June 2018 Update

Task/Animate-a-pendulum/Lingo/animate-a-pendulum.lingo

@@ -0,0 +1,43 @@
+global RODLEN, GRAVITY, DT
+global velocity, acceleration, angle, posX, posY
+
+on startMovie
+
+    -- window properties
+    _movie.stage.title = "Pendulum"
+    _movie.stage.titlebarOptions.visible = TRUE
+    _movie.stage.rect = rect(0, 0, 400, 400)
+    _movie.centerStage = TRUE
+    _movie.puppetTempo(30)
+
+    RODLEN = 180
+    GRAVITY = -9.8
+    DT = 0.03
+
+    velocity = 0.0
+    acceleration = 0.0
+    angle = PI/3
+    posX = 200 - sin(angle) * RODLEN
+    posY = 100 + cos(angle) * RODLEN
+    paint()
+
+    -- show the window
+    _movie.stage.visible = TRUE
+end
+
+on enterFrame
+    acceleration = GRAVITY * sin(angle)
+    velocity = velocity + acceleration * DT
+    angle = angle + velocity * DT
+    posX = 200 - sin(angle) * rodLen
+    posY = 100 + cos(angle) * rodLen
+    paint()
+end
+
+on paint
+    img = _movie.stage.image
+    img.fill(img.rect, rgb(255,255,255))
+    img.fill(point(200-5, 100-5), point(200+5, 100+5), [#shapeType:#oval,#color:rgb(0,0,0)])
+    img.draw(point(200, 100), point(posX, posY), [#color:rgb(0,0,0)])
+    img.fill(point(posX-20, posY-20), point(posX+20, posY+20), [#shapeType:#oval,#lineSize:1,#bgColor:rgb(0,0,0),#color:rgb(255,255,0)])
+end