Image-source relationships derived from a virtual environment. A) A simulated visual space (red outline) embedded in a larger spherical environment; objects (e.g., ball or a rod) that enter the visual space project onto the image plane (blue outline). Since the 3-D speed, direction and size of every object is known, the statistical relationship between objects and their projections can be determined. (B) Example of a template used to sample the image plane. In this example the template would be applied repeatedly to all regions of the image plane to determine the frequency of occurrence of the speeds of projected sequences moving in different directions over a distance of 2 degrees. By accumulating such data over many different distances, human experience with projected speeds and directions in relation to their sources can be approximated. (After Wojtach et al., 2008)