There are
many approaches to modeling hair.
In fact, it becomes even more confusing
when one considers all the different
hair styles that people wear.
Normally,
your choices are dictated by the type
of software that you are using. If
it implements pixel shaders that render
fur and hair then you can make a more
realistic hairdo. Pixel shaders are
programs which process pixels. These
generators can be used to perform
mathematical operations that render
fur and hair.
If your software
does not have this ability then you
will most likely have to do some creative
texturing and/or model a hair object(s).
Transparency mapping makes the hair
object appear as if it is made up
of many hair strands. The first set
of instructions explain how to make
hair from objects rather than a hair
generator.
Hair
Object(s) Steps
Fig.
7-27 Object hair step
1. Creating the hair
model from long flattened
cylindrical shapes.
Fig.
7-28 Step 2. Painting
a UV color hair map
and an alpha map for
transparency mapping.
Fig.
7-29 Step 3. Specifying
the UV map for the hair
object.
Step
1 (Figure 7-27). Make
long flattened cylindrical
objects and place them
on the head as if they
were really fat hair strands.
Be sure to overlap them.
Give the object one texture
name.
Step
2 (Figure 7-28). Create
a color image map that
has thin vertical lines.
Make another transparency
map image from the original
that is white where the
color strands are and
black in the spaces between
them.
Step
3 (Figure 7-29). Make
a UV map of the hair object
and apply both the transparency
and color map as the UV
hair texture.
Figure
7-30 shows a rendering
of the same female wearing
a hair object with transparency
mapping and hair made
from a pixel shader.
Fig.
7-30 Two different methods
for creating hair. The female
on the left has hair made
from an object that is transparency
mapped while the one on the
right is wearing a wig made
with a hair generator.
Hair
Generator Guide Steps
If
your software has a hair generator
or plug-ins available then you can
use the following instructions to
make long hair guides. Your hair generator
can then use these guides to create
more hairs. Even though this tutorial
shows how to make ponytail hairstyle,
you might still be able to utilize
the information to create whatever
hairdo you want.
Fig.
7-31 Pixel shader hair
step 1. Making the first
three strands for the
bangs.
Fig.
7-32 Step 2. Duplicating
and distributing the
hair groups across the
forehead.
Step
1 (Figure 7-31). Create
a spline that sticks into
the scalp a little bit
and whose end sticks out
and hangs down over the
forehead. This short strand
of hair has approximately
7 vertices. Make 2 duplicates
of the hair strand and
arrange them similarly
to the illustration.
Step
2 (Figure 7-32). Duplicate
the 3 hair splines and
place them next to the
first set. Continue copying,
pasting, and placing the
set of 3 hairs until they
are arranged around the
forehead. It is important
to always have the first
point of each spline inside
the scalp.
Step
3 (Figure 7-33). Hide
all the hair splines except
for the top ones that
run across the forehead.
Start on one end, select
each corresponding point
and create a spline that
connects across these
vertices. Do the same
for all the other points
until you have a mesh
of vertical and horizontal
splines.
Step
4 (Figure 7-34). Hide
this mesh and connect
the middle vertical splines.
Finally connect the splines
that are closest to the
head. You should now have
3 sets of connected splines.
Fig.
7-34 Step 4. The
3 groups of hair
meshes after connecting
each set of splines.
Fig.
7-35 Step 5. Deleting
the vertical splines
except for those
at the beginning
of the forehead.
These are rail
cloned across
the horizontal
splines.
Fig.
7-36 Step 6. Rail
cloned guides
for the bangs.
Fig.
7-37 Step 7. The
guides are jittered
and brought together
at the ends.
Fig.
7-33 Step 3. Connecting
the corresponding
hair splines.
Step
5 (Figure 7-35).
The horizontal splines
that were the result
of connecting the
vertical ones will
now be used as the
rails when performing
a rail clone. A
rail clone is an
operation that duplicates
splines and polygons
across a given path
such as a spline(s).
Delete all the original
vertical splines
except for the ones
at the side and
beginning of the
forehead. Place
the horizontal splines
(the rails) in a
background layer.
Step
6 (Figure 7-36).
Rail clone the 3
vertical splines.
For segments pick
length, make the
clone uniform, type
80 for the amount
of strands, and
turn off oriented
and scaling. If
80 yields too many
hair strands, you
can always cut back
on the amount.
Step
7 (Figure 7-37).
Right now the hair
strands are too
even so they need
to be jittered a
little bit. Bring
the ends of the
hair together so
that groups appear
to bunch up.
Step
8 (Figure 7-38).
Now it is time to
make the hair that
runs across the
scalp toward the
back. The beginning
overlaps into the
bangs and ends where
the ponytail will
begin. Create 3
sets of splines
that run the length
of the head. The
3rd spline is the
one that is furthest
from the scalp.
Duplicate the set
of 3 splines and
distribute each
group around the
head. Make sure
the beginning of
each spline is inside
the scalp.
Fig.
7-38 Step 8. New sets, each
consisting of 3 hair guides,
are created across the scalp.
These lead toward the ponytail.
