September 2017 Update

Task/Animate-a-pendulum/Lua/animate-a-pendulum.lua

@@ -0,0 +1,28 @@
+function degToRad( d )
+    return d * 0.01745329251
+end
+
+function love.load()
+    g = love.graphics
+    rodLen, gravity, velocity, acceleration = 260, 3, 0, 0
+    halfWid, damp = g.getWidth() / 2, .989
+    posX, posY, angle = halfWid
+    TWO_PI, angle = math.pi * 2, degToRad( 90 )
+end
+
+function love.update( dt )
+    acceleration = -gravity / rodLen * math.sin( angle )
+    angle = angle + velocity; if angle > TWO_PI then angle = 0 end
+    velocity = velocity + acceleration
+    velocity = velocity * damp
+    posX = halfWid + math.sin( angle ) * rodLen
+    posY = math.cos( angle ) * rodLen
+end
+
+function love.draw()
+    g.setColor( 250, 0, 250 )
+    g.circle( "fill", halfWid, 0, 8 )
+    g.line( halfWid, 4, posX, posY )
+    g.setColor( 250, 100, 20 )
+    g.circle( "fill", posX, posY, 20 )
+end