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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.

 

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