The process of shooting rays from the eye to the light source to render an image is sometimes called "backwards ray tracing", since it is the opposite direction photons actually travel. However, there is confusion with this terminology. Early ray tracing was always done from the eye, and early researchers such as James Arvo used the term "backwards ray tracing" to mean shooting rays from the lights and gathering the results. Therefore, it is clearer to distinguish "eye-based" versus "light-based" ray tracing.