Problem with my Perlin Noise implementation?

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Joined: 14 Apr 2019 17:22

Problem with my Perlin Noise implementation?

#1 Post by Lowsun » 09 Jul 2020 17:18

I was interested in procedural generation and tried to implement the perlin noise algorithm in Batch. It seems to work fine in some cases, however there are some really weird spots that just pop out of nowhere. Here is the code that generates a texture. After reading the article, I assumed that there are "cells", and each corner of the cell has a random vector assigned to it. So to create a larger image, the script stitches them together. This is what the parameters mean:

gr[dimensions] is how many characters are in each cell, starting from 0. So gr[dimensions] of 2 is actually 3 characters.

gr[width] is how many cells in length

gr[height] is how many cells in height

All the math is directly taken from ... h-faq.html. I've tried to comment what each part does.

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FOR /F %%A in ('ECHO prompt $E^| cmd') DO SET "ESC=%%A"
(CHCP 65001)>NUL
::gr = gradient, d = dummy, px = pixel
SET /A "gr[dimensions]=2","gr[width]=4","gr[height]=4"

::Other variables needed. gr[itery] and gr[iterx] is how many times to actually iterate
SET /A "gr[width]*=gr[dimensions]","gr[height]*=gr[dimensions]","gr[itery]=gr[height]-gr[dimensions]","gr[iterx]=gr[width]-gr[dimensions]"
SET lerp="a=d[dot1]", "b=d[dot2]", "c=wei[x]", "px[x#]=(10-c)*a+(c*b)"

ECHO Generating...
::Make gradient vectors 
FOR /L %%Y in (0, %gr[dimensions]%, %gr[height]%) DO (
    FOR /L %%X in (0, %gr[dimensions]%, %gr[width]%) DO (
        SET /A "d[x]=!RANDOM!*(2+2+1)/32768-1","d[y]=!RANDOM!*(2+2+1)/32768-2"
        SET "gr[%%X][%%Y]=!d[x]!;!d[y]!"

::starting point of texture to 5 down, 10 right
<NUL SET /P "=%ESC%[2J%ESC%[5;10H"

::loop through and create. the first 2 for loops are to get the randoms vectors, and the inner 2 for loops are for each character
::also, for the final px[final], I do (px[final]*4)+150 for the colour value, since it is pretty small

FOR /L %%Y in (0, %gr[dimensions]%, %gr[itery]%) DO (
    FOR /L %%X in (0, %gr[dimensions]%, %gr[iterx]%) DO (
        SET /A "gr[x]=%%X+gr[dimensions]","gr[y]=%%Y+gr[dimensions]"
        FOR /L %%y in (0, 1, %gr[dimensions]%) DO (
            FOR /L %%x in (0, 1, %gr[dimensions]%) DO (
                %perlin% %%x %%y %%X %%Y !gr[x]! !gr[y]!
                SET /A "px[final]=(px[final]*4)+150"
                <NUL SET /P "=%ESC%[38;2;100;!px[final]!;!px[final]!m█"
            <NUL SET /P "=%ESC%[%gr[dimensions]%D%ESC%[D%ESC%[B"
        <NUL SET /P "=%ESC%[%gr[dimensions]%C%ESC%[C%ESC%[%gr[dimensions]%A%ESC%[A"
    SET /A "d[num]=(gr[dimensions]+1)*((gr[iterx]/gr[dimensions])+1)"
    <NUL SET /P "=%ESC%[!d[num]!D%ESC%[%gr[dimensions]%B%ESC%[B"

::This function returns 2 dot products : x y and the values of gx1 gy1, and x y and the values of gx2 gy2
:DOTPRODUCT <x> <y> <gx1> <gy1> <gx2> <gy2>
FOR /F "tokens=1-4 delims=;" %%A in ("!gr[%3][%4]!;!gr[%5][%6]!") DO (
    SET /A "d[dot1]=((%1-%3)*%%A)+((%2-%4)*%%B)","d[dot2]=((%1-%5)*%%C)+((%2-%6)*%%D)"

SET ^"LF=^

^" Above empty line is required - do not remove
SET ^"\n=^^^%LF%%LF%^%LF%%LF%^^"

::<x> <y> <bx> <by> <nx> <ny>
::this is follows the same steps as the link provided, except the "weight" is just a normal exponential curve
::returns px[final] as the number
SET perlin=FOR %%# in (1, 1, 2) DO IF %%#==2 ( FOR /F "tokens=1-6" %%A in ("^!args^!") DO (%\n%
    SET /A "wei[x]=%%A*%%A","wei[y]=%%B*%%B"%\n%
    CALL :DOTPRODUCT %%A %%B %%C %%D %%E %%D%\n%
    SET /A %lerp:#=1% %\n%
    CALL :DOTPRODUCT %%A %%B %%C %%F %%E %%F%\n%
    SET /A %lerp:#=2% %\n%
    SET /A "a=px[x1]","b=px[x2]", "c=wei[y]", "px[final]=((10-c)*a+(c*b))/100"%\n%
)) else SET args=
This is what it looks like with

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SET /A "gr[dimensions]=3","gr[width]=4","gr[height]=4"

And it looks okay, but sometimes there are some glaring "bright spots" that don't make sense, especially with larger cell numbers. For example, with

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SET /A "gr[dimensions]=12","gr[width]=2","gr[height]=2"

Which is obviously wrong. I'm not exactly sure what I'm doing wrong, except that I know the results are wrong. If anyone has any clues or tips, it'd be really appreciated! Thanks :)

Posts: 50
Joined: 06 May 2020 10:14

Re: Problem with my Perlin Noise implementation?

#2 Post by T3RRY » 10 Jul 2020 04:21

Just though a bit of quick testing, as dimensions increase, the value of px[final] scales to the point it (far) exceeds the 255 value limit of the RGB values hence the washed out colours.

I added the following code to your script to generate the attatched log in order see whats happening with the variable vaules for each cell.
The test was on the parameters: SET /A "gr[dimensions]=12","gr[width]=2","gr[height]=2"

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		>>"%~dp0Outfile.Txt" (
		Set px[
		Set gr[
		Set d[
		Set lerp
I place the above in the nested for loop imediately below the line:

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                <NUL SET /P "=%ESC%[38;2;100;!px[final]!;!px[final]!m█"
(260.01 KiB) Downloaded 13 times

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