CODEWITHSUNDEEP
haskellnoiseperlin-noise
fayong lin
fayong lin

Reputation: 224

integer to noise function in Haskell

I am trying to implement a basic perlin noise function (I know there is a library that does just that, I just want to try my own), and I have some problem with the integer to noise function used to generate deterministic noise from integer inputs.

the function I am trying to implement is defined there: http://libnoise.sourceforge.net/noisegen/index.html#continuousnoise

and my code so far look like this:

noise2d :: (Int32, Int32) -> Double
noise2d (x, y) =
    let m = x + y * 57
        n = (shiftR m 13) ^ m
        j = (n * (n * n * 15731 + 789221) + 1376312589) .&. 0x7fffffff
    in  1.0 - (fromIntegral j / 1073741824.0)

the code compile but I get the same result for any input, due to the fact that n is evaluated to 0.

Is there a better way to do that?

Upvotes: 1

Views: 237

Answers (2)

josejuan
josejuan

Reputation: 9566

Your error is

n = (shiftR m 13) `xor` m
                  ^^^^^

(Instead of the power function (^))

Upvotes: 3

Martin Huschenbett
Martin Huschenbett

Reputation: 568

The problem stems from your use of the ^-operator. In C it is bitwise exclusive disjunction (xor), whereas in Haskell it is exponentiation. So, you just need to change the fourth line to

        n = (shiftR m 13) `xor` m

and everything should be fine.

Upvotes: 5

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