I'll get the ball rolling with this: I converted Simplex noise written in java to lua and found myself caught on a potential out of bounds error being reported as an attempt to index a nil value. I've commented out most of the code and focused on one point where I could no longer adequately test the problem. I've put a couple days into this, so it's time to put it out there for someone else to look at. It could be obvious to a more experienced author what I'm missing. If you give it a look, you have my gratitude!
Code
--
-- simplex noise proto.lua
-- v.0.0.1 revision and testing
-- generates simplex noise in 2d, 3d and 4d
-- source: https://weber.itn.liu.se/~stegu/simplexnoise/SimplexNoise.java
-- used in filter forge map script component
--[[
Simplex noise is a type of gradient noise that is used for generating natural-looking textures, terrain,
and other procedural content.
A speed-improved simplex noise algorithm for 2D, 3D and 4D in Lua.
Based on example code by Stefan Gustavson (stegu@itn.liu.se).
Optimisations by Peter Eastman (peastman@drizzle.stanford.edu).
Lua conversion by David Bryan Roberson (https://github.com/eyeofparadox) in 2023
Better rank ordering method for 4D by Stefan Gustavson in 2012.
This could be speeded up even further, but it's useful as it is.
Version 2012-03-09-2023
This code was placed in the public domain by its original author,
Stefan Gustavson. You may use it as you see fit, but attribution is appreciated.
--]]
function prepare()
-- inputs and precalculation.
noiseScale = 50
noiseOctaves = 4
noiseLacunarity = 2.0
noisePersistence = 0.5
grad3 = {
{1,1,0},{-1,1,0},{1,-1,0},{-1,-1,0},
{1,0,1},{-1,0,1},{1,0,-1},{-1,0,-1},
{0,1,1},{0,-1,1},{0,1,-1},{0,-1,-1}
}
grad4 = {
{0, 1, 1, 1}, {0, 1, 1, -1}, {0, 1, -1, 1}, {0, 1, -1, -1},
{0, -1, 1, 1}, {0, -1, 1, -1}, {0, -1, -1, 1}, {0, -1, -1, -1},
{1, 0, 1, 1}, {1, 0, 1, -1}, {1, 0, -1, 1}, {1, 0, -1, -1},
{-1, 0, 1, 1}, {-1, 0, 1, -1}, {-1, 0, -1, 1}, {-1, 0, -1, -1},
{1, 1, 0, 1}, {1, 1, 0, -1}, {1, -1, 0, 1}, {1, -1, 0, -1},
{-1, 1, 0, 1}, {-1, 1, 0, -1}, {-1, -1, 0, 1}, {-1, -1, 0, -1},
{1, 1, 1, 0}, {1, 1, -1, 0}, {1, -1, 1, 0}, {1, -1, -1, 0},
{-1, 1, 1, 0}, {-1, 1, -1, 0}, {-1, -1, 1, 0}, {-1, -1, -1, 0}
}
p = {
151,160,137,91,90,15,
131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
190,6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
88,237,149,56,87,174,20,125,136,171,168,68,175,74,165,71,134,139,48,27,166,
77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
102,143,54,65,25,63,161,1,216,80,73,209,76,132,187,208,89,18,169,200,196,
