Random MACL trouble; draw_polygon

[BwdYeti]

[rgss]  #-------------------------------------------------------------------------
  # * Name      : Draw Polygon
  #   Info      : Draws a Polygon
  #   Author    : Caesar (Rewrote By Trickster)
  #   Call Info : Array vertices - Points of the polygon
  #               Integer width - Thickness of the lines
  #               Color color - color to draw it in
  #               Boolean filled - false outline true filled
  #               Integer step - fill steps
  #   Comments  : Example of vertices setup [[30, 80], [80, 80], [30, 60]]
  #-------------------------------------------------------------------------
  def draw_polygon(vertices, stroke = 1, color = Color.new(255, 255, 255),
    filled = false, step = 1)
    # Return if no width or not enough points
    return if stroke <= 0 or vertices.size <= 2
    # Get Count
    count = vertices.size
    # Get Points
    x1, y1, x2, y2 = vertices[-1] + vertices[0]
    # Draw Line
    draw_line(x1, y1, x2, y2, stroke, color)
    # Shade if filled
    shade_section(cx, cy, x1, y1, x2, y2, stroke, step, color) if filled
    # Run Through with next
    vertices.each_with_next do |start, point|
      # Get Points
      x1, y1, x2, y2 = start + point
      # Draw Line
      draw_line(x1, y1, x2, y2, stroke, color)
      # Shade if filled
      shade_section(cx, cy, x1, y1, x2, y2, stroke, step, color) if filled
    end
  end
  #-------------------------------------------------------------------------
  # * Name      : Shade Section
  #   Info      : Shades a section from (cx,cy), (x1,y1), (x2,y2)
  #   Author    : Trickster
  #   Call Info : Six to Nine Arguments
  #               Integer cx, cy, x1, y1, x2, y2 - Points
  #               Integer Thick - Line Thickness
  #               Integer Step - how many lines to draw (lower = higher accuracy)
  #               Color color - color to shade in
  #-------------------------------------------------------------------------
  def shade_section(cx, cy, x1, y1, x2, y2, thick = 1, step = 1,
      color = Color.new(255, 255, 255))
    # Reverse all parameters sent if 2 x is less than the first x
    x1, x2, y1, y2 = x2, x1, y2, y1 if x2 < x1    
    # Get Slope
    slope = (y2 - y1).to_f / (x2 - x1)
    # If Slope is infinite
    if slope.infinite?
      y1.step(y2, step) {|y| draw_line(cx, cy, x1, y, thick, color)}
    # If Slope is zero
    elsif slope.zero?
      x1.step(x2, step) {|x| draw_line(cx, cy, x, y1, thick, color)}
    elsif not slope.nan?
      # Get Y intercept
      yint = y1 - slope * x1
      x1.step(x2, step) {|x| draw_line(cx, cy, x, slope * x + yint, thick, color)}
    end
  end
[/rgss]

cx and cy are undefined, so it doesn't work. Does anyone know how it should figure them out? (Or what they're even for?)

 

[Brewmeister]

It looks like the "shade_section" method fills in a triangle (3 points), so if cx & cy are set to any point on the polygon, it should work. Try setting them to the first point. Right above the first "shade_section" insert

cx, cy = x1, y1

 

[BwdYeti]

Ah, that helps some. It's kinda working now. But that made some weird banding in half of it. So I think what it wants to do is make triangles from each set of three points in a row (0,1,2; 1,2,3; 2,3,4; etc), I edited it to do that and it seems to work.
[rgss]  def draw_polygon(vertices, stroke = 1, color = Color.new(255, 255, 255),
    filled = false, step = 1)
    # Return if no width or not enough points
    return if stroke <= 0 or vertices.size <= 2
    # Get Count
    count = vertices.size
    # Run Through
    for i in 0...count
      # Get Points
      x1, y1, x2, y2 = vertices[i - 0] + vertices[i - 1]
      # Draw Line
      draw_line(x1, y1, x2, y2, stroke, color)
      # Shade if filled
      if filled
        cx, cy = vertices[i - 2]
        shade_section(cx, cy, x1, y1, x2, y2, stroke, step, color)
      end
    end
  end
[/rgss]
Changed the "do |things|" iteration to a for loop because I have no idea how those work :/

 

[Brewmeister]

If you call this with a polygon of more than 4 sides, it will leave a hole in the middle.

 

[BwdYeti]

fgsfds, you're right. I guess your way has to do.

EDIT

So to deal with the lines like that I increase the step?

 

[Brewmeister]

I would say decrease the step, but the default of 1 should theoretically fill it in.

 

[BwdYeti]

Er, yeah decrease the number, increase the amount of lines it draws.
Even with a step of .5 it didn't fill a larger octagon in fully, so I'll probably just use images instead of drawing it in realtime, since it's a bit slow.