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Comments on Lecture 16 "Impossible Motion"

Comment 1. How can we treat the horizontal lines at the foot of the spade mark?"

In the first figure, the foot of the spade mark contains two horizontal lines, and hence we cannot establish a one-to-one corespondence between the boundary points of the heart and those of the spade. So we cannot apply the ambiguous object construction method directly to this pair of figures.

To overcome this difficulty, we can modify the horizontal lines into slightly slanted lines, as shown in the second figure. In this figure the modification of the horizontal lines is shown in an exaggerated manner. In actual design, we need to change the direction of the lines only very slightly, so that the one-to-one corespondence can be established and still the modification is invisible.

Comment 2. Figures used in the lecture

In this lecture we used many figures in order to explain the method for designing an ambiguous object through the figure constructin process. For those who want to review the process, we post the set of figures for designing ambiguous object "Rectangle and Triangle." 　