135,130,116,188,159,86,164,100,109,198,173,186,3,64,52,217,226,250,124,123,
5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
223,183,170,213,119,248,152,2,44,154,163,70,221,153,101,155,167,43,172,9,
129,22,39,253,19,98,108,110,79,113,224,232,178,185,112,104,218,246,97,228,
251,34,242,193,238,210,144,12,191,179,162,241,81,51,145,235,249,14,239,107,
49,192,214,31,181,199,106,157,184,84,204,176,115,121,50,45,127,4,150,254,
138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
}
n = #p
perm = {}
-- initialize permutation table with random values
for i=1,256 do
perm[i] = math.random(0,255)
end
-- extend the permutation table to avoid overflow
for i=257,512 do
perm[i] = perm[i - 256]
end
permMod12 = {}
-- initialize permMod12 table with 0 values
for i = 1, 512 do
permMod12[i] = 0
end
for i=1,512 do
permMod12[i] = perm[i] % 12
end
-- update grad3 and grad4 with the new permutation table
-- for i=1,256 do
-- grad3[i+1] = {grad3[perm[i+1] % 12 + 1][1], grad3[perm[i+1] % 12 + 1][2], grad3[perm[i+1] % 12 + 1][3]}
-- grad4[i+1] = {grad4[perm[i+1] % 32 + 1][1], grad4[perm[i+1] % 32 + 1][2], grad4[perm[i+1] % 32 + 1][3], grad4[perm[i+1] % 32 + 1][4]}
-- end
F2 = 0.5*(math.sqrt(3.0)-1.0)
G2 = (3.0-math.sqrt(3.0))/6.0
F3 = 1.0/3.0
G3 = 1.0/6.0
F4 = (math.sqrt(5.0)-1.0)/4.0
G4 = (5.0-math.sqrt(5.0))/20.0
end;
function get_sample(x, y)
if x < 0 or x > 1 or y < 0 or y > 1 then
return 0.5, 0.5, 0.5, 1
end
local xin, yin = x/noiseScale, y/noiseScale
local noise2D = get_2d_noise(xin, yin, noiseOctaves, noiseLacunarity, noisePersistence)
-- local noise3D = 0 -- get_3d_noise(xin, yin, 0, noiseOctaves, noiseLacunarity, noisePersistence)
-- local noise4D = 0 -- get_4d_noise(xin, yin, 0, 0, noiseOctaves, noiseLacunarity, noisePersistence)
local r = noise2D
-- local g = noise3D
-- local b = noise4D
local a = 1
-- return r, g, b, a
return r, 0, 0, a
-- return 0, g, 0, a
-- return 0, 0, b, a
end
function test_variables(r, g, b, a)
local variables = {r, g, b, a}
local nil_values = false
for i=1, 4 do
if variables[i] == nil then
variables[i] = 0
nil_values = true
elseif variables[i] ~= nil then
variables[i] = variables[i]
else
variables[i] = 1
nil_values = true
end
end
if nil_values then
return unpack(variables)
end
end
--[[
function grad3(...)
local args = {...}
for i, x in ipairs(args) do
args[i] = x % n
end
local a = args[1] + args[2] + args[3]
local gi = permMod12[a % n]
-- for i in `grad3`
if grad3[i] == nil then
return 1, 0, 1, 1
end
return dot({grad3[gi][1], grad3[gi][2], grad3[gi][3]}, args[1] - grad3[a % 12 + 1][1], args[2] - grad3[a % 12 + 1][2], args[3] - grad3[a % 12 + 1][3])
end
function grad4(...)
