In the noise class for 3d noise, it seems like your code was based off of code that contained a mistake in it. That mistake was later corrected and detailed within a paper on page 13 => https://weber.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
your values of 0.6 should be 0.5
This may be why your function sometimes does not return a value between -1 and 1
In the noise class for 3d noise, it seems like your code was based off of code that contained a mistake in it. That mistake was later corrected and detailed within a paper on page 13 => https://weber.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
your values of 0.6 should be 0.5
This may be why your function sometimes does not return a value between -1 and 1