#!ruby -Ks
# -*- mode: ruby; coding: sjis -*-
# Last updated: <2016/02/14 03:42:39 +0900>
#
# DXRubyでスプライン曲線を描画
# 2次スプラインなのか、3次スプラインかなのか不明
#
# 参考ページ
#
# Flashゲーム講座＆ASサンプル集【曲線について】
# http://hakuhin.jp/as/curve.html#CURVE_04

require 'dxruby'
require 'pp'

# スプライン補間用クラス
#
# @attr [Array] result スプライン補間した座標群が配列の形で入る
#
class SplineStream

  # x,y座標保持用クラス
  class Vec
    attr_accessor :x
    attr_accessor :y

    def initialize(x, y)
      @x = x.to_f
      @y = y.to_f
    end
  end

  attr_accessor :result

  # コンストラクタ
  # @param [Array] poslist 座標群。一要素が[x,y]になってる配列
  # @param [Number] interpolate 分解度
  def initialize(poslist, interpolate)
    init(poslist, interpolate)
  end

  # 座標群から補間値を生成する
  # @param [Array] poslist 座標群。一要素が[x,y]になってる配列
  # @param [Number] interpolate 分解度
  def init(poslist, interpolate)
    @num = poslist.length
    @l = []
    @aa = []
    @bb = []
    @cc = []

    p = []
    poslist.each do |d|
      p.push(Vec.new(d[0], d[1]))
    end

    0.step(@num - 2, 1) do |i|
      p0 = p[i]
      p1 = p[i+1]
      @l[i] = Math.sqrt((p0.x - p1.x) * (p0.x - p1.x) + (p0.y - p1.y) * (p0.y - p1.y))
    end

    @aa[0] = [0.0, 1.0, 0.5]
    @bb[0] = {
      :x => (3.0 / (2.0 * @l[0])) * (p[1].x - p[0].x),
      :y => (3.0 / (2.0 * @l[0])) * (p[1].y - p[0].y)
    }

    @aa[@num - 1] = [1.0, 2.0, 0.0]
    @bb[@num - 1] = {
      :x => (3.0 / @l[@num - 2]) * (p[@num - 1].x - p[@num - 2].x),
      :y => (3.0 / @l[@num - 2]) * (p[@num - 1].y - p[@num - 2].y)
    }

    1.step(@num - 2, 1) do |i|
      a = @l[i - 1]
      b = @l[i]
      @aa[i] = [b, 2.0 * (b + a), a]
      @bb[i] = {
        :x => (3.0 * (a * a * (p[i + 1].x - p[i].x)) + 3.0 * b * b * (p[i].x - p[i - 1].x)) / (b * a),
        :y => (3.0 * (a * a * (p[i + 1].y - p[i].y)) + 3.0 * b * b * (p[i].y - p[i - 1].y)) / (b * a)
      }
    end

    1.step(@num - 1, 1) do |i|
      d = @aa[i-1][1] / @aa[i][0]
      @aa[i] = [0, @aa[i][1] * d - @aa[i-1][2], @aa[i][2] * d]
      @bb[i][:x] = @bb[i][:x] * d - @bb[i - 1][:x]
      @bb[i][:y] = @bb[i][:y] * d - @bb[i - 1][:y]

      @aa[i][2] /= @aa[i][1]
      @bb[i][:x] /= @aa[i][1]
      @bb[i][:y] /= @aa[i][1]
      @aa[i][1] = 1
    end

    @cc[@num - 1] = {
      :x => @bb[@num-1][:x],
      :y => @bb[@num-1][:y]
    }

    (@num - 1).step(1, -1) do |j|
      @cc[j - 1] = {
        :x => @bb[j - 1][:x] - @aa[j - 1][2] * @cc[j][:x],
        :y => @bb[j - 1][:y] - @aa[j - 1][2] * @cc[j][:y]
      }
    end

    outdata = []
    count = 0
    0.step(@num - 2, 1) do |i|
      a = @l[i]
      v00 = p[i].x
      v01 = @cc[i][:x]
      v02 = (p[i + 1].x - p[i].x) * 3.0 / (a * a) - (@cc[i + 1][:x] + 2 * @cc[i][:x]) / a
      v03 = (p[i + 1].x - p[i].x) * (-2.0 / (a * a * a)) + (@cc[i + 1][:x] + @cc[i][:x]) * (1.0 / (a * a))

      v10 = p[i].y
      v11 = @cc[i][:y]
      v12 = (p[i + 1].y - p[i].y) * 3.0 / (a * a) - (@cc[i + 1][:y] + 2 * @cc[i][:y]) / a
      v13 = (p[i + 1].y - p[i].y) * (-2.0 / (a * a * a)) + (@cc[i + 1][:y] + @cc[i][:y]) * (1.0 / (a * a))

      t = 0.0
      t_spd = a.to_f / interpolate.to_f
      0.step(interpolate - 1, 1) do |j|
        tx = ((v03 * t + v02) * t + v01) * t + v00
        ty = ((v13 * t + v12) * t + v11) * t + v10
        outdata.push([tx, ty])
        t += t_spd
      end
    end

    outdata.push([p[@num-1].x, p[@num-1].y])

    @result = outdata
  end
end

if $0 == __FILE__
  # ----------------------------------------
  # 動作確認

  Window.caption = "Spline Curve"

  # 四角(塗り潰し)を描画
  def draw_dot(x, y, sz, col)
    sz = sz / 2.0
    Window.drawBoxFill(x - sz, y - sz, x + sz, y + sz, col)
  end

  # 点を描画
  def draw_dot2(x, y, col)
    Window.drawLine(x, y, x, y, col)
  end

  # 四角(線のみ)を描画
  def draw_box(x, y, sz, col)
    sz = sz / 2.0
    x1, y1 = x - sz, y - sz
    x2, y2 = x + sz, y + sz
    Window.drawLine(x1, y1, x2, y1, col)
    Window.drawLine(x1, y2, x2, y2, col)
    Window.drawLine(x1, y1, x1, y2, col)
    Window.drawLine(x2, y1, x2, y2, col)
  end

  fnt = Font.new(12)

  # 1区間を何分割するか
  interpolate = 16

  # 初期座標群
  poslist = [
    [50, 200],
    [150, 200],
    [250, 100],
    [350, 400],
    [450, 200],
    [550, 100],
  ]

  spline = SplineStream.new(poslist, interpolate)
  mode = 0

  Window.loop do
    break if Input.keyPush?(K_ESCAPE)

    if Input.mousePush?(M_LBUTTON)
      # マウスボタンがクリックされたら座標変更
      poslist[mode] = [Input.mousePosX.to_f, Input.mousePosY.to_f]
      mode += 1
      mode = 0 if mode >= poslist.length

      # スプライン曲線を作り直し
      spline.init(poslist, interpolate)
    end

    # 制御点を描画
    poslist.each_with_index do |d, i|
      x, y = d
      draw_dot(x, y, 6, C_RED)
      draw_box(x, y, 12, C_CYAN) if i == mode
    end

    # スプライン曲線を描画
    spline.result.each do |d|
      x, y = d
      draw_dot2(x, y, C_WHITE)
    end

    Window.drawFont(4, 4, "Please Click", fnt)
  end
end