Class: Mittsu::Triangle

Inherits:
Object
  • Object
show all
Defined in:
lib/mittsu/math/triangle.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(a = Mittsu::Vector3.new, b = Mittsu::Vector3.new, c = Mittsu::Vector3.new) ⇒ Triangle

Returns a new instance of Triangle.



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# File 'lib/mittsu/math/triangle.rb', line 7

def initialize(a = Mittsu::Vector3.new, b = Mittsu::Vector3.new, c = Mittsu::Vector3.new)
  @a, @b, @c = a, b, c
end

Instance Attribute Details

#a ⇒ Object

Returns the value of attribute a.



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# File 'lib/mittsu/math/triangle.rb', line 5

def a
  @a
end

#b ⇒ Object

Returns the value of attribute b.



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# File 'lib/mittsu/math/triangle.rb', line 5

def b
  @b
end

#c ⇒ Object

Returns the value of attribute c.



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# File 'lib/mittsu/math/triangle.rb', line 5

def c
  @c
end

Class Method Details

.barycoord_from_point(point, a, b, c, target = Mittsu::Vector3.new) ⇒ Object

static/instance method to calculate barycoordinates based on: www.blackpawn.com/texts/pointinpoly/default.html



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# File 'lib/mittsu/math/triangle.rb', line 84

def self.barycoord_from_point(point, a, b, c, target = Mittsu::Vector3.new)
  v0 = Mittsu::Vector3.new
  v1 = Mittsu::Vector3.new
  v2 = Mittsu::Vector3.new

  v0.sub_vectors(c, a)
  v1.sub_vectors(b, a)
  v2.sub_vectors(point, a)

  dot00 = v0.dot(v0)
  dot01 = v0.dot(v1)
  dot02 = v0.dot(v2)
  dot11 = v1.dot(v1)
  dot12 = v1.dot(v2)

  denom = dot00 * dot11 - dot01 * dot01

  # colinear or singular triangle
  if denom.zero?
    # arbitrary location outside of triangle?
    # not sure if this is the best idea, maybe should be returning undefined
    return target.set(-2.0, -1.0, -1.0)
  end

  inv_denom = 1.0 / denom
  u = (dot11 * dot02 - dot01 * dot12) * inv_denom
  v = (dot00 * dot12 - dot01 * dot02) * inv_denom

  target.set(1.0 - u - v, v, u)
end

.contains_point?(point, a, b, c) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/mittsu/math/triangle.rb', line 115

def self.contains_point?(point, a, b, c)
  v1 = Mittsu::Vector3.new
  result = Mittsu::Triangle.barycoord_from_point(point, a, b, c, v1)
  result.x >= 0 && result.y >= 0 && result.x + result.y <= 1
end

.normal(a, b, c, target = Mittsu::Vector3.new) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 68

def self.normal(a, b, c, target = Mittsu::Vector3.new)
  v0 = Mittsu::Vector3.new
  target.sub_vectors(c, b)
  v0.sub_vectors(a, b)
  target.cross(v0)

  result_length_sq = target.length_sq
  if (result_length_sq > 0)
    target.multiply_scalar(1.0 / Math.sqrt(result_length_sq))
  else
    target.set(0.0, 0.0, 0.0)
  end
end

Instance Method Details

#area ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 32

def area
  v0 = Mittsu::Vector3.new
  v1 = Mittsu::Vector3.new
  v0.sub_vectors(@c, @b)
  v1.sub_vectors(@a, @b)
  v0.cross(v1).length * 0.5
end

#barycoord_from_point(point, target = Mittsu::Vector3.new) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 52

def barycoord_from_point(point, target = Mittsu::Vector3.new)
  Mittsu::Triangle.barycoord_from_point(point, @a, @b, @c, target)
end

#clone ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 64

def clone
  Mittsu::Triangle.new.copy(self)
end

#contains_point?(point) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/mittsu/math/triangle.rb', line 56

def contains_point?(point)
  Mittsu::Triangle.contains_point?(point, @a, @b, @c)
end

#copy(triangle) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 25

def copy(triangle)
  @a.copy(triangle.a)
  @b.copy(triangle.b)
  @c.copy(triangle.c)
  self
end

#equals(triangle) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 60

def equals(triangle)
  triangle.a.equals(@a) && triangle.b.equals(@b) && triangle.c.equals(@c)
end

#midpoint(target = Mittsu::Vector3.new) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 40

def midpoint(target = Mittsu::Vector3.new)
  target.add_vectors(@a, @b).add(@c).multiply_scalar(1.0 / 3.0)
end

#normal(target = Mittsu::Vector3.new) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 44

def normal(target = Mittsu::Vector3.new)
  Mittsu::Triangle.normal(@a, @b, @c, target)
end

#plane(target = Mittsu::Plane.new) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 48

def plane(target = Mittsu::Plane.new)
  target.set_from_coplanar_points(@a, @b, @c)
end

#set(a, b, c) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 11

def set(a, b, c)
  @a.copy(a)
  @b.copy(b)
  @c.copy(c)
  self
end

#set_from_points_and_indices(points, i0, i1, i2) ⇒ Object 



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# File 'lib/mittsu/math/triangle.rb', line 18

def set_from_points_and_indices(points, i0, i1, i2)
  @a.copy(points[i0])
  @b.copy(points[i1])
  @c.copy(points[i2])
  self
end