Class: XRVG::SimpleBezier

Inherits:
BezierBuilder show all
Defined in:
lib/beziertools.rb

Overview

FittingBezier is a better class for point bezier interpolation. However, this class is kept mainly for historical reasons.

Instance Method Summary collapse

Methods inherited from BezierBuilder

[], build, lissage

Instance Method Details

#compute ⇒ Object

BezierBuilder overloading: see SimpleBezier description for algorithm



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# File 'lib/beziertools.rb', line 24

def compute( )
  points = @support
  if points.length < 2
    Kernel::raise("SimpleBezier support must have at least two points")
  elsif points.length == 2
    return LinearBezier.build( :support, points).data
  end
  
  result = Array.new
  p1      = points[0]
  v1      = V2D::O
  cpiece = [:vector, p1, v1]
  
  points.triplets do |p1, p2, p3|
    v = ((p2 - p1)..( p3 - p2 )).middle * 1.0 / 3.0
    result.push( cpiece + [p2, v.reverse] )
    cpiece = [:vector, p2, v]
  end

  pr2 = points[-1]
  vr2 = V2D::O
  result.push( cpiece + [pr2, vr2] )

  # compute first and last piece again, by symetry
  piece0 = Bezier.single( *result[0] )
  p1, v1, p2, v2 = piece0.pointlist(:vector)
  pv     = (p2 - p1)
  angle  = v2.angle - pv.angle 
  v1     = (-v2).rotate( -2.0 * angle )
  result[0] = [:vector, p1, v1, p2, v2]

  piecel = Bezier.single( *result[-1] )
  p1, v1, p2, v2 = piecel.pointlist(:vector)
  pv     = (p2 - p1)
  angle  = v1.angle - pv.angle 
  v2     = (-v1).rotate(  -2.0 * angle )
  result[-1] = [:vector, p1, v1, p2, v2]

  return result
end