local args = {...}
for i, x in ipairs(args) do
args[i] = x % n
end
local a = args[1] + args[2] + args[3] + args[4]
local gi = permMod12[a % n]
-- for i in `grad4`
if grad4[i] == nil then
return 1, 0, 1, 1
end
return dot({grad4[gi][1], grad4[gi][2], grad4[gi][3], grad4[gi][4]}, args[1] - grad4[a % 32 + 1][1], args[2] - grad4[a % 32 + 1][2], args[3] - grad4[a % 32 + 1][3], args[4] - grad4[a % 32 + 1][4])
end
]]--
function fastfloor(x)
local xi = math.floor(x)
return (x < xi) and (xi-1) or xi
end
function dot(grd, x, y)
return (grd.x*x) + (grd.y*y) -- debug "Script error (line 141) : attempt to index a nil value (local 'grd')" >>> called from: lines 215,222,229
end
-- function dot(grd, x, y, z)
-- return (grd.x*x) + (grd.y*y) + (grd.z*z)
-- end
-- function dot(grd, x, y, z, w)
-- return (grd.x*x) + (grd.y*y) + (grd.z*z) + (grd.w*w)
-- end
function get_2d_noise(xin, yin)
local n0, n1, n2
local s = (xin+yin)*F2
local i = fastfloor(xin+s)
local j = fastfloor(yin+s)
local t = (i+j)*G2
local x0 = i-t
local y0 = j-t
local x0 = xin-x0
local y0 = yin-y0
local i1, j1
if x0>y0 then
i1 = 1
j1 = 0
else
i1 = 0
j1 = 1
end
local x1 = x0 - i1 + G2
local y1 = y0 - j1 + G2
local x2 = x0 - 1.0 + 2.0 * G2
local y2 = y0 - 1.0 + 2.0 * G2
local ii = (i + 1) & 255
local jj = (j + 1) & 255
test_variables(ii,jj)
local gi0 = permMod12[ii+perm[jj]]
local gi1 = permMod12[ii+i1+perm[jj+j1]]
local gi2 = permMod12[ii+1+perm[jj+1]]
test_variables(gi0,gi1,gi2)
local t0 = 0.5 - x0*x0-y0*y0
if t0<0 then
n0 = 0.0
else
t0 = t0 * t0
n0 = t0 * t0 * dot(grad3[gi0], x0, y0) -- <<< grad3[gi0],grad3[gi1],grad3[gi2] may be `nil`: points at lines 206-208 again
end
local t1 = 0.5 - x1*x1-y1*y1
if t1<0 then
n1 = 0.0
else
t1 = t1 * t1
n1 = t1 * t1 * dot(grad3[gi1], x1, y1)
end
local t2 = 0.5 - x2*x2-y2*y2
if t2<0 then
n2 = 0.0
else
t2 = t2 * t2
n2 = t2 * t2 * dot(grad3[gi2], x2, y2)
end
return (n0 + n1 + n2)
-- return 70.0 * (n0 + n1 + n2)
end
--[[
function get_3d_noise(xin, yin, zin)
local n0, n1, n2, n3
local s = (xin+yin+zin)*F3
local i = math.floor(xin+s)
local j = math.floor(yin+s)
local k = math.floor(zin+s)
local t = (i+j+k)*G3
local x0 = i-t
local y0 = j-t
local z0 = k-t
local x0 = xin-x0
local y0 = yin-y0
local z0 = zin-z0
local i1, j1, k1
local i2, j2, k2
if x0>=y0 then
if y0>=z0 then
i1=1; j1=0; k1=0; i2=1; j2=1; k2=0
elseif x0>=z0 then
i1=1; j1=0; k1=0; i2=1; j2=0; k2=1
else
i1=0; j1=0; k1=1; i2=1; j2=0; k2=1
end
else -- x0<y0
if y0<z0 then
i1=0; j1=0; k1=1; i2=0; j2=1; k2=1
elseif x0<z0 then
i1=0; j1=1; k1=0; i2=0; j2=1; k2=1
else
i1=0; j1=1; k1=0; i2=1; j2=1; k2=0
end
end
local x1 = x0 - i1 + G3
local y1 = y0 - j1 + G3
local z1 = z0 - k1 + G3
local x2 = x0 - i2 + 2.0*G3
local y2 = y0 - j2 + 2.0*G3
local z2 = z0 - k2 + 2.0*G3
