Chapter 14: Making a Character Model

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In this chapter we are going to build a character model, step by step. We are going to animate it and skin it. It's going to be a long and sometimes hectic ride, so hang on to your hat!

Modeling Techniques

There are many different approaches or techniques that modelers use. The differences can be based on what tools are available to do a given job or what data is available about the item to be modeled. There are other techniques available not described here—that's because we are modeling for games, and low-poly modeling is the philosophy we need to follow. Remember that the more polygons one model uses, the fewer polygons available for other instances of that model, or for other models, in a given rendered frame of a scene at a given frame rate. In games there is that polygon budget to consider.

Shape Primitives

Creating models using shape primitives can be an extremely quick way to build a low-poly model, depending on your expertise and eye for detail. The basic technique involves selecting a primitive that best matches the part of the model you are building. The primitive shape must contain enough polygons and vertices for you to adjust the shape to closely match your target.

This is the technique we are going to use to build our character model in this chapter.

Incremental Polygon Construction

Incremental Polygon Construction is a method that fairly closely approximates modeling with clay in the real world. Sculpting with clay generally involves adding bits of clay together to create shapes that grow in size and detail. The clay can be poked and prodded, smoothed and pinched until it accurately depicts the item being modeled.

With Incremental Polygon Construction, the process is similar: We apply vertices in 3D space that represent high points and low points of the features to be modeled, and then we build triangles or faces connecting these vertices. One point of departure from clay modeling is that we typically don't add faces on top of (such that they completely obscure) other faces, because we have no need for a solid to give us the required volume. But the principle of adding faces to the existing topology of a model as the model grows is the same, as is the useful concept that we add only what we need, and no more.

The best way to get started with modeling in this way is to use photographs or sketches of the target from several directions: from directly in front, directly above, and one or both sides. From the pictures we can obtain the locations and shapes of the features and their high and low points. We mark these points in our 3D views, and then we proceed to build faces from them.

This technique can be quite slow going. It is also prone to errors that are difficult to correct, because you may have moved dozens of steps beyond where the real error occurred before the error becomes evident.

Axial Extrusion

In the simplest sense, you start with a primitive object (usually a box, but it could be a simple facet or triangle), subdivide it, and then select specific polygons to extrude into meshes to form general shapes. When you subdivide objects, you increase the number of polygons on each side of the shape. You then adjust and refine the extruded polygons to form the details of the model. This approach is similar to making models of geographic terrain using a contour map as a guide, with cardboard or plywood sheets to build up the terrain, and then smoothing the edges with some kind of filler.

With Axial Extrusion, you limit your extrusions to one of the three axes— sometimes all three in various combinations—but individual extrusion only occurs in one axis. This technique is usually restricted to inanimate objects, but sometimes certain parts of character models are made this way.

One example of using axial intrusion in character modeling is when creating a head. A series of flat-plane profiles (called cuts) are made of a head, after which each profile is extruded once in each direction on the transverse axis (the axis that runs from ear to ear). Then each extruded mesh is married to the extruded meshes of the adjacent cuts by an averaging of the vertices. You'll actually get to do some of these extrusions later in this chapter, and others.

Arbitrary Extrusion

Arbitrary Extrusion has much in common with Axial Extrusion, except that you extrude your base primitive shapes in whatever directions are necessary. Like Incremental Polygon Construction, this approach to modeling can be seen as similar to sculpting in clay. Machinery lends itself well to modeling with this technique.

Topographical Shape Mapping

Topographical Shape Mapping is a method usually used to model terrain, like Axial Extrusion often is, except that Topographical Shape Mapping is best suited for automated operations rather than manually modeling.

In the geographic sense, topographic data can be obtained from various government and private sources. The data consists of, at a minimum, a coordinate and an altitude for each mapped point on the real terrain's surface. There are various algorithms and many programs available that can read this data from a file and render a 3D view of the terrain in question. The data files come in various formats depending on the agency that produces them: DLG-O, DEM, SDTS, and DRG, to name just a few from that acronymic world. Normally this approach is used in one of the many available Geographic Information Systems (GIS), and there are tools that can convert this data into a format you can use for modeling in games.

Hybrids

Well, the Hybrid category is the catchall category. Often it is prudent to combine techniques in a single model—use the approach that works best for the component being created. If you find yourself mixing techniques, most likely you will be doing a little bit of Incremental Polygon Construction mixed with many shape primitives or using a few primitives mixed with a great deal of Arbitrary Extrusion.

The best point to be made here is that you should use what works best for you in your current circumstances.