Class: Geom::Polygon

Inherits:
TriangleMesh show all
Defined in:
lib/geom/polygon.rb

Constant Summary collapse

WINDING_CW = 
0
WINDING_CCW = 
1
AXIS_X = 
1
AXIS_Y = 
2
AXIS_Z = 
3
CAP_TOP = 
4
CAP_BASE = 
5
CAP_BOTH = 
6

Instance Attribute Summary

Attributes inherited from TriangleMesh

#data, #faces, #meshes, #tess, #texcoord, #vertices

Instance Method Summary collapse

Methods inherited from TriangleMesh

#<<, #bounding_box, #initialize, #merge, #reverse, #transform_vertices

Constructor Details

This class inherits a constructor from Geom::TriangleMesh

Instance Method Details

#area ⇒ Object 



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# File 'lib/geom/polygon.rb', line 65

def area
  # remove duplicates and invisibles
  return nil if @vertices.length < 3
  @vertices.each{|v| return 0 if @vertices.grep(v).length>1}

  result = 0
  points = @vertices.dup
  plane  = self.plane

  ax = plane.normal.x > 0 ? plane.normal.x : -plane.normal.x
  ay = plane.normal.y > 0 ? plane.normal.y : -plane.normal.y
  az = plane.normal.z > 0 ? plane.normal.z : -plane.normal.z

  coord = AXIS_Z

  if ax > ay
    if ax > az
      coord = AXIS_X
    end
  elsif ay > az
    coord = AXIS_Y
  end

  points.push(points[0],points[1])

  # compute area of the 2D projection
  points.each_with_index do |point,i|
    next if i.zero?
    j = (i+1) % points.length
    k = (i-1) % points.length

    case coord
    when AXIS_X
      result += (point.y * (points[j].z - points[k].z))
    when AXIS_Y
      result += (point.x * (points[j].z - points[k].z))
    else
      result += (point.x * (points[j].y - points[k].y))
    end
  end

  # scale to get area before projection
  an = Math.sqrt(ax**2 + ay**2 + az**2) # length of normal vector
  case coord
  when AXIS_X
    result *= (an / (2*ax))
  when AXIS_Y
    result *= (an / (2*ay))
  when AXIS_Z
    result *= (an / (2*az))
  end
  2.times {points.pop}
  result
end

#calc_uv ⇒ Object 



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# File 'lib/geom/polygon.rb', line 206

def calc_uv
  result = []
  plane = self.plane
  up = Number3D.new( 0, 1, 0 )

  # get side vector
  side = Number3D.cross(up, plane.normal)
  side.normalize

  # adjust up vector
  up = Number3D.cross(self.plane.normal, side)
  up.normalize

  matrix  = Matrix3D[
          [side.x, up.x, plane.normal.x, 0],
          [side.y, up.y, plane.normal.y, 0],
          [side.z, up.z, plane.normal.z, 0],
          [0, 0, 0, 1]]

  v, n, t = nil, nil, nil
  min = Number3D.new(1000,1000,1000)
  max = Number3D.new(-min.x, -min.y, -min.z)
  pts = []

  @vertices.each do |v|
    n = v.position

    # Matrix3D.multiplyVector3x3( matrix, n );

    min.x = n.x if n.x < min.x
    min.y = n.y if n.y < min.y
    max.x = n.x if n.x > max.x
    max.y = n.y if n.y > max.y

    pts << n
    result << NumberUV.new
  end

  w = max.x - min.x
  h = max.y - min.y
  size = w < h ? h : w

  @vertices.each_with_index do |v,i|
    n = pts[i]
    t = result[i]

    t.u = ((n.x - min.x) / size) * size
    t.v = ((n.y - min.y) / size) * size
  end

  result
end

#clone ⇒ Object 



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# File 'lib/geom/polygon.rb', line 15

