DPath+width bend not ending at 90 degrees

Comments

• RawrRanger

  July 2023

  Hi jviram
  maybe line end extension can provide the result you need

  the pink part is with end extension
  
• jviram

  July 2023

  Hi RawrRanger, thank you for your suggestion.

  The end result is actually somewhat similar to how I have solved this issue so far. I am "manually" adding a point to the list of points, with no variation X, so that the ending angle is at a perfect 90 degree (and it seems to work).

  However, I cannot extend the limit of the bend further than the last point of the path, so I was looking for a way to modify the ending angle of the polygon. Worst case I can just modify the last point instead of adding another, but I feel I am thinking way too much in terms of what python can do, and was wondering if there was a way to handle it through Klayout's functions and tools specifically. Without adding more points or changing the dimensions of the bend, I mean.
• Matthias

  July 2023 edited July 2023

  @jviram If you want the line end to be perfect 90 degree, you need to make sure the last segment (the line between the second-last and the last point) is exactly vertical. The end cap is constructed perpendicular to the last segment ("S" in the picture below).

  To achieve this, you can approximate the arc by tangents (outer approximation).

  In addition, the last segment has to be long enough, so the inner side segment ("I" in the picture) does not vanish. This implies a minimum segment length or a maximum resolution of the arc which depends on the width of the path.

  

  Matthias
• dick_freebird

  July 2023

  Is there anything in all this, that depends on the "end type" setting
  in the path creation? Obviously not "round", but maybe "square" vs
  "flush"?

  And then of course the whole Python-script vs menu-pick question,
  for which I've got the usual nuthin'.

  
• RawrRanger

  July 2023

  Hi jviram

  if you don't mind to brute force the line end by pcell, here's an example:
  left side is a path w/o forcing 90 deg
  right side is a path w/ forcing 90 deg
  **increase arc points can improve the smoothness of the arc.

  

  import pya
  import math
  
  class RightAnglePath(pya.PCellDeclarationHelper):
    def __init__(self):
      super(RightAnglePath, self).__init__()
      self.param("path",         self.TypeLayer,   "Layer",                default = pya.LayerInfo(0, 0))
      self.param("lineWidth",    self.TypeDouble,  "Line width",           default =   4)
      self.param("roundRadius",  self.TypeDouble,  "Path round radius",    default =   10)
      self.param("roundPoints",  self.TypeInt,     "Path round points",    default =   6)
      self.param("bruteForce90", self.TypeBoolean, "Force end Direction ", default =   True)
  
    def display_text_impl(self):
      return "RightAnglePath"
  
    def coerce_parameters_impl(self):
      pass
  
    def can_create_from_shape_impl(self):
      return self.shape.is_box() or self.shape.is_polygon() or self.shape.is_path()
  
    def parameters_from_shape_impl(self):
      self.r = self.shape.bbox().width() * self.layout.dbu / 2
      self.l = self.layout.get_info(self.layer)
  
    def transformation_from_shape_impl(self):
      return pya.Trans(self.shape.bbox().center())
  
    def arc(self, r, p, bruteForce):
      pts  = []
      for i in range(int(p + 1)):
          a = (90 / p * i)/180 * math.pi
          pts.append(pya.DPoint(r * math.cos(a), r * math.sin(a)))
  
      if bruteForce:
          pts[ 1].x = r
          pts[-2].y = r
      return pts  
  
    def produce_impl(self):
      path = pya.DPath(self.arc(self.roundRadius, self.roundPoints, self.bruteForce90), self.lineWidth)
      self.cell.shapes(self.path_layer).insert(path)
  
  
  class temp(pya.Library):
    def __init__(self):
      self.layout().register_pcell("RightAnglePath", RightAnglePath())
      self.description = "temp"
      self.register("temp")
  temp()
  
  
• jviram

  July 2023

  Hey!

  Thank you all for your input, it seems I was not too far off with what I was trying. I finally achieved the proper angle thanks to your insight @Matthias, as apparently I was managing to crush the "I" segment and thus not achieving the expected result.

  Also, the code snippet was a blessing, @RawrAngel, as I had not thought of modifying the individual DPoints and was modifying the DPoint list, which ended up being a messier solution. Everything is far more readable now, and I could check I was doing things right.

  Best regards!
• jiunnweiyeh

  July 2023

  Hi jviram,
  I just can make some simple code , and here was my code for drawing path.

  viewed_cell.shapes(new_layer).insert(RBA::DPath.new(draw_path_points,pathwidth,(pathwidth / 2.0),(pathwidth / 2.0),1)) 
  

  draw_path_points is what the points list in your path.
  pathwidth means what the width of path.
  as this code , Klayout will create a path with "round" ending.
  Hope that can help you...:)
• dick_freebird

  July 2023

  You have Round, Square, Flush and Variable extension
  options in the Path popup. Square will make you a clean
  end, but past where you click. Flush is what gives non-
  ortho straight angles, where you click. No idea what is
  Variable trying to do or why I'd want it - makes its own
  kind of ugly ends, is what I see.

  Probably the best bet is to make Square the default, and
  learn to "stretch to finish" after stopping the path ortho-clean.
  No idea whether you could control the extension "stick-out"
  to make it need less touchup (like, if stickout is less than min
  metal then maybe you just touch the target edge with the
  path final coord, and extension just overlaps a bit and all
  good.