Tuesday night, I was a bit stressed and tired from my day, and I looked for a way to relax. So, doing some code in G’MIC 
My tortuous mind wondered what it would be like to rotate a polygon and at the same time have it move along a random spline-like trajectory. Yes, it sounds like a silly idea, but I had a feeling it might turn out something cool.
I have to say that the first results obtained were a little beyond my expectations, so I decided to dig a little deeper and it’s with great pleasure that I can present to you today a new filter in G’MIC-Qt, named Rendering / Spline Spirograph, which allows you to do just that:
The filter looks like this when called from the plug-in:
As always when I’m doing this kind of experiment, I was amazed by the fact that the code didn’t take that long to write (prototyping with G’MIC is so cool 
). And that’s going to benefit potentially a lot of people right away. Time well spent
Here is the full source code for this new filter (56 lines of code, don’t tell me it’s too long! ).
Code for "Spline Spirograph" filter
#@gui Spline Spirograph : fx_spline_spirograph, fx_spline_spirograph
#@gui : Seed = int(0,0,65535)
#@gui : Randomize Seed = button()
#@gui : sep = separator()
#@gui : Complexity (%) = float(50,0,100)
#@gui : Sampling (%) = float(100,0,100)
#@gui : Radius (%) = float(20,0,100)
#@gui : Vertices = int(3,2,16)
#@gui : Twist = float(20,0,150)
#@gui : Offset (deg.) = float(0,-180,180)
#@gui : sep = separator()
#@gui : Colors = choice(3,"Default","HSV","Lines","Hot","Cool","Jet","Flag","Cube","Rainbow","Parula","Spring",\
# "Summer","Autumn","Winter","Bone","Copper","Pink","VGA","Algae","Amp","Balance","Curl","Deep","Delta","Dense","Diff",\
# "Gray","Haline","Ice","Matter","Oxy","Phase","Rain","Solar","Speed","Tarn","Tempo","Thermal","Topo","Turbid",\
# "Aurora","Hocuspocus","SRB2","Uzebox","Amiga7800","Amiga7800mess","Fornaxvoid1")
#@gui : Alpha Channel = bool(0)
#@gui : sep = separator()
#@gui : Normalization Strength (%) = float(50,0,100)
#@gui : Normalization Radius (%) = float(50,0,100)
#@gui : sep = separator()
#@gui : note = note("<small>Author: <i>David Tschumperlé</i>. Latest Update: <i>2024/04/10</i>.</small>")
fx_spline_spirograph :
seed,randomize_seed,complexity,sampling,radius,vertices,twist,\
offset,colors,is_alpha,normalization_strength,normalization_radius=${1-12}
if $randomize_seed seed:=v(65535) fi
foreach {
nm={n}
if $is_alpha to_a else remove_opacity fi
f 0 => canvas
palette $colors r. 360,1,1,3,3 to_colormode. {0,s} => palette
# Parameterization of a random spline curve.
rs[canvas] 100,100,-1,2 ${}
srand $seed noise_poissondisk. {max(5,lerp(100,0,$complexity%^0.3))}
0 eval.. "i?da_push([u,x*w#$canvas%,y*h#$canvas%])" da_freeze. rm..
sort. +,y channels. 1,2
r. 1,{max(1,h*max(w#0,h#0)*($sampling%)^2)},1,2,5 => coords
# Draw spirograph along spline.
eval[coords] ":
const R = $radius%*max(w#$canvas,h#$canvas);
const N = $vertices;
C = round(I);
pP = [ 0,0 ];
repeat (N + (N>2),k,
ang = ($offset + lerp(0,360,k/N) + y*360*$twist/h)%360;
P = round(C + R*cexp([0,ang°]));
k>0?polygon(#$canvas,2,pP,P,-1,I(#$palette,ang,0,0,1));
pP = P;
)"
k[canvas]
n 0,255 normalize_local {10*$normalization_strength%},{max(1,($normalization_radius%)^3*10*max(w,h)%)}
}
u \{$seed\}\{0\}\{$density\}\{$radius\}\{$vertices\}\{$twist\}\{$offset\}\{$colors\}\
\{$normalization_strength\}\{$normalization_radius\}
That’s all I had to say.
Feel free to play with it and post your own exciting results!
Cheers.
(I’m lovin’ those 2 random buttons 
)
