folding prism walk thing

fold.pde

void setup() {
  size(500, 500, P3D);
  frameRate(25);
  blendMode(ADD);
  ortho();
}

void draw() {
  background(0);
  noFill();
  stroke(0, 255, 255, 127);
  strokeWeight(5);
  translate(width / 2, height * 0.7);
  rotateX(-PI / 6);
  rotateY(PI / 3);
  
  float rad = 100;
  PVector maxy = new PVector(0, 0);
  
  float ang = (-frameCount * 2 * PI * 0.05) / 3;
  
  PVector[] v = new PVector[3];
      
  for (int i = 0; i != v.length; ++i) {
    float angle = ((2 * PI * i) / 3) + ang;
    float x = sin(angle) * rad;
    float y = cos(angle) * rad;
    maxy = y > maxy.y ? new PVector(x, y) : maxy;
    v[i] = new PVector(x, y);
  }
  
  translate(0, -maxy.y);
  
  beginShape(TRIANGLES);
  for (int i = 0; i != v.length; ++i) vertex(v[i].x, v[i].y, rad);
  for (int i = 0; i != v.length; ++i) vertex(v[i].x, v[i].y, -rad);
  endShape();
  
  for(int i = 0; i != v.length; ++i) line(v[i].x, v[i].y, rad, v[i].x, v[i].y, -rad);
  
  int segs = 10;
  float extra = 2 * cos(PI / 6) * rad;
  for (int i = 1; i != segs; ++i) {
    line(maxy.x + extra * i, maxy.y, rad, maxy.x + extra * i, maxy.y, -rad);
  }
  line(maxy.x, maxy.y, rad, maxy.x + segs * extra, maxy.y, rad);
  line(maxy.x, maxy.y, -rad, maxy.x + segs * extra, maxy.y, -rad);
  
  saveFrame("###-fold.png");
}