Pseudorandom number generator for noise

Question

I'm trying to make the Perlin noise algorithm described at http://freespace.virgin.net/hugo.elias/models/m_perlin.htm using Lua. However, it doesn't work properly since Lua doesn't support bitwise operators, which are necessary for the pseudorandom number function on that page. I tried messing around with randomseed() but everything I could come up with just made really bizarre patterns. I need a pseudorandom number generator that will generate numbers between -1 and 1 when given the parameters x, y, and a random seed. Pseudocode is fine.

Thanks!

Answer 1

There have been lua libraries made for this, one I found is: lrandom

It uses the Mersenne Twister algorithm which may suit your needs better.

Answer 2

I don't know of any pure Lua solution for the pseudorandom number issue, but you could try to write the algorithm you mention using some pure Lua bit libraries.

I found these in the Wiki:

• LuaBit is a bitwise operation lib totally written in Lua. The bitwise operations supported are: not, and, or, xor, right shift and left shift. Several utilities: hex to dec, utf8 to usc2 and nokia .nfb to txt.
• BitUtils are bitwise operations implemented entirely in Lua.
• Module Compress Deflate includes bit.numberlua, which implements bitwise operations in pure Lua as numbers.

Answer 3

It is easy to make a linear congruential random number generator in Lua. A simple one is Park-Miller

function pmrng (x) return math.fmod(x * 16807, 2147483647) end

This will give you the next random integer [1..2147483646] after x, the seed. Use this integer to make a float by dividing by the modulus, 2147483647 in this case.

prng_seed = 13579
function upmrng () prng_seed = pmrng(prng_seed); return prng_seed / 2147483647 end

To scale this to -1 .. +1 do

upmrng() * 2 - 1