added visibility flag to Engine::Object and ag::object::setVisible() to control it

git-svn-id: svn://anubis/anaglym/trunk@68 99a6e188-d820-4881-8870-2d33a10e2619

tests/ballstairs.lua

@@ -1,10 +1,5 @@
 
 function update()
-    elapsed = ag.elapsedTime()
-    if (elapsed > 2000 and ball2there) then
-        ball2:destroy()
-        ball2there = false
-    end
     ballx, bally, ballz = ball:getPosition()
     ag.setCamera(7, -6, 15, ballx, bally, ballz, 0, 0, 1)
     ag.doPhysics()
@@ -15,11 +10,11 @@ end
 
 --ag.setCamera(8, -8, 15, -8, 8, 4, 0, 0, 1)
 arena = ag.loadStaticModel("boxarena")
+arena:setVisible(false)
 ball = ag.loadModel("ball")
 ball:setPosition(-7, 7.4, 12)
 ball2 = ball:clone()
 ball2:setPosition(-7, 7.4, 14)
-ball2there = true
 ball3 = ball:clone()
 ball3:setPosition(-7, 7.4, 16)
 logo = ag.loadModel("dwlogo")