Tutorial:
Making a Polygon Head
Low polygon modeling
is also an easy way to create a human head, perhaps for a
real-time game. Starting with a primitive cube, you can add
vertices and edges until you end up with a head similar to
the one in Figure 7.29.
Figure
7.29 The completed polygonal face.
1.
Get a Cube.
Start with
a primitive cube. Enter POL mode and choose the Polygon->Vertex
command with the middle mouse button to add vertices
to the middle of the edges on the front face. Then use
the Polygon->Edge command to connect the four vertices
(you'll have to add one more to the line that bisects
the head) to divide the head into four equal quadrants
(see Figure 7.30).
The face
will lie below the middle line, with the vertical division
as the center of the nose.
Figure
7.30 The bisected cube.
2.
Add the Facial Features.
Add more
vertices and edges to form the eyes, nose, and mouth
as shown in the Figure 7.31. Because the face is largely
symmetrical, facial features can be easily roughed in
by bisecting each line and adding a new vertex at the
midpoint of lines with the Polygon->Vertex command
and the middle mouse button.
Ignore
the top two quadrants, which will become rounded as
the forehead and hair later.
Figure
7.31 A simple face on the cube.
3.
Give the Nose and Chin Depth.
The facial
features all currently lie in a single plane. Some,
such as the nose, need to extend from the face, while
the eyes need to recess.
Tag the
nose point and translate it in Z forward to make the
nose poke out. You can also tag and scale the points
on either side of the nose to make it less broad and
geometric.
Add a new
vertex under the nose, and connect it side to side with
two new edges.
The points
in the center of the head under the nose extending to
the chin can be tagged and translated in Z to create
a chin, and the points on the side of the head can be
translated in Z and scaled inward in X to round the
face.
4.
Make the Eyes.
Select
the eyes with the G supra key and duplicate them. Scale
them down in X and Z to make a smaller polygon for the
eye ball, and translate it slightly in Y to recess it
into the face. The eyeballs are now triangular but could
be more round, so add a few a new vertices to the middle
of each edge and translate all the vertices with the
M supra key to make a rounder eyeball.
With these
new rounder eyeballs selected, duplicate them and scale
them smaller in X and Z to make the irises (see Figure
7.32).
Figure
7.32 The face takes shape with depth
and eyes.
5.
Shape the Skull Shape.
The head
is currently very square, so tag the bottom rear points
and bring them in to make a jaw line. You can also tag
and scale the points on the top of the head in X and
Z a bit to round the shape of the head.
Finally
tag the top points and the rear points (no points on
the face), and choose the Effect]Rounding command. Set
the Round to 0.25 (25% of the line width between points),
and execute the command to see the finished face.
There you have
it: A simple, painless, low poly face (mine has 69 polygons),
suitable for VRML, simulation, or 3D game building (see Figure
7.33). The completed head, in different stages of construction,
can be found on the courseware CD-ROM, in a scene entitled
"polyface."
Figure
7.33 A completed head shape and low
poly face.
Rounding and
Beveling
One side effect
of modeling with polygons is that you tend to create models
with sharp edges. Other times, if you create shapes that should
be rounded, you will see facets when the final is rendered,
which doesn't look good. The Bevel and Rounding tools can
help you smooth the edges of objects after they have been
made.
The Bevel tool,
located in the Model module in the Effect menu cell, adds
one polygon between each edge, effectively rounding the sharp
edges by adding detail (see Figure 7.34). This command can
even be performed locally on tagged vertices only, if you
are in TAG mode. The size of the bevel in Softimage units
can be set in the Bevel dialog box that opens when you choose
the Effect->Bevel command. Although this tool seems like
it’s designed to bevel the edges of text, it can be used
to round any polygonal object.
Figure
7.34 The Bevel dialog box.
The Effect->Rounding
tool performs a similar function, but where the Bevel tool
places the new edges a given distance away from the old edges,
Rounding subdivides each polygon, giving you the option of
deciding how evenly the subdivision is made (see Figure 7.35).
Setting Rounding to 1 divides each polygon exactly in half
and places the new polygons exactly midway between their neighbors
in location and angle. Setting Rounding to 0.5 divides the
previous polygon into two, one-half the size of the other
(see Figure 7.36).
Figure
7.35 The Round dialog box.
Figure
7.36 The effects of beveling and rounding.
Subdivision
Many times in
Polygon modeling you wish you had more detail on an object,
even if just temporarily, so that you can deform the object
more cleanly, or perhaps to work on some of the new, smaller
polygons to add in detail. The manual method of adding vertices
and edges would take a long while if, for instance, you wanted
to add 500 new polygons to the sides of a building to model
the exterior shape.
The Effect->Subdivision
tool, however, takes care of adding new polygonal detail for
you. When you execute the command, a dialog pops up allowing
you to choose how many additional subdivisions will be created
on your model in each axis (see Figure 7.37). Leaving an axis
at 0 does not subdivide the model in that direction at all,
while a subdivision of 1 adds a new edge exactly in the center
of the object.
Figure
7.37 The Polygon Subdivision dialog
box.
For instance,
if you start with a primitive cube with six sides and six
polygons, and use Subdivision on it with a setting of 3 in
X, 3 in Y, and 3 in Z, the cube is divided in thirds in each
axis, resulting in a cube with six faces but 27 polygons.
Subdivision does not change the actual shape of the object
at all; it just adds more polygons by chopping the current
polygons into smaller pieces. You can then manipulate each
of the smaller pieces to add in surface detail to the model.
Cleanup
The Cleanup command
is a complement to the Subdivision command, because it can
remove unneeded polygonal detail from a model. After you use
Subdivide to add in windows and ledges to a building, for
example, you could use Effect]Cleanup to get rid of all the
excess polygons that remain in the model, keeping only those
that add detail.
Cleanup does
this by examining the edge between each pair of polygons in
the model, looking at the angle between the two. If the angle
is 0, then the two polygons are coplanar, and there is no
detail being added by that edge, so it is removed, creating
one larger polygon where two smaller polygons once were.
You can set the
angle at which the Cleanup command decides to get rid of the
edge, by entering an angle in the "Merge polygons if
angle smaller than" entry box.
If, while removing
edges, any vertices are left without any connecting edges,
those vertices are removed. By removing both edges and vertices,
this tool also performs a simple method of polygon reduction,
and should be the first tool you reach for when your models
need to lose weight.
The Cleanup tool
can also merge vertices that are close together, which welds
and cleans slightly inaccurate vertex placement. It can improve
model fidelity from some lower-end, less polygon-accurate
programs, such as 3D Studio.
Unconnected vertices
can be connected, also improving model fidelity, and the new
polygons can be reordered, making the model more orderly and
more likely to work well with other effects.
