Structured Light Scanners
A new technology, structured light scanners, provide a potentially low-cost solution to the problem of higher-priced laser scanning hardware. The tools required for acquiring data using structured light scanners can be as simple and inexpensive as a digital camera and a slide projector, or as elaborate and expensive as a structured light digitizing head and a complicated scanning rig.

What differentiates the technology of structured light scanning from the laser scanning technology is that the light that is read by the software interpreting the changes in the 3D surface is not laser light but standard light that is readily available from a slide projector lamp or some similar white light source, such as a halogen lamp.

[Figures 22 & 23] Individual scans used to complete a scan of a head sculpture, along with the resultant head model, which has been rebuilt and rendered.

3D data from a structured light scanner can be acquired in more than one way. One way is to use multiple cameras that interpret the data using stereovision. Another way is to utilize a single camera and software to extract the 3D information from the pattern of structured light on the physical object.

Structured light scanners typically project a predefined and calibrated light pattern onto the 3D surface of the object to be modeled. The pattern of light is distorted by the variation of the object's surface. The software in the structured light scanning system triangulates the differences in the light pattern on the distorted surface to calculate 3D geometry.

Like some laser scanners, structured light scanners capture complete surfaces from a particular point of view. Multiple passes are made to acquire the data from multiple points of view (Figure 22). These multiple passes are combined into a single, seamless data set using merging software that is usually included with the purchase of the scanning package (Figure 23).

NURBS Surfacing of Polygonal Surfaces
Applying NURBS surfaces to scanned polygonal data sets has become very sophisticated in the last few years. Several software packages can accomplish this task. Some are more successful than others, and some are more expensive than others. These modeling programs use as an input raw scan data. The final output of the software programs is a series of NURBS patches that have parametric alignment and geometric tangency.

Because a lot of cleanup is involved when working with scan data, programs available for creating NURBS surfaces from this data generally include tools that enable the user to clean up the data prior to creating the surfaces. This type of software works by starting with a dense polygonal mesh and uses specialized algorithms to draw a NURBS surface into the details of the scanned data. A modeler witnessing this process for the first time will see an impressive sight. The form and detail of the scan data are transferred to the surface as if by magic. When used correctly, this type of software can create amazingly accurate representations of real-life objects using NURBS surfaces that can be used in animation, manufacturing and design. When the model is complete, it is a fully realized NURBS patch model that has been created in a fraction of the time that it would take to build a patch model by hand.