Author Topic: What amount is each octave scaled down from the last?  (Read 1835 times)

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duke54

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What amount is each octave scaled down from the last?
« on: April 17, 2016, 06:16:42 PM »
In the advanced perlin, is each octave 1/2 the size of the one above it, or does the scaling change between octaves?
If the scaling is always the same then using octaves 1-5 would be identical to using octave 6-10 at the same scale correct?
I'm trying to find a good place to start when creating large landscapes. I mean, I can scale it smaller so I'm using octaves 1-6, or I can scale it larger whereby octaves1,2,3 become so large they really have no affect, and I'm effectively using octaves 4-9. Is there a difference? Or am I just driving myself insane asking questions that should never be asked?

Tangled-Universe

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Re: What amount is each octave scaled down from the last?
« Reply #1 on: May 04, 2016, 02:48:47 AM »
I think you're referring to 'lacunarity' and if I'm correct the advanced perlin allows you to change that?
A lacunarity of 2 (as you describe it with 1/2 the size for each next octave) generally looks somewhat inorganic.
Therefore it's usually a wee bit off 2.

duke54

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Re: What amount is each octave scaled down from the last?
« Reply #2 on: May 04, 2016, 06:04:59 PM »
Wow had no idea about lancularity, thanks!

I attached a scalar to the lancularity input on the advanced perlin, and can now better understand the affects. However, I'm not quite sure this answers the question since I'm still not sure whether each octave is scaled down by the same percentage.

Also, the lancularity input requires a scalar, not an interger, so how does that decimal correspond to the scaling?

It seems to me that a lancularity of 1.0 means the octave is scaled down by 50%, so basically, you can use the scalar input to choose between 0 and 50% decrease in scale for each octave.
« Last Edit: May 04, 2016, 07:29:35 PM by duke54 »

duke54

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Re: What amount is each octave scaled down from the last?
« Reply #3 on: May 04, 2016, 07:16:18 PM »
OK, I've been experimenting for a while, and it looks like lancularity (say that 5 times fast) ultimately defines the total range of detail available in your terrain by setting just how small the smallest octave gets relative to your largest octave. The number of octaves, and the persistance then modify the detail within that provided range. So basically, if you have a wide enough range to start, you really don't need to change the lancularity, you should just be using octaves and persistance. Which is what we are all doing in the first place. Doh! Complete circle, but at least now I know.
« Last Edit: May 04, 2016, 07:28:41 PM by duke54 »