A hidden line mechanism using overinking

摘要

A spiral spring is computed by repeated application of the transform for rotation about x-axis and shifting along the x-axis. The image is plotted with a slow drying spirit pen on overhead transparency film. The resultant overinking produces an image comprising half a left-handed spring and half a right-handed spring which must be split and half flipped to produce the required result. Images of molluses are produced using a similar technique, with the transform for scaling and rotation.