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# triangle.rb
module Ruby2D
class Triangle
include Renderable
attr_reader :color
attr_accessor :x1, :y1, :c1,
:x2, :y2, :c2,
:x3, :y3, :c3
def initialize(opts= {})
@x1 = opts[:x1] || 50
@y1 = opts[:y1] || 0
@x2 = opts[:x2] || 100
@y2 = opts[:y2] || 100
@x3 = opts[:x3] || 0
@y3 = opts[:y3] || 100
@z = opts[:z] || 0
self.color = opts[:color] || 'white'
add
end
def color=(c)
@color = Color.from(c)
update_color(@color)
end
# Point is inside a triangle if
# the area of 3 triangles, constructed from triangle sides and that point
# is equal to the area of triangle.
def contains?(x, y)
self_area = triangle_area(@x1, @y1, @x2, @y2, @x3, @y3)
questioned_area =
triangle_area(@x1, @y1, @x2, @y2, x, y) +
triangle_area(@x2, @y2, @x3, @y3, x, y) +
triangle_area(@x3, @y3, @x1, @y1, x, y)
questioned_area <= self_area
end
private
def triangle_area(x1, y1, x2, y2, x3, y3)
(x1*y2 + x2*y3 + x3*y1 - x3*y2 - x1*y3 - x2*y1).abs / 2
end
def update_color(c)
if c.is_a? Color::Set
if c.length == 3
@c1 = c[0]
@c2 = c[1]
@c3 = c[2]
else
raise ArgumentError, "Triangles require 3 colors, one for each vertex. #{c.length} were given."
end
else
@c1 = c
@c2 = c
@c3 = c
end
end
end
end
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