Yellowtail by Golan Levin (www.flong.com)

Click, drag, and release to create a kinetic gesture.

Yellowtail (1998-2000) is an interactive software system for the gestural creation and performance of real-time abstract animation. Yellowtail repeats a user's strokes end-over-end, enabling simultaneous specification of a line's shape and quality of movement. Each line repeats according to its own period, producing an ever-changing and responsive display of lively, worm-like textures.

import processing.opengl.*;

Gesture gestureArray[];
final int nGestures = 36;  // Number of gestures
final int minMove = 3;     // Minimum travel for a new point
int currentGestureID;

Polygon tempP;
int tmpXp[];
int tmpYp[];


void setup() {
  size(640, 480, OPENGL);
  background(0, 0, 0);
  noStroke();

  currentGestureID = -1;
  gestureArray = new Gesture[nGestures];
  for (int i = 0; i < nGestures; i++) {
    gestureArray[i] = new Gesture(width, height);
  }
  clearGestures();
}


void draw() {
  background(0);

  updateGeometry();
  fill(255, 255, 245);
  for (int i = 0; i < nGestures; i++) {
    renderGesture(gestureArray[i], width, height);
  }
}

void mousePressed() {
  currentGestureID = (currentGestureID+1) % nGestures;
  Gesture G = gestureArray[currentGestureID];
  G.clear();
  G.clearPolys();
  G.addPoint(mouseX, mouseY);
}


void mouseDragged() {
  if (currentGestureID >= 0) {
    Gesture G = gestureArray[currentGestureID];
    if (G.distToLast(mouseX, mouseY) > minMove) {
      G.addPoint(mouseX, mouseY);
      G.smooth();
      G.compile();
    }
  }
}


void keyPressed() {
  if (key == '+' || key == '=') {
    if (currentGestureID >= 0) {
      float th = gestureArray[currentGestureID].thickness;
      gestureArray[currentGestureID].thickness = min(96, th+1);
      gestureArray[currentGestureID].compile();
    }
  } else if (key == '-') {
    if (currentGestureID >= 0) {
      float th = gestureArray[currentGestureID].thickness;
      gestureArray[currentGestureID].thickness = max(2, th-1);
      gestureArray[currentGestureID].compile();
    }
  } else if (key == ' ') {
    clearGestures();
  }
}


void renderGesture(Gesture gesture, int w, int h) {
  if (gesture.exists) {
    if (gesture.nPolys > 0) {
      Polygon polygons[] = gesture.polygons;
      int crosses[] = gesture.crosses;

      int xpts[];
      int ypts[];
      Polygon p;
      int cr;

      beginShape(QUADS);
      int gnp = gesture.nPolys;
      for (int i=0; i<gnp; i++) {

        p = polygons[i];
        xpts = p.xpoints;
        ypts = p.ypoints;

        vertex(xpts[0], ypts[0]);
        vertex(xpts[1], ypts[1]);
        vertex(xpts[2], ypts[2]);
        vertex(xpts[3], ypts[3]);

        if ((cr = crosses[i]) > 0) {
          if ((cr & 3)>0) {
            vertex(xpts[0]+w, ypts[0]);
            vertex(xpts[1]+w, ypts[1]);
            vertex(xpts[2]+w, ypts[2]);
            vertex(xpts[3]+w, ypts[3]);

            vertex(xpts[0]-w, ypts[0]);
            vertex(xpts[1]-w, ypts[1]);
            vertex(xpts[2]-w, ypts[2]);
            vertex(xpts[3]-w, ypts[3]);
          }
          if ((cr & 12)>0) {
            vertex(xpts[0], ypts[0]+h);
            vertex(xpts[1], ypts[1]+h);
            vertex(xpts[2], ypts[2]+h);
            vertex(xpts[3], ypts[3]+h);

            vertex(xpts[0], ypts[0]-h);
            vertex(xpts[1], ypts[1]-h);
            vertex(xpts[2], ypts[2]-h);
            vertex(xpts[3], ypts[3]-h);
          }

          // I have knowingly retained the small flaw of not
          // completely dealing with the corner conditions
          // (the case in which both of the above are true).
        }
      }
      endShape();
    }
  }
}


private void updateGeometry() {
  Gesture J;
  for (int g=0; g<nGestures; g++) {
    if ((J=gestureArray[g]).exists) {
      if (g!=currentGestureID) {
        advanceGesture(J);
      } else if (!mousePressed) {
        advanceGesture(J);
      }
    }
  }
}


void advanceGesture(Gesture gesture) {
  // move a Gesture one step
  if (gesture.exists) { // check
    int nPts = gesture.nPoints;
    int nPts1 = nPts-1;
    Vec3f path[];
    float jx = gesture.jumpDx;
    float jy = gesture.jumpDy;

    if (nPts > 0) {
      path = gesture.path;
      for (int i=nPts1; i>0; i--) {
        path[i].x = path[i-1].x;
        path[i].y = path[i-1].y;
      }
      path[0].x = path[nPts1].x - jx;
      path[0].y = path[nPts1].y - jy;
      gesture.compile();
    }
  }
}

void clearGestures() {
  for (int i=0; i<nGestures; i++) {
    gestureArray[i].clear();
  }
}