#!ruby -Ks
# -*- mode: ruby; coding: sjis -*-
# Last updated: <2016/02/13 03:59:49 +0900>
#
# DXRubyでCatmull-Romスプライン曲線を描画してみる
#
# Catmull-Rom 補間 - blog.seyself.com
# http://blog.seyself.com/2008/06/post_2008061020.html
#
# デジタル・フロンティア-Digital Frontier | DF TALK | スプライン曲線の話
# http://www.dfx.co.jp/dftalk/?p=10576

require 'dxruby'

Window.caption = "Catmul-Rom Spline Curve"

# Catmul-Rom補間の値を取得
#
# @param p0 [Number] 値0
# @param p1 [Number] 値1
# @param p2 [Number] 値2
# @param p3 [Number] 値3
# @param t [Number] t値 (0.0 - 1.0)
# @return [Number] 結果 (p1 - p2 の間で値を返す)
def get_catmul_rom(p0, p1, p2, p3, t)
  t = t.to_f
  v0 = (p2 - p0).to_f * 0.5
  v1 = (p3 - p1).to_f * 0.5
  t2 = t * t
  t3 = t2 * t
  return ((p1 - p2) * 2 + v0 + v1) * t3 + \
  ((p2 - p1) * 3 - 2 * v0 - v1) * t2 + v0 * t + p1
end

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

# 四角(線)を描画
def draw_box(x, y, sz, color)
  x1, y1 = x - sz, y - sz
  x2, y2 = x + sz, y + sz
  Window.drawLine(x1, y1, x2, y1, color)
  Window.drawLine(x2, y1, x2, y2, color)
  Window.drawLine(x1, y1, x1, y2, color)
  Window.drawLine(x1, y2, x2, y2, color)
end

fnt = Font.new(12)

# 制御点を初期化
x = 16
y = 64
dx = 120
dy = 40
p = []
8.times do |i|
  p.push([x, y])
  x += dx
  y += dy
end

mode = 0

Window.resize(1024, 768)

# メインループ
Window.loop do
  break if Input.keyPush?(K_ESCAPE)

  if Input.mousePush?(M_LBUTTON)
    # マウスボタンが押されたので制御点の座標を変更
    p[mode] = [Input.mousePosX.to_f, Input.mousePosY.to_f]
    mode += 1
    mode = 0 if mode >= p.length
  end

  # 制御点を描画
  p.each_with_index do |c, i|
    x, y = c
    draw_dot(x, y, 3, C_RED)
    draw_box(x, y, 6, C_CYAN) if i == mode
  end

  # Catmul-Rom Spline を描画
  (p.length - 3).times do |i|
    n0, n1, n2, n3 = i, i+1, i+2, i+3
    x0, x1, x2, x3 = p[n0][0], p[n1][0], p[n2][0], p[n3][0]
    y0, y1, y2, y3 = p[n0][1], p[n1][1], p[n2][1], p[n3][1]

    0.step(1.0 - 0.05, 0.05) do |t|
      x = get_catmul_rom(x0, x1, x2, x3, t)
      y = get_catmul_rom(y0, y1, y2, y3, t)
      draw_dot(x, y, 1, C_WHITE)
    end
  end

  Window.drawFont(4, 4, "Please click [#{mode}]", fnt)
end