local x3 = x0 - 1.0 + 3.0*G3
local y3 = y0 - 1.0 + 3.0*G3
local z3 = z0 - 1.0 + 3.0*G3
local ii = (i + 1) & 255
local jj = (j + 1) & 255
local kk = (k + 1) & 255
-- in `get_3d_noise`
if not ii or jj or kk then
return 0, 1, 0, 1
end
-- local gi0 = permMod12[ii+perm[jj+perm[kk+1] ]
local gi1 = permMod12[ii+i1+perm[jj+j1+perm[kk+k1+1] ]
local gi2 = permMod12[ii+i2+perm[jj+j2+perm[kk+k2+1] ]
local gi3 = permMod12[ii+1+perm[jj+1+perm[kk+1+1] ]
local t0 = 0.6 - x0*x0 - y0*y0 - z0*z0
if t0<0 then n0 = 0.0 else
t0 = t0 * t0
n0 = t0 * t0 * dot(grad3[gi0], x0, y0, z0)
end
local t1 = 0.6 - x1*x1 - y1*y1 - z1*z1
if t1<0 then n1 = 0.0 else
t1 = t1 * t1
n1 = t1 * t1 * dot(grad3[gi1], x1, y1, z1)
end
local t2 = 0.6 - x2*x2 - y2*y2 - z2*z2
if t2<0 then n2 = 0.0 else
t2 = t2 * t2
n2 = t2 * t2 * dot(grad3[gi2], x2, y2, z2)
end
local t3 = 0.6 - x3*x3 - y3*y3 - z3*z3
if t3<0 then n3 = 0.0 else
t3 = t3 * t3
n3 = t3 * t3 * dot(grad3[gi3], x3, y3, z3)
end
return 32.0*(n0 + n1 + n2 + n3)
end
function get_4d_noise(x, y, z, w)
local n0, n1, n2, n3, n4
local s = (x + y + z + w) * F4
local i = math.floor(x + s)
local j = math.floor(y + s)
local k = math.floor(z + s)
local l = math.floor(w + s)
local t = (i + j + k + l) * G4
local x0 = i - t -- unskew the cell origin back to (x,y,z,w) space
local y0 = j - t
local z0 = k - t
local w0 = l - t
local x0 = x - x0
local y0 = y - y0
local z0 = z - z0
local w0 = w - w0
local rankx = 0
local ranky = 0
local rankz = 0
local rankw = 0
if x0 > y0 then
rankx = rankx + 1
else
ranky = ranky + 1
end
if x0 > z0 then
rankx = rankx + 1
else
rankz = rankz + 1
end
if x0 > w0 then
rankx = rankx + 1
else
rankw = rankw + 1
end
if y0 > z0 then
ranky = ranky + 1
else
rankz = rankz + 1
end
if y0 > w0 then
ranky = ranky + 1
else
rankw = rankw + 1
end
if z0 > w0 then
rankz = rankz + 1
else
rankw = rankw + 1
end
local i1, j1, k1, l1
local i2, j2, k2, l2
local i3, j3, k3, l3
i1 = (rankx >= 3) and 1 or 0
j1 = (ranky >= 3) and 1 or 0
k1 = (rankz >= 3) and 1 or 0
l1 = (rankw >= 3) and 1 or 0
i2 = (rankx >= 2) and 1 or 0
j2 = (ranky >= 2) and 1 or 0
k2 = (rankz >= 2) and 1 or 0
l2 = (rankw >= 2) and 1 or 0
i3 = (rankx >= 1) and 1 or 0
j3 = (ranky >= 1) and 1 or 0
k3 = (rankz >= 1) and 1 or 0
l3 = (rankw >= 1) and 1 or 0
local x1 = x0 - i1 + G4
local y1 = y0 - j1 + G4
local z1 = z0 - k1 + G4
local w1 = w0 - l1 + G4
local x2 = x0 - i2 + 2.0*G4
local y2 = y0 - j2 + 2.0*G4
local z2 = z0 - k2 + 2.0*G4
local w2 = w0 - l2 + 2.0*G4
local x3 = x0 - i3 + 3.0*G4
local y3 = y0 - j3 + 3.0*G4
local z3 = z0 - k3 + 3.0*G4
local w3 = w0 - l3 + 3.0*G4
local x4 = x0 - 1.0 + 4.0*G4
local y4 = y0 - 1.0 + 4.0*G4
local z4 = z0 - 1.0 + 4.0*G4
local w4 = w0 - 1.0 + 4.0*G4
local ii = (i + 1) & 255
local jj = (j + 1) & 255
local kk = (k + 1) & 255
