Photographic miniatures have long been a staple of visual effects, using real-world materials to match the look of a full-sized object. The recent innovations in computer graphics imagery (CGI) has expanded the palette of the visual effects artist into realms that were previously impossible. Three-dimensional, or 3-D, computer graphics are created entirely in the “virtual” world using specialized 3-D software. Though the computer monitor, like the movie screen, is only a two-dimensional medium, geometric data is represented in a three-dimensional construct, using shadows, highlights, and perspective, among other aspects. But whether it's a plastic model on a stick or a computer-generated landscape, the basic steps remain the same.

Modeling Basics

Creating realistic miniatures is a true balance of art and technology. For decades, models were built from clay, metal, wood, rubber, or plastic. They not only had to look real, they often had to operate like the real thing. Propellers had to spin and lights had to blink and power lines had to blow up.

Sometimes even the term “miniature” seems out of place when you consider that models such as the submarines in The Hunt for Red October or the overturned fuel truck in Terminator 2: Judgment Day were each several yards long. Models of cities often take up an entire soundstage, but it's their large size that allows them to be so convincingly detailed. Using a computer, 3-D models can be built “full size” since there's no limit to the size of the imaginary place in which they're constructed. Every 3-D application uses slightly different tools or construction metaphors, but the techniques usually come down to one of four methods.

Solid Geometry

Objects are pieced together from smaller objects, comparable to adding shapes of clay to one another. In their most basic form, the objects are cubes, spheres, cones, pyramids, and prisms.

Polygonal Models

Shapes are defined by the arrangement of polygons along the surface. Usually the polygon is a simple flat triangle. Multiple triangles placed side by side form edges or curves, like a geodesic dome. The smaller the polygon, the smoother the surface. Perhaps a more familiar example would be a soccer ball, which is a sphere made up of several five-sided polygons. Keep in mind, the more polygons you have, the better your object will look, but it will also take up more computer-processing power. Try to find a compromise where it looks good and your computer won't crash.

Subdivided Surfaces

This is defined as the limit of an infinite refinement process. Basically, it means you can begin with a rather blocky shape made up of big subdivisions. You can divide those into smaller subdivisions, then smaller again, and so on. With each successive refinement, the surface of the object becomes smoother. But like polygons, the more subdivisions you have, the more computer power it will take.

NURBS

An acronym for non-uniform rational B-spline, NURBS is a way of expressing complex curves in a standardized mathematical formula. This is important if you're the designer of a car or boat and you want the builders to get the shape just right, but you don't need to understand the math in order to use the NURBS function in most 3-D software. There are usually metaphorical tools to let you shape objects the way you want while the computer handles the number crunching.

Finessing Your Model

Once a model is built, the next step is to add texture, color, shading, transparency, reflectivity, specularity, or any of the seemingly endless list of characteristics that would make an object appear real. Many 3-D applications have built-in surfaces. To make the bumper of a car shine, for example, you only have to highlight the appropriate parts of the object and then select “chrome” from the preset choices. Once the basics are set, you may want to add scratches, dirt, or “rough spots” to add an extra layer of realism.

Building the model may also involve giving the object a skeleton. This is a collection of rigs that, though invisible in the final product, will make it easier to control movement and shape if the object is to be animated. For those who prefer to film models but not build them, several companies and individuals offer completed 3-D models for sale, usually via the Internet. While the prices may seem steep at first, when compared to the time spent building the model, they are usually quite reasonable.