apply2 method

void apply2(Bone parent, Bone child, double targetX, double targetY, int bendDir, double alpha,)

Implementation

void apply2(Bone parent, Bone child, double targetX, double targetY,
    int bendDir, double alpha) {
  if (alpha == 0) {
    child.updateWorldTransform();
    return;
  }
  if (!parent.appliedValid) parent.updateAppliedTransform();
  if (!child.appliedValid) child.updateAppliedTransform();
  final double px = parent.ax, py = parent.ay;
  double psx = parent.ascaleX, psy = parent.ascaleY, csx = child.ascaleX;
  int os1 = 0, os2 = 0, s2 = 0;
  if (psx < 0) {
    psx = -psx;
    os1 = 180;
    s2 = -1;
  } else {
    os1 = 0;
    s2 = 1;
  }
  if (psy < 0) {
    psy = -psy;
    s2 = -s2;
  }
  if (csx < 0) {
    csx = -csx;
    os2 = 180;
  } else {
    os2 = 0;
  }
  final double cx = child.ax;
  double cy = 0.0,
      cwx = 0.0,
      cwy = 0.0,
      a = parent.a,
      b = parent.b,
      c = parent.c,
      d = parent.d;
  final bool u = (psx - psy).abs() <= 0.0001;
  if (!u) {
    cy = 0.0;
    cwx = a * cx + parent.worldX;
    cwy = c * cx + parent.worldY;
  } else {
    cy = child.ay;
    cwx = a * cx + b * cy + parent.worldX;
    cwy = c * cx + d * cy + parent.worldY;
  }
  final Bone pp = parent.parent!;
  a = pp.a;
  b = pp.b;
  c = pp.c;
  d = pp.d;
  final double id = 1 / (a * d - b * c);
  double x = targetX - pp.worldX, y = targetY - pp.worldY;
  final double tx = (x * d - y * b) * id - px, ty = (y * a - x * c) * id - py;
  x = cwx - pp.worldX;
  y = cwy - pp.worldY;
  final double dx = (x * d - y * b) * id - px, dy = (y * a - x * c) * id - py;
  final double l1 = math.sqrt(dx * dx + dy * dy);
  double l2 = child.data.length * csx, a1 = 0.0, a2 = 0.0;
  outer:
  if (u) {
    l2 *= psx;
    double cos = (tx * tx + ty * ty - l1 * l1 - l2 * l2) / (2 * l1 * l2);
    if (cos < -1) {
      cos = -1.0;
    } else if (cos > 1) {
      cos = 1.0;
    }
    a2 = math.acos(cos) * bendDir;
    a = l1 + l2 * cos;
    b = l2 * math.sin(a2);
    a1 = math.atan2(ty * a - tx * b, tx * a + ty * b);
  } else {
    a = psx * l2;
    b = psy * l2;
    final double aa = a * a,
        bb = b * b,
        dd = tx * tx + ty * ty,
        ta = math.atan2(ty, tx);
    c = bb * l1 * l1 + aa * dd - aa * bb;
    final double c1 = -2 * bb * l1, c2 = bb - aa;
    d = c1 * c1 - 4 * c2 * c;
    if (d >= 0) {
      double q = math.sqrt(d);
      if (c1 < 0) q = -q;
      q = -(c1 + q) / 2;
      final double r0 = q / c2, r1 = c / q;
      final double r = r0.abs() < r1.abs() ? r0 : r1;
      if (r * r <= dd) {
        y = math.sqrt(dd - r * r) * bendDir;
        a1 = ta - math.atan2(y, r);
        a2 = math.atan2(y / psy, (r - l1) / psx);
        break outer;
      }
    }
    double minAngle = math.pi,
        minX = l1 - a,
        minDist = minX * minX,
        minY = 0.0;
    double maxAngle = 0.0, maxX = l1 + a, maxDist = maxX * maxX, maxY = 0.0;
    c = -a * l1 / (aa - bb);
    if (c >= -1 && c <= 1) {
      c = math.acos(c);
      x = a * math.cos(c) + l1;
      y = b * math.sin(c);
      d = x * x + y * y;
      if (d < minDist) {
        minAngle = c;
        minDist = d;
        minX = x;
        minY = y;
      }
      if (d > maxDist) {
        maxAngle = c;
        maxDist = d;
        maxX = x;
        maxY = y;
      }
    }
    if (dd <= (minDist + maxDist) / 2) {
      a1 = ta - math.atan2(minY * bendDir, minX);
      a2 = minAngle * bendDir;
    } else {
      a1 = ta - math.atan2(maxY * bendDir, maxX);
      a2 = maxAngle * bendDir;
    }
  }
  final double os = math.atan2(cy, cx) * s2;
  double rotation = parent.arotation;
  a1 = (a1 - os) * MathUtils.radDeg + os1 - rotation;
  if (a1 > 180) {
    a1 -= 360;
  } else if (a1 < -180) {
    a1 += 360;
  }
  parent.updateWorldTransformWith(px, py, rotation + a1 * alpha,
      parent.ascaleX, parent.ascaleY, 0.0, 0.0);
  rotation = child.arotation;
  a2 = ((a2 + os) * MathUtils.radDeg - child.ashearX) * s2 + os2 - rotation;
  if (a2 > 180) {
    a2 -= 360;
  } else if (a2 < -180) {
    a2 += 360;
  }
  child.updateWorldTransformWith(cx, cy, rotation + a2 * alpha, child.ascaleX,
      child.ascaleY, child.ashearX, child.ashearY);
}