From fcbf63e62c627deae76c1b8cb8c0876c536ed811 Mon Sep 17 00:00:00 2001 From: Jari Vetoniemi Date: Mon, 16 Mar 2020 18:49:26 +0900 Subject: Fresh start --- jni/ruby/ext/tk/sample/demos-en/pendulum.rb | 240 ++++++++++++++++++++++++++++ 1 file changed, 240 insertions(+) create mode 100644 jni/ruby/ext/tk/sample/demos-en/pendulum.rb (limited to 'jni/ruby/ext/tk/sample/demos-en/pendulum.rb') diff --git a/jni/ruby/ext/tk/sample/demos-en/pendulum.rb b/jni/ruby/ext/tk/sample/demos-en/pendulum.rb new file mode 100644 index 0000000..306ac94 --- /dev/null +++ b/jni/ruby/ext/tk/sample/demos-en/pendulum.rb @@ -0,0 +1,240 @@ +# +# This demonstration illustrates how Tcl/Tk can be used to construct +# simulations of physical systems. +# (called by 'widget') +# +# based on Tcl/Tk8.5a2 widget demos + +# destroy toplevel widget for this demo script +if defined?($pendulum_demo) && $pendulum_demo + $pendulum_demo.destroy + $pendulum_demo = nil +end + +# create toplevel widget +$pendulum_demo = TkToplevel.new {|w| + title("Pendulum Animation Demonstration") + iconname("pendulum") + positionWindow(w) +} + +base_frame = TkFrame.new($pendulum_demo).pack(:fill=>:both, :expand=>true) + +# create label +msg = TkLabel.new(base_frame) { + font $font + wraplength '4i' + justify 'left' + text 'This demonstration shows how Ruby/Tk can be used to carry out animations that are linked to simulations of physical systems. In the left canvas is a graphical representation of the physical system itself, a simple pendulum, and in the right canvas is a graph of the phase space of the system, which is a plot of the angle (relative to the vertical) against the angular velocity. The pendulum bob may be repositioned by clicking and dragging anywhere on the left canvas.' +} +msg.pack('side'=>'top') + +# create frame +TkFrame.new(base_frame) {|frame| + TkButton.new(frame) { + text 'Dismiss' + command proc{ + tmppath = $pendulum_demo + $pendulum_demo = nil + tmppath.destroy + } + }.pack('side'=>'left', 'expand'=>'yes') + + TkButton.new(frame) { + text 'See Code' + command proc{showCode 'pendulum'} + }.pack('side'=>'left', 'expand'=>'yes') + +}.pack('side'=>'bottom', 'fill'=>'x', 'pady'=>'2m') + +# animated wave +class PendulumAnimationDemo + def initialize(frame) + # Create some structural widgets + @pane = TkPanedWindow.new(frame, :orient=>:horizontal).pack(:fill=>:both, :expand=>true) +# @pane.add(@lf1 = TkLabelFrame.new(@pane, :text=>'Pendulum Simulation')) +# @pane.add(@lf2 = TkLabelFrame.new(@pane, :text=>'Phase Space')) + @lf1 = TkLabelFrame.new(@pane, :text=>'Pendulum Simulation') + @lf2 = TkLabelFrame.new(@pane, :text=>'Phase Space') + + # Create the canvas containing the graphical representation of the + # simulated system. + @c = TkCanvas.new(@lf1, :width=>320, :height=>200, :background=>'white', + :borderwidth=>2, :relief=>:sunken) + TkcText.new(@c, 5, 5, :anchor=>:nw, + :text=>'Click to Adjust Bob Start Position') + # Coordinates of these items don't matter; they will be set properly below + @plate = TkcLine.new(@c, 0, 25, 320, 25, :width=>2, :fill=>'grey50') + @rod = TkcLine.new(@c, 1, 1, 1, 1, :width=>3, :fill=>'black') + @bob = TkcOval.new(@c, 1, 1, 2, 2, + :width=>3, :fill=>'yellow', :outline=>'black') + TkcOval.new(@c, 155, 20, 165, 30, :fill=>'grey50', :outline=>'') + + # pack + @c.pack(:fill=>:both, :expand=>true) + + # Create the canvas containing the phase space graph; this consists of + # a line that gets gradually paler as it ages, which is an extremely + # effective visual trick. + @k = TkCanvas.new(@lf2, :width=>320, :height=>200, :background=>'white', + :borderwidth=>2, :relief=>:sunken) + @y_axis = TkcLine.new(@k, 160, 200, 160, 0, :fill=>'grey75', :arrow=>:last) + @x_axis = TkcLine.new(@k, 0, 100, 320, 100, :fill=>'grey75', :arrow=>:last) + + @graph = {} + 90.step(0, -10){|i| + # Coordinates of these items don't matter; + # they will be set properly below + @graph[i] = TkcLine.new(@k, 0, 0, 1, 1, :smooth=>true, :fill=>"grey#{i}") + } + + # labels + @label_theta = TkcText.new(@k, 0, 0, :anchor=>:ne, + :text=>'q', :font=>'Symbol 8') + @label_dtheta = TkcText.new(@k, 0, 0, :anchor=>:ne, + :text=>'dq', :font=>'Symbol 