Module: Polygon

Included in:
Curses::Geometry
Defined in:
lib/curses/geometry/polygon.rb

Instance Method Summary collapse

Instance Method Details

#fill_polygon(vertices) ⇒ Object 



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# File 'lib/curses/geometry/polygon.rb', line 55

def fill_polygon (vertices)

  # Clearing the rasterizer's buffers :
  @left_scan   = Array.new(lines) { 1000000 }
  @right_scan  = Array.new(lines) {       0 }

  # Finding the top and bottom of the polygon :

  # Initializing the loop with the first point y value :
  max_y_index = 0
  min_y_index = 0

  max_y = vertices[max_y_index][1].to_i
  min_y = vertices[min_y_index][1].to_i

  vertices.each.with_index do |vertex,i|
    # Find the bottom index :
    if (vertex[1] < min_y) then
      min_y       = vertex[1].to_i
      min_y_index = i
    end

    # Find the top index :
    if vertex[1] > max_y then
      max_y       = vertex[1].to_i
      max_y_index = i
    end
  end


  # Discard null height polygons :
  return if min_y == max_y


  # Devise the winding order :
  previous_point_x  = vertices[(max_y_index - 1 + vertices.length) % vertices.length][0].to_i
  next_point_x      = vertices[(max_y_index + 1) % vertices.length][0].to_i
  winding_order     = previous_point_x < next_point_x ? -1 : 1


  # Scan the left and right edges of the polygon :

  # Left :
  i = 0
  while( vertices[( ( max_y_index + i * winding_order ) + vertices.length) % vertices.length][1] != min_y ) do
    index       = ( ( max_y_index + i * winding_order ) + vertices.length ) % vertices.length
    next_index  = ( ( max_y_index + ( i + 1 ) * winding_order ) + vertices.length ) % vertices.length
    scan_polygon_left_edge( vertices[index][0],
                            vertices[index][1],
                            vertices[next_index][0],
                            vertices[next_index][1] )

    i += 1
  end
  
  # Right :
  i = 0;
  while ( vertices[( ( max_y_index - i * winding_order ) + vertices.length ) % vertices.length][1] != min_y ) do
    index       = ( ( max_y_index - i * winding_order ) + vertices.length ) % vertices.length
    next_index  = ( ( max_y_index - ( i + 1 ) * winding_order ) + vertices.length ) % vertices.length
    scan_polygon_right_edge(  vertices[index][0],
                              vertices[index][1],
                              vertices[next_index][0],
                              vertices[next_index][1] )

    i += 1
  end


  # Draw the polygon :
  min_y.upto(max_y) do |y|
    @left_scan[y].upto(@right_scan[y]) do |x|
      setpos(y, x)
      addch(get_fill_glyph)
    end
  end

end

#scan_polygon_left_edge(x1, y1, x2, y2) ⇒ Object

Methods :



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# File 'lib/curses/geometry/polygon.rb', line 8

def scan_polygon_left_edge(x1, y1, x2, y2)

  # Escape horizontal lines :
  return if (y1 - y2).abs < 0.75 


  # Calculating useful values for the scanning loop :
  islope    = ( x2 - x1 ).to_f / ( y2 - y1 ).to_f
  #islope    = ( x2 - x1 ) / ( y2 - y1 )

  y_top     = y1 > 0.5 ? ( y1 - 0.5 ).floor.to_i : 0.0
  y_bottom  = ( y2 + 0.5 ).floor.to_i

  x         = ( y_top + 0.5 - y1 ) * islope + x1      # + 0.5 : the scan line goes through the middle of the pixel


  # Scan converting :
  y_top.downto(y_bottom) do |y|
    @left_scan[y] = ( x + 0.5 ).floor.to_i
    x -= islope
  end
end

#scan_polygon_right_edge(x1, y1, x2, y2) ⇒ Object 



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# File 'lib/curses/geometry/polygon.rb', line 32

def scan_polygon_right_edge(x1, y1, x2, y2)

  # Escape horizontal lines :
  return if ( y1 - y2 ).abs <  0.75

  # Calculating useful values for the scanning loop :
  islope    = ( x2 - x1 ).to_f / ( y2 - y1 ).to_f
  #islope    = ( x2 - x1 ) / ( y2 - y1 )

  y_top     = y1 > 0.5 ? ( y1 - 0.5 ).floor.to_i : 0.0
  y_bottom  = ( y2 + 0.5 ).floor.to_i

  x         = ( y_top + 0.5 - y1 ) * islope + x1        # + 0.5 : the scan line goes through the middle of the pixel


  # Scan converting :
  y_top.downto(y_bottom) do |y|
    @right_scan[y] = x > 0.5 ? ( x - 0.5 ).floor.to_i : 0.0
    x -= islope
  end
end