# Globes within Spirals? (Optical Art Tutorial)

Are you seeing spirals? Look again, they’re actually concentric circles! This unique variation of the “Fraser spiral” plays tricks on your eyes by blending a regular line pattern (representing the circle’s circumference) with misaligned elements (the spheres with varying brightness).

Would you like to learn how to create this mesmerizing illusion? Follow my simple visual tutorial. If you have any ideas to further enhance this project, please don’t hesitate to reach out.

This optical art can seamlessly fit into any merchandise venture.

You can find prints and canvases of this artwork on my online gallery. Just in case, here are the codes for those who are familiar with Shadertoy:

```void mainImage( out vec4 O, vec2 u )
{
vec2  R = iResolution.xy,
U = ( u+u - R ) / R.y;                       // normalized coordinates
float l = length(U), y = l, a = atan(U.y,U.x), n = 48./6.28, // polar coords
L = round(log(l)*8.), A = round(a*n);        // (L,A) : disc id
l = exp(L/8.);                               // (l,A/n): disc pos (polar)
l -= sign( mod(A-L,2.) - 1. ) *l/60.;              // offset 1 disc /2 to suggest spiral
U = 60.*( U/l - cos( A/n - vec2(0,1.57)) );        // disc local coords
y = 60.*( y/l - 1. );                              // local radial coord
mod(A-L,4.) < 2. ? y = -y : y;                     // disc gradient direction
l = length(U) - 2.5;                               // disc SDF
O = vec4( mix( .5, fract(y/5.5+.5), smoothstep( 1., -1., l/fwidth(l) ) )); // draw disc
}```