8') + + # pack + @k.pack(:fill=>:both, :expand=>true) + + # Initialize some variables + @points = [] + @theta = 45.0 + @dTheta = 0.0 + @length = 150 + + # animation loop + @timer = TkTimer.new(15){ repeat } + + # binding + @c.bindtags_unshift(btag = TkBindTag.new) + btag.bind('Destroy'){ @timer.stop } + btag.bind('1', proc{|x, y| @timer.stop; showPendulum(x.to_i, y.to_i)}, + '%x %y') + btag.bind('B1-Motion', proc{|x, y| showPendulum(x.to_i, y.to_i)}, '%x %y') + btag.bind('ButtonRelease-1', + proc{|x, y| showPendulum(x.to_i, y.to_i); @timer.start }, + '%x %y') + + btag.bind('Configure', proc{|w| @plate.coords(0, 25, w.to_i, 25)}, '%w') + + @k.bind('Configure', proc{|h, w| + h = h.to_i + w = w.to_i + @psh = h/2; + @psw = w/2 + @x_axis.coords(2, @psh, w-2, @psh) + @y_axis.coords(@psw, h-2, @psw, 2) + @label_theta.coords(@psw-4, 6) + @label_dtheta.coords(w-6, @psh+4) + }, '%h %w') + + # add + Tk.update + @pane.add(@lf1) + @pane.add(@lf2) + + # init display + showPendulum + + # animation start + @timer.start(500) + end + + # This procedure makes the pendulum appear at the correct place on the + # canvas. If the additional arguments x, y are passed instead of computing + # the position of the pendulum from the length of the pendulum rod and its + # angle, the length and angle are computed in reverse from the given + # location (which is taken to be the centre of the pendulum bob.) + def showPendulum(x=nil, y=nil) + if x && y && (x != 160 || y != 25) + @dTheta = 0.0 + x2 = x - 160 + y2 = y - 25 + @length = Math.hypot(x2, y2) + @theta = Math.atan2(x2,y2)*180/Math::PI + else + angle = @theta*Math::PI/180 + x = 160 + @length*Math.sin(angle) + y = 25 + @length*Math.cos(angle) + end + + @rod.coords(160, 25, x, y) + @bob.coords(x-15, y-15, x+15, y+15) + end + + # Update the phase-space graph according to the current angle and the + # rate at which the angle is changing (the first derivative with + # respect to time.) + def showPhase + unless @psw && @psh + @psw = @k.width/2 + @psh = @k.height/2 + end + @points << @theta + @psw << -20*@dTheta + @psh + if @points.length > 100 + @points = @points[-100..-1] + end + (0...100).step(10){|i| + first = - i + last = 11 - i + last = -1 if last >= 0 + next if first > last + lst = @points[first..last] + @graph[i].coords(lst) if lst && lst.length >= 4 + } + end + + # This procedure is the "business" part of the simulation that does + # simple numerical integration of the formula for a simple rotational + # pendulum. + def recomputeAngle + scaling = 3000.0/@length/@length + + # To estimate the integration accurately, we really need to + # compute the end-point of our time-step. But to do *that*, we + # need to estimate the integration accurately! So we try this + # technique, which is inaccurate, but better than doing it in a + # single step. What we really want is bound up in the + # differential equation: + # .. - sin theta + # theta + theta = ----------- + # length + # But my math skills are not good enough to solve this! + + # first estimate + firstDDTheta = -Math.sin(@theta * Math::PI/180) * scaling + midDTheta = @dTheta + firstDDTheta + midTheta = @theta + (@dTheta + midDTheta)/2 + # second estimate + midDDTheta = -Math.sin(midTheta * Math::PI/180) * scaling + midDTheta = @dTheta + (firstDDTheta + midDDTheta)/2 + midTheta = @theta + (@dTheta + midDTheta)/2 + # Now we do a double-estimate approach for getting the final value + # first estimate + midDDTheta = -Math.sin(midTheta * Math::PI/180) * scaling + lastDTheta = midDTheta + midDDTheta + lastTheta = midTheta + (midDTheta+ lastDTheta)/2 + # second estimate + lastDDTheta = -Math.sin(lastTheta * Math::PI/180) * scaling + lastDTheta = midDTheta + (midDDTheta + lastDDTheta)/2 + lastTheta = midTheta + (midDTheta + lastDTheta)/2 + # Now put the values back in our globals + @dTheta = lastDTheta + @theta = lastTheta + end + + # This method ties together the simulation engine and the graphical + # display code that visualizes it. + def repeat + # Simulate + recomputeAngle + + # Update the display + showPendulum + showPhase + end +end + +# Start the animation processing +PendulumAnimationDemo.new(base_frame) -- cgit v1.2.3