Optical illusions

[sometimes99er]

And here's an XB version ... 😉
 

100 call screen(15)::call clear::call magnify(3)::display at(12,15):"+";
110 call char(36,"030F1F3F7F7FFFFFFFFF7F7F3F1F0F03C0F0F8FCFEFEFFFFFFFFFEFEFCF8F0C")
120 for i=1 to 16::call sprite(#i,36,14,85+sin(i/2.55)*70,124+cos(i/2.55)*70)::next i
130 for i=1 to 16::call color(#i,1)::for j=1 to 30::next j::call color(#i,14)::next i::goto 130
run

 

[Reciprocating Bill]

"Circle Illusion," fbForth. All objects moving on the screen are moving in straight lines.  

 

 

 

[+Lee Stewart]

On 9/15/2022 at 3:23 PM, TheBF said:

I saw this today on Twitter and it shocked the hell out of me so I had to make one.

It would be simple in XB. 

 

Perhaps stating the obvious to this group, but the illusion is caused by retinal fatigue. When staring at a single-colored object that is replaced by white or neutral space, the retina will perceive the complementary color of the missing object for a short time. The complementary color of magenta is green. The apparent, moving ball would be red were the ball colors cyan and blue were they yellow.

 

...lee

[Zoyous]

1 hour ago, Reciprocating Bill said:

"Circle Illusion," fbForth. All objects moving on the screen are moving in straight lines.  

 

 

 

That's cool. I remember seeing a diagram of an aircraft engine with the cylinders moving in a similar way; essentially everything moving linearly but resulting in a circular motion array.

[sometimes99er]

Wobbly ...
 

100 call screen(2)::a$=rpt$("0",25)::a$="C08"&a$&"80C00301"&a$&"103"::call char(64,a$,72,a$,80,a$,88,a$)
110 a$="@RHZ@RHJPBXJPBXZ"::a$=a$&a$::b$="ACYKQCYKQSI[ASI["::b$=b$&b$::call clear
120 for i=1 to 11::display at(i*2,1):a$::display at(i*2+1,1):b$::a$=seg$(a$,31,2)&seg$(a$,1,30)
130 b$=seg$(b$,31,2)&seg$(b$,1,30)::next i::call hchar(24,3,32,4)::call color(1,2,2,5,16,14,6,2,12,7,2,14,8,16,12)
140 goto 140
run

 

[+mizapf]

On 9/19/2022 at 4:33 PM, Lee Stewart said:

Perhaps stating the obvious to this group, but the illusion is caused by retinal fatigue. When staring at a single-colored object that is replaced by white or neutral space, the retina will perceive the complementary color of the missing object for a short time.

This is why I simply cannot bear these "dark modes" on displays or some web sites where you have a very dark or black backdrop, and bright letters. Honestly, I have afterimages for more than half a minute, dark blurry lines where I previously saw the bright text lines.

[PeteE]

100 call clear::call screen(16)::call magnify(4)::call char(32,"CCCCCCCCCCCCCCCC")::c=5::s=3
110 call char(88,"0000000000000000000000000000000000000000000000000000FCFCFCFCFFFF")
120 call char(92,"000003030F0F3F3FFFFF000000000000FCFCFCFCFCFCFCFCFCFCC0C0C0C0C0F0")
130 call char(96,"7F7F0000000000000000000000000000FFFF0000000000000000000000000000")
140 for i=0 to 3
150 call sprite(#i*2+1,88,c,i*24+1,i*64+18,0,s,#i*2+2,92,c,33+i*24,i*64+16,0,s,#i+9,96,c,150+i*10,i*64+64,0,s)
160 next i
170 call color(1,2,16)::for i=0 to 2000::next i
180 call color(1,16,16)::for i=0 to 1000::next i::goto 170
run

Pigeon neck illusion, inspired by this

Edited January 28 by PeteE
call color faster than call char