects on the same
UV grid (see Figure 8-11).

Figure 8-10: In the second UV set for the trees, I unwrapped the UV islands using Follow Active Quads and then scaled to fill the
width of the UV grid. Later, this will be used for aligning tileable textures along the length of the trees and their roots.