Now it's totally silly to have DepthCue_StartDist be anything but 0, at least for underwater attenuation. Unless there is an air bubble around the camera, attenuation begins immediately.

So we're going to set a = 0, and only deal with the end distance, b.

This simplifies our equation a bit. With a = 0, the equation is just:

1 - x/b

In the attached graph, b = 6.

I'd like to introduce another idea here that will be very useful later. This is the notion of "half distance". This is the distance at which the attenuation function is precisely 1/2. The half distance is exactly b/2. In this case, that would be a distance of 3.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)