A virtual or computer-generated three-dimensional model allows a user to easily manipulate and/or modify the model and its surrounding environment. Thus, virtual three-dimensional models of physical objects are widely used by professionals, such as animators, architects, designers, engineers and scientists. Virtual three-dimensional models are usually created by measuring physical objects using a contact or non-contact technique to extract spatial information from the physical objects. The spatial information is then processed to render the measured physical objects into virtual three-dimensional models.
Some non-contact measuring techniques involve the use of laser light to measure relative positions of different surface points on a physical object. The relative distance measurements are based on the travel time of laser light. A concern with systems that use laser light for three-dimensional measurements is that timing of the laser light is limited by the switching frequency of the laser light and the delay measurements of the received laser light, which must be extremely precise especially when measuring small objects. Another concern with such systems is that, if the object is highly reflective, such as a metallic object, or is transparent or translucent, the measuring systems may fail or provide unreliable measurements.
Other non-contact measuring techniques involve the use of photos of an object based on parallax to triangulate the relative positions of different surface points on the object. Thus, a precise knowledge of camera position, relative to the object, for each photo is required to solve the triangulation equations with reasonable precision. A concern with systems that use photos for three-dimensional measurements is the resulting measurements are much less precise than the measurements based on laser light. Another concern is that such systems require the surface of an object to have special optical properties. For example, the surface of an object must be such that light must reflect in ways not too different from an ideal model of Lambertian reflections. In addition, the mathematical triangulation problem is ill-defined for large areas of an object with the same color. For instance, due to lack of contrast, it is practically impossible to measure small surface variations in a large white surface using triangulation based on photos.
Contact measuring techniques typically involve the use of a touch-based sensor or stylus to manually contact different surface points of an object to measure the relative positions of the surface points. A concern with systems that use a touch-based sensor is that the surface points are manually measured one point at a time. Consequently, the process of measuring the surface points using such a measuring system requires a significant amount of time.
In view of these concerns, there is a need for a system and method for measuring three-dimensional objects with precision and efficiency.