How to draw a circle with pcell rather than polygon points?

Comments

• tomas2004

  September 25

  Hello,

  Here's some Ruby code to insert the "CIRCLE" pcell from the "Basic" Library... It should be easy to convert to Python...

  module MyMacro
  
    include RBA
  
    layout_view = Application.instance.main_window.current_view
  
    layout = layout_view.active_cellview.layout
  
    viewed_cell = layout_view.active_cellview.cell
  
  # Create "CIRCLE" PCell
  #--------------------------
  
          lib = Library.library_by_name("Basic")
  
          lib || raise("Unknown lib 'Basic'")
  
          pcell_decl = lib.layout.pcell_declaration("CIRCLE")
  
          pcell_decl || raise("Unknown PCell 'CIRCLE'")
  
          param = { "layer" => LayerInfo.new(1, 0), "npoints" => 40, "actual_radius" => 5.0 }
  
          pv = pcell_decl.get_parameters.collect do |p|
  
              param[p.name] || p.default
  
          end # collect
  
          pcell_var = layout.add_pcell_variant(lib, pcell_decl.id, pv)
  
          transformation = DTrans.new(DPoint.new(0.0, 30.0))
  
          viewed_cell.insert(DCellInstArray.new(pcell_var, transformation))
  
  end # MyMacro
  

  A pcell has the advantage that it is easier to change afterwards by selecting the pcell instance and changing the properties (PCell parameters)...

  Cheers,

  Tomas
• blueman_44

  September 25

  Adding on to Tomas - here is a link to a ruby pCell circle sample if you want to see the implementation and methods used:
  https://klayout.de/doc/programming/ruby_pcells.html
• Matthias

  September 25 edited September 25

  Very good, thanks for the pointers

  However, I wonder if there is any advantage placing a PCell. A PCell is just a very complicated way to generate layout.

  The easiest way to generate a circle polygon in a Python script is using Polygon#ellipse (https://www.klayout.de/doc-qt5/code/class_Polygon.html#k_42). You give it a box, and this method will create a Polygon object with an ellipse (or circle for a square box) filling the box.

  Matthias
• dick_freebird

  September 26

  There is no such thing as a true circle in a Cartesian
  step-grid system. It's all vectors or pixels and not the
  ideal.

  I always up the vertex-count on drawn circular features
  using the primitive. Kinda fond of 72 as it's got so many
  clean-symmetry divisors.
• Sunfove

  September 29

  Thanks all！ And the code above works.
  I initially wanted to use pcell because the shapes got from polygons showed a difference between the diameters of their incircles and circumcircles. So I thought pcell might be a better way to go. Now I’ve figured out that, for my use case, incircle is correct.
  Pcell is more complicated than I expected, I would keep using polygon method.
• tomas2004

  September 30

  I agree that PCell instantiation in scripts is quite complicated or bulky, especially for ellipses/texts for which dedicated classes/methods are available. However, if you have some (custom made) PCells available you can wrap the code above in a function, and then you need only one line of code in your script to instantiate a PCell, something like:

  def create_pcell_instance(pcellibrary, pcellname, pcellparameters, origin, orientation)
  
     ...
  
  end # def
  

  and in the script:

  create_pcell_instance("basic", "CIRCLE", { "layer" => LayerInfo.new(1, 0), "npoints" => 40, "actual_radius" => 5.0 }, [0.0, 30.0], "R0")

  Cheers,

  Tomas