In his book, The
Armchair Universe, computer scientist A.K. Dewdney reprints 5 Easy Pieces, one of his Computer Recreations columns published
in Scientific American. The first easy piece was to program a moving, segmented
caterpillar.
I first programmed this easy piece in the BASIC programming language. In BASIC, the coordinates
of each segment were stored in a 1-dimensional array. To compute the next cycle, the new position for the head was
computed and then every segment was moved up one element of the array. Only one
new movement computation had to be made per cycle of animation!
In Scratch, I used the point
towards block to simplify the animation.
Here’s a screenshot of showing how the caterpillar
starts in 11 segments.
The segments soon fit loosely together since they are
all travelling at the same speed but after a few reflections off the sides, the
segments fit together as is shown in this screenshot.
The project can be viewed and downloaded by clicking on
this link.
http://scratch.mit.edu/projects/353820/
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