Texture Painting - Blender Master Class: A Hands-on Guide to Modeling, Sculpting, Materials, and Rendering - page 180

To make the background of the decals transpar-
ent, I used Colors 4 Color to Alpha and selected the
background color as the color to remove. I selected
individual decals and spread them out over the body
by selecting them and then scaling, moving, and
rotating them into place. (It can be easier to do this
if you split up each decal onto its own layer by select-
ing it and pressing ctrl ‑ shift -L to float the selection
and ctrl ‑ shift -N to convert it to a layer. Then, you
can scale and rotate it independently of the other
decals. Once it's in place, you can merge the details
back onto the same layer.)
To get a better feel for the placement of your
decals, you can mark in roughly where you want
them in Blender's Texture Paint mode. Then, save
the image as a guide to use in GIMP. Once I had the
decals laid out, I set their opacity to 60 percent for
the diffuse map.
To make the decals stand out, I worked them
into the specular and roughness maps too. I dupli-
cated my decal layer from the diffuse map and
placed copies in my layer groups for the specular
and roughness maps. For the specular map, I used
Colors 4 Invert to make the decals white, which
would make them shinier on the eventual material.
For the roughness map, I made the decals black
once again to give them sharp reflections (see
Figure 11-34).
With my textures complete, I saved a GIMP .xcf
file with all my layer groups and then exported .tga
files of my diffuse, specular, and roughness maps.

Creating Three Textures
I began with my baked color map in GIMP and
scaled it up to 4096×4096 pixels. Then, I opened my
baked ambient occlusion map as a layer, scaled it to
fit, and set its blend mode to Multiply at 40 percent
opacity in order to add some subtle shadowing to
the texture.
I needed to make three textures: diffuse, rough-
ness, and specular. Because I wanted the body's
green areas to be shiny, I made the green area much
darker for the diffuse texture and bright green for
the specular texture. For the body's white areas, I
did the opposite: dark gray on the specular map to
make it less shiny and light on the diffuse.
For the roughness map, I made the green
areas (of the diffuse map) dark to give sharp, glossy
reflections, and I made the white areas bright to give
softer highlights. You can see the three textures in
Figure 11-34. To keep my textures organized, I cre-
ated separate layer groups for each of the diffuse,
specular, and roughness maps, just as I did for the
Bat Creature.

Adding Decals
To make things a bit more interesting, I decided
to add some decals to the Spider Bot. To make
decals, I drew a few simple designs using 2D curves
in Blender and rendered these in black and white.
Then, I opened these as layers over my existing tex-
ture file in GIMP.

Figure 11-34: Textures for the Spider Bot, from left to right: diffuse, specular, and roughness. I incorporated some decals into the
textures to make them more interesting, making sure to add them to the roughness and specular maps as well.