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pakt23

See /software/p5js/pakt-februari/pakt23/ for a JavaScript version and /software/supercollider/februari-pakt/pakt23/ for accompanying sound code.

#include "cinder/app/App.h"
#include "cinder/cairo/Cairo.h"

using namespace ci;
using namespace ci::app;
using namespace std;

const int WIDTH= 640;
const int HEIGHT= 480;

class pakt23App : public App {
public:
    void setup();
    void draw();
    cairo::SurfaceImage srfOff;
    cairo::Context ctxOff;
    int index;
    float w, h;
    int n;
};

void pakt23App::setup() {
    srfOff= cairo::SurfaceImage(WIDTH, HEIGHT, false);
    ctxOff= cairo::Context(srfOff);
    ctxOff.setSourceRgba(1, 1, 1, 0.02);
    ctxOff.paint();
    ctxOff.setLineWidth(1);
    index= 0;
    w= getWindowWidth();
    h= getWindowHeight();
    n= 250;
}

void pakt23App::draw() {
    
    float rx= sin(index*0.0024f);
    float ry= sin(index*0.0022f+1.0f);
    float tx= sin(index*0.0016f+2.0f)+rx;
    float ty= sin(index*0.0018f+3.0f)+ry;
    
    cairo::Context ctx(cairo::createWindowSurface());
    ctxOff.setSourceRgba(1, 1, 1, 0.02);
    ctxOff.paint();
    
    ctxOff.moveTo(w*0.5f, h*0.5f);
    for(int i= 50; i<n; i++) {
        float t= float(i)/n;
        if(i==50) {
            ctxOff.moveTo((cos(t*M_PI*2*rx*tx)*0.495f*t+0.5f)*w, (sin(t*M_PI*2*ry*ty)*0.495f*t+0.5f)*h);
        } else {
            float c= sin(t*M_PI*2)*0.5f+0.5f;
            ctxOff.setSourceRgba(c, 0.0, 0.0, c);
            ctxOff.lineTo((sin(t*M_PI*2*rx*tx)*0.495f*t+0.5f)*w, (cos(t*M_PI*2*ry*ty)*0.495f*t+0.5f)*h);
            ctxOff.lineTo((cos(t*M_PI*2*rx*tx)*0.495f*t+0.5f)*w, (sin(t*M_PI*2*ry*ty)*0.495f*t+0.5f)*h);
            ctxOff.stroke();
        }
    }
    index++;
    ctx.copySurface(srfOff, srfOff.getBounds());
}

CINDER_APP(pakt23App, Renderer2d, [&]( App::Settings *settings ) {
    settings->setWindowSize( WIDTH, HEIGHT );
    settings->setResizable( false );
})