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// http://www.iquilezles.org/www/articles/palettes/palettes.htm
// to see this function graphed out go to: https://www.desmos.com/calculator/rz7abjujdj
vec3 cosPalette( float t , vec3 brightness, vec3 contrast, vec3 osc, vec3 phase)
{
return brightness + contrast*cos( 6.28318*(osc*t+phase) );
}
void main() {
vec2 pos = ((gl_FragCoord.xy/resolution) - 0.5)*2.0; // origin is in center
// who remembers SOH CAH TOA ?
// tan, given an angle will return the ratio
// so if we only have the ratio of position
// we use atan to get the angle
float angle = atan(pos.y,pos.x);
float r = sin(angle + time);
// sin returns a number from -1 to 1, and colors are from 0 to 1, so thats
// why you only see red on the screen half the time. the angle goes around
// the screen, adding time moves it clockwise
float ringFrequency = 5.; // making this number bigger will increase frequency
float g = cos(length(pos*ringFrequency) - time);
// the distance (aka length) from the center put in a cos, time moves the
// circles in.
float b = cos(angle+ cos(length(pos*ringFrequency *3.)));
// this combines what we learned in the red and green channels
// angle is going through a cos and so is the length, so we see the
// blue channel oscillating in both dimensions the polar coordinates give us
// please play around with these numbers to get a better palette
vec3 brightness = vec3(0.8);
vec3 contrast = vec3(0.2);
vec3 osc = vec3(r);
vec3 phase = vec3(g, cos(time/23.), sin(time/31.));
vec3 color = cosPalette(b, brightness, contrast, osc, phase);
gl_FragColor = vec4(color,1.);
}
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