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Last active July 5, 2020 18:58
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float getBPMVis(float bpm){
// this function can be found graphed out here :
float bps = 60./bpm; // beats per second
float bpmVis = tan((time*PI)/bps);
// multiply it by PI so that tan has a regular spike every 1 instead of PI
// divide by the beat per second so there are that many spikes per second
bpmVis = clamp(bpmVis,0.,10.);
// tan goes to infinity so lets clamp it at 10
bpmVis = abs(bpmVis)/20.;
// tan goes up and down but we only want it to go up
// (so it looks like a spike) so we take the absolute value
// dividing by 20 makes the tan function more spiking than smoothly going
// up and down, check out the desmos link to see what i mean
bpmVis = 1.+(bpmVis*0.05);
// we want to multiply by this number, but its too big
// by itself (it would be too stroby) so we want the number to multiply
// by to be between 1.0 and 1.05 so its a subtle effect
return bpmVis;
void main() {
vec2 pos = uv(); // 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/abs(pos.x+0.01));
// we take the absolute value of x and add a small number to avoid
// dividing by zero which is undefined behavior
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 bpmVis = getBPMVis(128.);
float ringFrequency = 5.; // making this number bigger will increase frequency
float g = cos(length(pos*ringFrequency *bpmVis) - time);
// the distance (aka length) from the center put in a cos, time moves the
// circles in.
float b = cos(angle+ cos(length(pos*15.)) + bands.y * 5.);
// 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
// here the music effects the place where the phase of the cosine starts
vec4 color = vec4(r,g,b,1);
gl_FragColor = color;
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