Photogrammetry is the use of a two-dimensional (2D) image or images, such as a photograph, to allow a person to analyze the image in order to make accurate measurements of size and orientation of the objects in the image in terms of the original three-dimensional (3D) space. The process allows a person to make measurements of the height, width, and depth of objects in a photograph or similar 2D image, which can then be used to re-create the objects to scale in 3D space. With 3D photogrammetry, the application is used to take images of objects, such as photographs, and re-create the original object as a 3D computer model, typically for use in computer animation or similar applications.
This technique is almost as old as photography itself and was used with some of the earliest daguerreotype images captured. With advancements in computers and technology, however, the process became simpler as computers could handle many of the technical aspects of photogrammetry and make the necessary calculations based on the 2D images. This allowed 3D photogrammetry to become more practical and has led to a number of commercial uses for the technology.
3D photogrammetry is basically a modern application of the original concept. Rather than simply make calculations to understand the size of an object, for purely mathematical or geometric reasons, the measurements are used to create a 3D model of the object. This can be done for use in advertisements, films, or a number of other potential applications. For example, a car commercial may feature images of a car driving through a pristine environment that seems too perfect for the real world but far too accurate for computer generated imagery (CGI).
This is because it is a combination of both the real and CGI. Rather than create a 3D model of the car and buildings around it through traditional CGI modeling techniques, 3D photogrammetry can be used to allow incredibly realistic models to be created. This is because computer software can take images of the car, the buildings around it, and any other parts of the environment in the image, and make precise measurements of every line, angle, and dimension of the objects.
3D photogrammetry can even be used in creating textures for the models, so that the texture mapping is also based on the original photographs, creating ultra-realistic models and textures. Due to the typically very high polygon count of models made through this method, 3D photogrammetry is seldom used for applications such as video games. For realistic applications such as advertising and film special effects, however, the technique is often perfect for allowing relatively easy creation of photorealistic 3D images.