public static void plotDirectedHalfPlane(FPoint2 p0, FPoint2 p1, int markType) {
    double SEP = .4 * V.getScale();
    double ang = MyMath.polarAngle(p0, p1);
    FPoint2 d0 = MyMath.ptOnCircle(p0, ang + Math.PI / 2, SEP);
    FPoint2 d1 = MyMath.ptOnCircle(p1, ang + Math.PI / 2, SEP);

    EdSegment.plotDirectedLine(p0, p1);
    V.pushStroke(STRK_RUBBERBAND);
    V.drawLine(d0, d1);
    V.popStroke();

    if (markType >= 0) {
      V.mark(d0, markType);
      V.mark(d1, markType);
    }
  }
  private static void renderHull(PtEntry pt) {
    Inf inf = Inf.create();
    int count = 30;
    PtEntry ptStart = pt;
    do {
      inf.update();
      if (pt.prev(true) != null) {
        boolean valley = false;

        valley =
            (pt.prev(true).source() == pt.source() && pt.prev(true).orig().next(true) != pt.orig());

        V.pushColor(MyColor.cBLUE);
        V.pushStroke(valley ? STRK_RUBBERBAND : STRK_THICK);
        V.drawLine(pt.prev(true), pt);
        V.pop(2);
      }
      V.pushColor(MyColor.cDARKGREEN);
      V.mark(pt, MARK_DISC, .6);
      V.pop();
      if (Editor.withLabels(true)) {
        StringBuilder sb = new StringBuilder();
        sb.append(" #" + pt.id());
        if (pt.source() != null) sb.append(" <" + pt.source() + ">");

        V.pushScale(.6);
        V.draw(sb.toString(), MyMath.ptOnCircle(pt, MyMath.radians(30), 3), TX_FRAME | TX_BGND);
        V.pop();
      }
      pt = pt.next(true);
      if (count-- == 0) V.draw("too many points rendering!", 50, 50, TX_CLAMP);
    } while (pt != ptStart && count > 0);
  }
 private static String tr(FPoint2 rayStart, double theta) {
   return tl(rayStart, MyMath.ptOnCircle(rayStart, theta, 20));
 }