Create several looping sequences of different lengths (i.e. 17 frames, 25 frames, 38 frames) and let them 'argue' over the value to which a single DMX channel from the lighting dimmer should be set. With some experimentation, you can product an almost infinitely variable, dramatic effect. And then you can do the same thing for each of your flames, with different loop sizes, so that no two will look alike. A similar effect can be used for fireflies.
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