Fig. 8.

Image speeds generated by the perspective transformation of moving objects in a simulated environment. A frustum (red outline) was embedded in a larger spherical space. Point objects (colored dots) moving in randomly assigned directions at randomly assigned speeds entered the frustum volume from the surrounding space and projected onto an image plane (blue outline). The frequency of occurrence of image speeds arising from these objects was determined, thus approximating the empirical link between image speeds and object movements.