var builder = new function(){
	var base = this
	
	var els = []

	base.init = function(){
		base.bind()
	}

	base.bind = function(){
		app.on("clip", rebuild)
	}

	function rebuild(){
		if (window.scene) {
			clear()
			build()
			bind()
		}
	}
	function build (){
		clipper.rooms = sort_rooms_by_id(clipper.rooms)

		clipper.regions.forEach(function(r){
			build_walls(r).forEach(function(el){
				els.push(el)
				scene.add(el)
			})
		})

		clipper.rooms = sort_rooms_by_height(clipper.rooms)
		clipper.rooms.forEach(function(r){
			build_floors(r).forEach(function(el){
				els.push(el)
				scene.add(el)
			})
		})
	}
	
	function bind (){
		clipper.rooms.forEach(function(r){
			r.bind()
		})
	}
	
	function clear (){
		els.forEach(function(el){
			scene.remove(el)
		})
		els = []
	}

	function build_walls (r){
		var rm = clipper.rooms[ r.id ]
		
		var list = [], el = null
		
		var width = r.x.length()
		var depth = r.y.length()
		var height = clipper.rooms[r.id].height

		if (r.sides & FRONT) {
			el = make_wall('.front')
			el.width = width
			el.height = height
			el.rotationY = PI
			el.x = r.x.a + width/2
			el.y = height/2
			el.z = r.y.a
			rm.$walls.push(el.el)
			list.push(el)
		}
		if (r.sides & BACK) {
			var el = make_wall('.back')
			el.width = width
			el.height = height
			el.rotationY = 0
			el.x = r.x.b - width/2
			el.y = height/2
			el.z = r.y.b
			rm.$walls.push(el.el)
			list.push(el)
		}
		if (r.sides & LEFT) {
			el = make_wall('.left')
			el.rotationY = HALF_PI
			el.height = height
			el.width = depth
			el.x = r.x.a
			el.y = height/2
			el.z = r.y.a + depth/2
			rm.$walls.push(el.el)
			list.push(el)
		}
		if (r.sides & RIGHT) {
			el = make_wall('.right')
			el.rotationY = -HALF_PI
			el.height = height
			el.width = depth
			el.x = r.x.b
			el.y = height/2
			el.z = r.y.b - depth/2
			rm.$walls.push(el.el)
			list.push(el)
		}

		return list
	}

	function build_floors(rm){
		var list = [], el = null
		
		var already_constructed = rm.intersects.filter(function(rr){ return rr.constructed })
		sort_rooms_by_height(already_constructed)
		
		if (already_constructed.length > 0) {
			// render the regions that don't intersect with anything we've already rendered
			// if the height is different, calculate the overlapping sides and render half-walls
			rm.regions.forEach(function(r){
				var intersected = false
				for (var i = 0; i < already_constructed.length; i++) {
					if (already_constructed[i].rect.contains(r)) {
						intersected = true
						// r.sides = 0xf
						// half_sides
					}
					else if (already_constructed[i].rect.intersects(r)) {
						intersected = true
						if (rm.height < already_constructed[i].height) {
							list = list.concat( make_ceiling_walls( rm, already_constructed[i], r ) )
						}
					}
				}
				if (! intersected) {
					el = make_floor(rm, r) 
					list.push( el )
					rm.$floor.push(el.el)

					el = make_ceiling(rm, r) 
					list.push( el )
					rm.$ceiling.push(el.el)
				}
			})

		}
		else {
			// render floor and ceiling for the entire rectangle
			el = make_floor(rm, rm.rect) 
			list.push( el )
			rm.$floor.push(el.el)

			el = make_ceiling(rm, rm.rect) 
			list.push( el )
			rm.$ceiling.push(el.el)
		}
		
		rm.constructed = true
		return list
	}
	
	function make_ceiling_walls( lo, hi, r ){
		var list = []
		
		var width = r.x.length()
		var depth = r.y.length()
		var height = hi.height - lo.height
		
		if (! (r.half_sides & LEFT) && r.x.a == hi.rect.x.a) {
			el = make_wall('.left')
			el.rotationY = HALF_PI
			el.height = height
			el.width = depth
			el.x = r.x.a
			el.y = lo.height + height/2
			el.z = r.y.a + depth/2
			list.push(el)
			hi.$walls.push(el.el)
			r.half_sides |= LEFT
		}

		if (! (r.half_sides & RIGHT) && r.x.b == hi.rect.x.b) {
			el = make_wall('.right')
			el.rotationY = -HALF_PI
			el.height = height
			el.width = depth
			el.x = r.x.b
			el.y = lo.height + height/2
			el.z = r.y.b - depth/2
			list.push(el)
			hi.$walls.push(el.el)
			r.half_sides |= RIGHT
		}

		if (! (r.half_sides & FRONT) && r.y.a == hi.rect.y.a) {
			el = make_wall('.front')
			el.width = width
			el.height = height
			el.rotationY = PI
			el.x = r.x.a + width/2
			el.y = lo.height + height/2
			el.z = r.y.a
			list.push(el)
			hi.$walls.push(el.el)
			r.half_sides |= FRONT
		}

		if (! (r.half_sides & BACK) && r.y.b == hi.rect.y.b) {
			el = make_wall('.back')
			el.width = width
			el.height = height
			el.rotationY = 0
			el.x = r.x.b - width/2
			el.y = lo.height + height/2
			el.z = r.y.b
			list.push(el)
			hi.$walls.push(el.el)
			r.half_sides |= BACK
		}
		return list
	}

	function make_floor(rm, r){
		var width = r.x.length()
		var depth = r.y.length()
		
		var el = make_wall('.floor')
		el.height = depth
		el.width = width
		el.x = r.x.a + width/2
		el.y = 0
		el.z = r.y.a + depth/2
		el.rotationX = PI/2
		
		return el
	}
	function make_ceiling(rm, r){
		var width = r.x.length()
		var depth = r.y.length()
		var height = rm.height

		var el = make_wall('.ceiling')
		el.height = depth
		el.width = width
		el.x = r.x.a + width/2
		el.y = height
		el.z = r.y.a + depth/2
		el.rotationX = -PI/2
		return el
	}

	function make_wall(klass){
		var el = new MX.Object3D(".face" + (klass || ""))
		el.width = el.height = el.scaleX = el.scaleY = el.scaleZ = 1
		el.z = el.y = el.x = 0
		el.type = "Face"
		el.el.style.opacity = 1.0
		return el
	}

}