Texture Painting - Blender Master Class: A Hands-on Guide to Modeling, Sculpting, Materials, and Rendering - page 156

it much easier to create textures as nondestructively
as possible, building up one layer and then adding
details in a new layer over the top.
The ability to work in layers also allows you to
combine baked textures with your hand-painted
textures easily. For example, you can add an ambi-
ent occlusion texture over another layer of your tex-
ture map to add shadowing. GIMP also has a more
advanced brush system, making it easier to paint
detailed textures. (I covered the basics of painting
in GIMP in Chapter 2, so we'll cover only the more
texturing-specific aspects of GIMP in this chapter.)

Figure 11-3: The image we'll be using as our brush
texture

Creating Brushes for Texturing in GIMP
GIMP's brushes are easy to edit and are capable of
creating a wide variety of looks. When texturing, it
can often be useful to create custom brushes that
aid in quickly building up texture. In particular,
when used as clone brushes or as paintbrushes,
brushes with a speckled or grungy look are often
useful in blending between different colors and
textures.
For example, let's create a grungy-looking
brush that will come in handy when texturing the
Jungle Temple. Its effect can be seen on the right
of Figure 11-5. To create it, we start with a photo
texture from CGTextures ( http://cgtextures.com/ )
and then refine it into a brush that can be exported
as a default GIMP brush, which can be used again
and again for texturing or painting in GIMP.
GIMP brushes are image files that are used to
control the shape of a brush. RGB (color) images
are used as is (more like a stamp than a brush) and
will not inherit the brush color. Black-and-white
images interpret black as the shape of the brush and
white as transparent, and they take their color from
the color you have selected in GIMP's color picker.
To create a GIMP brush, all we have to do is create a
black-and-white image and save it in one of GIMP's
brush formats ( .gbr or .gih— I'll discuss the differ-
ence between these in a second).

2. Next, identify a square area that might make

a good brush and select that area with the
Rectangular Select tool ( R ; press and hold
shift while dragging to make a square selec-
tion). Copy this area ( ctrl -C) and paste it as
a new image ( ctrl ‑ shift -V), which you'll soon
save as a new brush.

3. While you've already desaturated the image,

it's still encoded using RGB colors, so switch
to using black and white values with Image 4
Mode 4 Grayscale .

4. Next, make a few tweaks to the new image,

painting out some of the splatter that clips the
edge of the canvas. The texture is now ready to
save, as shown in Figure 11-4.

1. Start with a photo of some paint splatter from

CGTextures (see Figure 11-3) and choose
Colors 4 Desaturate to convert the image to
black and white, selecting the Luminosity
option for desaturating the image in order to
give more variation in brightness.

Figure 11-4: A portion of the photo, copied
and pasted into a new image and tweaked
a little around the edges