/*
 * SinusPlasma
 * An oldschool demo effect, reborn
 * Left click to change gradient colors, right click to change plasma curve
 *
 * Joerg Reuter, jore[at]stachelig[dot]de
 * Creative Commons Attribution 3.0 license
 * http://stachelig.de
 */

// global parameters ... feel free to tweak
// effect is largely tied to screen size, because of the simplistic plasma function
// drop me an e-mail for an improved version that renders to a OpenGL texture and scales it up

int SCREENWIDTH  = 640;
int SCREENHEIGHT = 360;

int GRADIENTLEN = 1500;
// use this factor to make things faster, esp. for high resolutions
int SPEEDUP = 3;

// swing/wave function parameters
int SWINGLEN = GRADIENTLEN*3;
int SWINGMAX = GRADIENTLEN / 2 - 1;

// gradient & swing curve arrays
private int[] colorGrad;
private int[] swingCurve;

// create standard gradient & swing curve
void setup() {
	size(SCREENWIDTH, SCREENHEIGHT, P2D);
	makeGradient(GRADIENTLEN);
	makeSwingCurve(SWINGLEN, SWINGMAX);
}

// draw one frame of the sinus plasma
void draw() {
	loadPixels();
	int i = 0;
	int t = frameCount*SPEEDUP;
	int swingT = swing(t); // swingT/-Y/-YT variables are used for a little tuning ...

	for (int y = 0; y < SCREENHEIGHT; y++) {
		int swingY  = swing(y);
		int swingYT = swing(y + t);
		for (int x = 0; x < SCREENWIDTH; x++) {
			// this is where the magic happens: map x, y, t around
			// the swing curves and lookup a color from the gradient
			// the "formula" was found by a lot of experimentation
			pixels[i++] = gradient(
					swing(swing(x + swingT) + swingYT) +
					swing(swing(x + t     ) + swingY ));
		}
	}
	updatePixels();
}

// create a new random gradient when mouse is pressed
void mousePressed() {
	if (mouseButton == LEFT)
		makeGradient(GRADIENTLEN);
	else if (mouseButton == RIGHT)
		makeSwingCurve(SWINGLEN, SWINGMAX);
}
  
// fill the given array with a nice swingin' curve
// three cos waves are layered together for that
// the wave "wraps" smoothly around, uh, if you know what i mean ;-)
void makeSwingCurve(int arrlen, int maxval) {
	// default values will be used upon first call
	int factor1=2;
	int factor2=3;
	int factor3=6;

	if (swingCurve == null) {
		swingCurve = new int[SWINGLEN];
	} else {
		factor1=(int) random(1, 7);
		factor2=(int) random(1, 7);
		factor3=(int) random(1, 7);
	}

	int halfmax = maxval/factor1;

	for( int i=0; i<arrlen; i++ ) {
		float ni = i*TWO_PI/arrlen; // ni goes [0..TWO_PI] -> one complete cos wave
		swingCurve[i]=(int)(
			cos( ni*factor1 ) *
			cos( ni*factor2 ) *
			cos( ni*factor3 ) *
			halfmax + halfmax );
	}
}

// create a smooth, colorful gradient by cosinus curves in the RGB channels
private void makeGradient(int arrlen) {
	// default values will be used upon first call
	int rf = 4;
	int gf = 2;
	int bf = 1;
	int rd = 0;
	int gd = arrlen / gf;
	int bd = arrlen / bf / 2;

	if (colorGrad == null) {
		// first call
		colorGrad = new int[GRADIENTLEN];
	} else {
		// we are called again: random gradient
		rf = (int) random(1, 5);
		gf = (int) random(1, 5);
		bf = (int) random(1, 5);
		rd = (int) random(0, arrlen);
		gd = (int) random(0, arrlen);
		bd = (int) random(0, arrlen);
		System.out.println("Gradient factors("+rf+","+gf+","+bf+"), displacement("+rd+","+gd+","+bd+")");
	}

	// fill gradient array
	for (int i = 0; i < arrlen; i++) {
		int r = cos256(arrlen / rf, i + rd);
		int g = cos256(arrlen / gf, i + gd);
		int b = cos256(arrlen / bf, i + bd);
		colorGrad[i] = color(r, g, b);
	}
}

// helper: get cosinus sample normalized to 0..255
private int cos256(final int amplitude, final int x) {
	return (int) (cos(x * TWO_PI / amplitude) * 127 + 127);
}

// helper: get a swing curve sample
private int swing(final int i) {
	return swingCurve[i % SWINGLEN];
}

// helper: get a gradient sample
private int gradient(final int i) {
	return colorGrad[i % GRADIENTLEN];
}