local ll = (l + 1) & 255
-- in `get_4d_noise`
if not ii or jj or kk or ll then
return 0, 0, 1, 1
end
local gi0 = perm[ii+perm[jj+perm[kk+perm[ll] ] ] ] & 31
local gi1 = perm[ii+i1+perm[jj+j1+perm[kk+k1+perm[ll+l1] ] ] ] & 31
local gi2 = perm[ii+i2+perm[jj+j2+perm[kk+k2+perm[ll+l2] ] ] ] & 31
local gi3 = perm[ii+i3+perm[jj+j3+perm[kk+k3+perm[ll+l3] ] ] ] & 31
local gi4 = perm[ii+1+perm[jj+1+perm[kk+1+perm[ll+1] ] ] ] & 31
local t0 = 0.6 - x0*x0 - y0*y0 - z0*z0 - w0*w0
if t0 < 0 then
n0 = 0.0
else
t0 = t0 * t0
n0 = t0 * t0 * dot(grad4[gi0], x0, y0, z0, w0);
-- n0 = t0 * t0 * (x0 * grad4[gi0].x + y0 * grad4[gi0].y + z0 * grad4[gi0].z + w0 * grad4[gi0].w)
end
local t1 = 0.6 - x1*x1 - y1*y1 - z1*z1 - w1*w1
if t1 < 0 then
n1 = 0.0
else
t1 = t1 * t1
n1 = t1 * t1 * dot(grad4[gi1], x1, y1, z1, w1);
-- n1 = t1 * t1 * (x1 * grad4[gi1].x + y1 * grad4[gi1].y + z1 * grad4[gi1].z + w1 * grad4[gi1].w)
end
local t2 = 0.6 - x2*x2 - y2*y2 - z2*z2 - w2*w2
if t2 < 0 then
n2 = 0.0
else
t2 = t2 * t2
n2 = t2 * t2 * dot(grad4[gi2], x2, y2, z2, w2);
-- n2 = t2 * t2 * (x2 * grad4[gi2].x + y2 * grad4[gi2].y + z2 * grad4[gi2].z + w2 * grad4[gi2].w)
end
local t3 = 0.6 - x3*x3 - y3*y3 - z3*z3 - w3*w3
if t3 < 0 then
n3 = 0.0
else
t3 = t3 * t3
n3 = t3 * t3 * dot(grad4[gi3], x3, y3, z3, w3);
-- n3 = t3 * t3 * (x3 * grad4[gi3].x + y3 * grad4[gi3].y + z3 * grad4[gi3].z + w3 * grad4[gi3].w)
end
local t4 = 0.6 - x4*x4 - y4*y4 - z4*z4 - w4*w4
if t4 < 0 then
n4 = 0.0
else
t4 = t4 * t4
n4 = t4 * t4 * dot(grad4[gi4], x4, y4, z4, w4);
-- n4 = t4 * t4 * (x4 * grad4[gi4].x + y4 * grad4[gi4].y + z4 * grad4[gi4].z + w4 * grad4[gi4].w)
end
return 27.0 * (n0 + n1 + n2 + n3 + n4)
end
]]--
local grad = {
x = 0, y = 0, z = 0, w = 0
}
function grad:new(x, y, z)
local obj = {
x = x, y = y, z = z
}
setmetatable(obj, self)
self.__index = self
return obj
end
function grad:new(x, y, z, w)
local obj = {
x = x, y = y, z = z, w = w
}
setmetatable(obj, self)
self.__index = self
return obj
end
In Filter Forge, where this script is used in a Map Script component, the coordinates x,y exist on an infinite plain though the frame of the image is bound between (0,0),(1,1). Point samples made within those bounds are typically also within the standard range of 0,1 but their r,g,b,a values can go on infinitely in HDR. I suspect the nil value error likely originates from an out-of-bounds access of the perm or permMod12 array, which can occur if the input values for x and y fall outside the expected range of [0, 1]. Revisions were made to compensate but the error just moved upstream until it reached the if at lines 228-233. The tables referenced in lines 222-225 should have been initialized with non nil values, so I wonder where the error could be coming from?
