113 lines
3.1 KiB
Nim
113 lines
3.1 KiB
Nim
# Pendulum simulation.
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import math, random
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import gintro/[gobject, gdk, gtk, gio, glib, cairo]
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const
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Width = 500
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Height = 500
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DrawIters = 72
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Red = [float 1, 0, 0]
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Green = [float 0, 1, 0]
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Blue = [float 0, 0, 1]
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Black = [float 0, 0, 0]
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White = [float 255, 255, 255]
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Gold = [float 255, 215, 0]
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Colors = [Blue, Red, Green, White, Gold]
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Angles = [75, 100, 135, 160]
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type
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Vec2 = tuple[x, y: float]
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Point = Vec2
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# Description of the simulation.
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Simulation = ref object
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area: DrawingArea
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xmax, ymax: float
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center: Point
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itercount: int
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#---------------------------------------------------------------------------------------------------
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proc newSimulation(area: DrawingArea; width, height: int): Simulation {.noInit.} =
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## Allocate and initialize the simulation object.
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new(result)
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result.area = area
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result.xmax = float(width - 1)
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result.ymax = float(height - 1)
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result.center = (result.xmax * 0.5, result.ymax * 0.5)
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#---------------------------------------------------------------------------------------------------
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func δ(r, θ: float): Vec2 = (r * cos(degToRad(θ)), r * sin(degToRad(θ)))
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#---------------------------------------------------------------------------------------------------
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func nextPoint(p: Point; r, θ: float): Point =
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let dp = δ(r, θ)
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result = (p.x + dp.x, p.y + dp.y)
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#---------------------------------------------------------------------------------------------------
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proc draw(sim: Simulation; context: cairo.Context) =
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## Draw the spiral.
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context.setSource(Black)
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context.rectangle(0, 0, sim.xmax, sim.ymax)
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context.fill()
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let colorIndex = sim.itercount mod Colors.len
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let color = Colors[colorIndex]
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var p1 = sim.center
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let δθ = Angles[sim.itercount mod Angles.len].toFloat
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var θ = δθ * rand(1.0) * 3
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var r = 5.0
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let δr = 3.0
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for _ in 1..DrawIters:
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let p2 = p1.nextPoint(r, θ)
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context.moveTo(p1.x, p1.y)
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context.setSource(color)
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context.lineTo(p2.x, p2.y)
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context.setLineWidth(2)
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context.stroke()
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θ += δθ
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r += δr
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p1 = p2
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#---------------------------------------------------------------------------------------------------
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proc update(sim: Simulation): gboolean =
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## Update the simulation state.
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result = gboolean(1)
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sim.draw(sim.area.window.cairoCreate())
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inc sim.itercount
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#---------------------------------------------------------------------------------------------------
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proc activate(app: Application) =
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## Activate the application.
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let window = app.newApplicationWindow()
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window.setSizeRequest(Width, Height)
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window.setTitle("Polyspiral")
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let area = newDrawingArea()
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window.add(area)
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let sim = newSimulation(area, Width, Height)
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timeoutAdd(500, update, sim)
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window.showAll()
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#———————————————————————————————————————————————————————————————————————————————————————————————————
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let app = newApplication(Application, "Rosetta.polyspiral")
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discard app.connect("activate", activate)
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discard app.run()
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