checkpoint_beat_TheForce.glsl

float getBPMVis(float bpm){
    
        // this function can be found graphed out here :https://www.desmos.com/calculator/rx86e6ymw7
	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;
}