When a camera is calibrated, it becomes possible to relate the captured images with the outside world. We previously explained that if the 3D structure of an object is known, then one can predict how the object will be imaged on the sensor of the camera. The process of image formation is indeed completely described by the projective equation that was presented at the beginning of this chapter. When most of the terms of this equation are known, then it becomes possible to infer the value of the other elements (2D or 3D) through the observation of some images. In this recipe, we will look at the camera pose recovery problem when a known 3D structure is observed.
Let's consider a simple object, a bench in a park. We took an image of this one using the camera/lens system calibrated in the previous recipe. We also have manually identified eight distinct image points on the bench that we will use for our camera pose estimation:
Having access to this object...