Dear All,
on YouTube I found a very interesting kind of optical illusion:
​https://youtu.be/1ZjTdOEbOTQ
Only by switching through a (kind of) color spectrum one gets the impression of a directed motion. But in fact nothing is moving!
I could not find any specific information nor even the name of this effect. (Maybe anyone knows?) So I only can make some guess and see if it works: Obviously the figures need to have small rims on both sides, and the colors of rim--figure--rim are chosen according to the spectrum with a mutual shift.
In principle the effect can obviously be demonstrated like so:
In[]:=
(*defininga"spectrum":*)colormap={RGBColor[0.5266402027474895,0.9998839593362644,0.5053767954412822],RGBColor[0.7370712955745226,0.9596101823096218,0.29110634741701785`],RGBColor[0.8782412824173896,0.7586542244155544,0.11349092602512437`],RGBColor[0.9108995810830971,0.46628226871189354`,0.030952714083690384`],RGBColor[0.8431116349582077,0.1908163546642674,0.10819927027886592`],RGBColor[0.6824068709778932,0.030025818397176284`,0.2766403541925564],RGBColor[0.4494850758276679,0.00018904918677005987`,0.4645009285825438],RGBColor[0.23605463425579848`,0.04099673944621803,0.7018135155975465],RGBColor[0.10471407079620926`,0.20910559744433072`,0.8715469310741312],RGBColor[0.05491327618205986,0.5064766527235602,0.9357714191896551],RGBColor[0.15009312486541562`,0.7973546685628036,0.881754059000513],RGBColor[0.3006233957222033,0.9918058827915849,0.7259962409629016]};​​(*threecolorsfor:rim/figure/rim*)​​colShift=3;​​colorTriple[indx_]:={colormap[[Mod[indx-colShift,12,1]]],colormap[[Mod[indx,12,1]]],colormap[[Mod[indx+colShift,12,1]]]}​​rimShift=.03;​​disk[{c1_,c2_,c3_}]:={c1,Translate[Disk[],{-rimShift,-rimShift}],c3,Translate[Disk[],{rimShift,rimShift}],c2,Disk[]};​​Manipulate[Graphics[disk[colorTriple[n]],Background->Lighter[Gray,0.5]],{n,1,12,1},SaveDefinitionsTrue]
Out[]=
​
n
Next I tried to make several disks “move”:
In[]:=
disk[pt:{x_,y_},dir:{vx_,vy_},{c1_,c2_,c3_}]:={c1,Translate[Disk[pt],-dir],c3,Translate[Disk[pt],dir],c2,Disk[pt]};​​rimShift=.05;​​ptdir=Table[With[{xx=Cos[n2Pi/12.],yy=Sin[n2Pi/12.]},{5{xx,yy},rimShift{yy,-xx}}],{n,0,11}];​​Manipulate[Graphics[disk[#1,#2,colorTriple[n]]&@@@ptdir,Background->Lighter[Gray,0.5]],{n,1,48,1},SaveDefinitionsTrue]
Out[]=
​
n
Finally I was curious to see if something more meaningful could be done, e.g. the demonstration of a flow by a vector field (see above):
vField[x_,y_]:={y^2,y^2-x^2};​​vgr=VectorPlot[vField[x,y],{x,-3,3},{y,-3,3},VectorMarkers->"Dart",ImageSize->Large,VectorColorFunction->None,VectorStyle->Black,VectorSizes->Automatic,VectorAspectRatio->1/2];​​arrowPolygs=Cases[vgr,Polygon[__],All];​​​​mvPoly[poly_Polygon,{c1_,c2_,c3_}]:=Module[{dir},dir=0.015Normalize[vField@@(Mean@@poly)];​​{c1,Translate[poly,dir],c3,Translate[poly,-dir],c2,poly}];​​​​imgList=Table[Image@Graphics[mvPoly[#,colorTriple[n]]&/@arrowPolygs,ImageSize->700,Background->Lighter[Gray,0.5]],{n,1,12}];​​​​Animate[imgList[[n]],{n,1,12,1},DefaultDuration->0.7,SaveDefinitionsTrue]​​​​(*toexportasgif:*)​​(*SetDirectory[NotebookDirectory[]];​​Export["vectors.gif",imgList,"DisplayDurations"->0.05]*)
Out[]=
n
But doing this in a purely empirical way is quite unsatisfying - the basic questions are:
​
is there an optimal “color palette/spectrum/background”?
what are the best mutual distances of the respective picked colors (above: colShift)?
how big these colored rims should be (above: rimShift)?
I hope you enjoyed this little demo, best regards -- Henrik

CITE THIS NOTEBOOK

Optical illusion of motion based on change of colors​
​by Henrik Schachner​
Wolfram Community, STAFF PICKS, June 1, 2022
​https://community.wolfram.com/groups/-/m/t/2542031