Not sure how good they are in practice. I just experimented a little bit with it ( https://i.imgur.com/pLyKKpg.png ) and there seem to be a pattern that destroys the uniform line pattern in certain directions (in the lower part), however, with most obstacles it left a lot of stuff behind (the upper part in the picture). The initial pattern is not very simple though: https://i.imgur.com/PfVjVOt.png
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http://en.wikipedia.org/wiki/Gun_%28cellular_automaton%29
https://en.wikipedia.org/wiki/Spacefiller
How good are those?! Led me on to some of the other breeders https://en.wikipedia.org/wiki/Breeder_(cellular_automaton)
Not sure how good they are in practice. I just experimented a little bit with it ( https://i.imgur.com/pLyKKpg.png ) and there seem to be a pattern that destroys the uniform line pattern in certain directions (in the lower part), however, with most obstacles it left a lot of stuff behind (the upper part in the picture). The initial pattern is not very simple though: https://i.imgur.com/PfVjVOt.png