def clone
  vertices = @vertices.collect{|v| v.clone}
  texcoord = @texcoord ? @texcoord.collect{|uv| uv.clone} : nil
  faces    = @faces.collect do |f|
    if texcoord
      Triangle.new([
        vertices[ @vertices.index(f.vertices[0]) ],
        vertices[ @vertices.index(f.vertices[1]) ],
        vertices[ @vertices.index(f.vertices[2]) ]
      ],[
        texcoord[ @texcoord.index(f.texcoord[0]) ],
        texcoord[ @texcoord.index(f.texcoord[1]) ],
        texcoord[ @texcoord.index(f.texcoord[2]) ]
      ])
    else
      Triangle.new([
        vertices[ @vertices.index(f.vertices[0]) ],
        vertices[ @vertices.index(f.vertices[1]) ],
        vertices[ @vertices.index(f.vertices[2]) ]
      ])
    end
  end
  result = Polygon.new(vertices,faces,@data.dup)
  result.texcoord = texcoord
  result
end

#dominant_axis ⇒ Object 



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# File 'lib/geom/polygon.rb', line 187

def dominant_axis
  plane = self.plane
  return 0 unless plane

  ax = (plane.normal.x > 0 ? plane.normal.x : -plane.normal.x)
  ay = (plane.normal.y > 0 ? plane.normal.y : -plane.normal.y)
  az = (plane.normal.z > 0 ? plane.normal.z : -plane.normal.z)

  axis = AXIS_Z
  if ax > ay
    if ax > az
      axis = AXIS_X
    end
  elsif ay > az
    axis = AXIS_Y
  end
  axis
end

#extrude(distance, direction, cap = CAP_BOTH, update = true) ⇒ Object 



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# File 'lib/geom/polygon.rb', line 153

def extrude(distance,direction,cap=CAP_BOTH,update=true)
  direction.normalize
  top_cap = clone
  top_cap.vertices.each do |v|
    v.x += distance*direction.x
    v.y += distance*direction.y
    v.z += distance*direction.z
  end
  top_cap.faces.each {|f| f.normal = direction }
  num = @vertices.length

  sides = Array.new(@vertices.length).map!{ Polygon.new }
  sides.each_with_index do |side,i|
    j = (i+1) % num
    side.vertices.push(top_cap.vertices[i],top_cap.vertices[j])
    side.vertices.push(@vertices[j],@vertices[i])
    side.data[:side] = true
    side.update if update
  end

  case cap
  when CAP_BASE
    top_cap.faces.clear
  when CAP_TOP
    self.faces.clear
  when CAP_BOTH
    self.faces.each do |f|
      f.flip_normal
    end
  end

  sides + [top_cap]
end

#plane ⇒ Object

TODO real plane, not just from first 3 vertices



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# File 'lib/geom/polygon.rb', line 121

def plane
  return nil if @vertices.length < 3
  Plane.three_points(*@vertices[0..2])
end

#point_inside(pt) ⇒ Object 



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# File 'lib/geom/polygon.rb', line 126

def point_inside(pt)
  x = pt.x;
  y = pt.y;
  c = false;
  length = @vertices.length
  
  length.times do |i|
    j = (i+1) % length

    a = @vertices[i]
    b = @vertices[j]

    xpi = a.x
    ypi = a.y
    xpj = b.x
    ypj = b.y
    if ((((ypi<=y) && (y<ypj)) || ((ypj<=y) && (y<ypi))) && (x < (xpj-xpi)*(y-ypi)/(ypj-ypi)+xpi))
      c = !c
    end
  end
  return c;      
end

#update ⇒ Object 



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# File 'lib/geom/polygon.rb', line 42

def update
  return false if @vertices.length < 3
  triangles = @tess.triangulate(self)
  unless triangles
    @vertices.reverse!
    triangles = @tess.triangulate(self)
    return false unless triangles
  end

  @texcoord = calc_uv
  triangles.each do |t|
    v0 = @vertices[t[0]]
    v1 = @vertices[t[1]]
    v2 = @vertices[t[2]]

    t0 = @texcoord[t[0]]
    t1 = @texcoord[t[1]]
    t2 = @texcoord[t[2]]
    @faces.push(Triangle.new([v2,v1,v0],[t0,t1,t2]))
  end
  true
end

#winding ⇒ Object 



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# File 'lib/geom/polygon.rb', line 149

def winding
  area < 0 ? WINDING_CW : WINDING_CCW
end