diff --git a/include/components/layer.hpp b/include/components/layer.hpp
index 28819f2..7a368bc 100644
--- a/include/components/layer.hpp
+++ b/include/components/layer.hpp
@@ -8,7 +8,7 @@
 #include <vector>
 
 namespace dk {
-	template <typename T, size_t D>
+	template <size_t D>
 	class Viewport;
 
 	template <size_t D>
@@ -19,6 +19,9 @@ namespace dk {
 		LayerBase ( const coords& parCount, const coords& parTileSize, const coords& parMasterTileSize );
 		virtual ~LayerBase ( void ) noexcept = default;
 
+		virtual void preload ( const coords& parFrom, const coords& parTo ) = 0;
+		coords count ( void ) const { return m_mastersize / m_tilesize * m_count; }
+
 	protected:
 		coords m_count;
 		coords m_tilesize;
@@ -27,6 +30,8 @@ namespace dk {
 
 	template <typename T, size_t D>
 	class Layer : public LayerBase<D> {
+		friend class Viewport<D>;
+
 	public:
 		typedef typename LayerBase<D>::coords coords;
 		typedef TileStreamer<T, D> streamer_type;
@@ -40,11 +45,11 @@ namespace dk {
 		Layer& operator= ( const Layer& ) = delete;
 
 		iterator begin ( void );
-		void setActiveViewport ( const coords& parFrom, const coords& parCount );
+		iterator end ( void );
+		virtual void preload ( const coords& parFrom, const coords& parTo );
 
 	private:
 		streamer_type m_streamer;
-		Viewport<T, D> m_activeViewport;
 		std::vector<T> m_tiles;
 	};
 
diff --git a/include/components/tileiterator.hpp b/include/components/tileiterator.hpp
index 02ed2b0..ee61f7e 100644
--- a/include/components/tileiterator.hpp
+++ b/include/components/tileiterator.hpp
@@ -9,12 +9,15 @@
 namespace dk {
 	namespace implem {
 		template <size_t D>
-		inline size_t get_index_from_pos ( const Vector<CoordinateScalarType, D>& parPos, const Vector<CoordinateScalarType, D>& parSize ) a_pure;
+		size_t get_index_from_pos ( const Vector<CoordinateScalarType, D>& parPos, const Vector<CoordinateScalarType, D>& parSize ) a_pure;
 
 #if defined(NDEBUG)
 		template <>
-		inline size_t get_index_from_pos<2> ( const Vector<CoordinateScalarType, 2>& parPos, const Vector<CoordinateScalarType, 2>& parSize ) a_pure;
+		size_t get_index_from_pos<2> ( const Vector<CoordinateScalarType, 2>& parPos, const Vector<CoordinateScalarType, 2>& parSize ) a_pure;
 #endif
+
+		template <size_t D>
+		Vector<CoordinateScalarType, D> buildPastEndCoordinate ( const Vector<CoordinateScalarType, D>& parFrom, const Vector<CoordinateScalarType, D>& parTo ) a_pure;
 	} //namespace implem
 
 	template <typename T, size_t D>
@@ -26,7 +29,7 @@ namespace dk {
 		TileIterator ( void );
 		TileIterator ( const TileIterator& parOther ) = default;
 		TileIterator ( std::vector<T>* parData, const coords& parFrom, const coords& parTo );
-		TileIterator ( std::vector<T>* parData, const coords& parFrom, const coords& parTo, const coords& parAreaFrom, const coords& parAreaTo, const coords& parTotal );
+		TileIterator ( std::vector<T>* parData, const coords& parFrom, const coords& parTo, const coords& parAreaFrom, const coords& parAreaTo );
 		~TileIterator ( void ) = default;
 
 		const coords& position ( void ) const { return m_pos; }
@@ -38,14 +41,13 @@ namespace dk {
 		ptrdiff_t distance_to ( const TileIterator& parOther );
 		bool equal ( const TileIterator& parOther ) const;
 		T& dereference ( void ) const { return (*m_data)[get_current_index()]; }
-		size_t get_current_index ( void ) const { return implem::get_index_from_pos<D>(m_pos, m_total); }
+		size_t get_current_index ( void ) const { return implem::get_index_from_pos<D>(m_pos, m_areato - m_areafrom); }
 
 		coords m_pos;
 		coords m_from;
 		coords m_to;
 		coords m_areafrom;
 		coords m_areato;
-		coords m_total;
 		std::vector<T>* m_data;
 	};
 } //namespace dk
diff --git a/include/components/tyler.hpp b/include/components/tyler.hpp
index e3844bf..efd9aea 100644
--- a/include/components/tyler.hpp
+++ b/include/components/tyler.hpp
@@ -27,6 +27,8 @@ namespace dk {
 		template <typename T>
 		Layer<T, D>& push_layer ( typename Layer<T, D>::streamer_type&& parStreamer, const coords& parSubdiv );
 
+		void preload ( const coords& parFrom, const coords& parTo );
+
 	private:
 		const coords m_size;
 		const coords m_tilesize;
diff --git a/include/components/viewport.hpp b/include/components/viewport.hpp
index 5c35f61..68834a0 100644
--- a/include/components/viewport.hpp
+++ b/include/components/viewport.hpp
@@ -6,28 +6,36 @@
 #include "components/layer.hpp"
 
 namespace dk {
+	template <size_t D>
+	class Tyler;
+
 	template <typename T, size_t D>
 	class Layer;
 
-	template <typename T, size_t D>
+	template <size_t D>
 	class Viewport {
 	public:
 		typedef Vector<CoordinateScalarType, D> coords;
-		typedef typename Layer<T, D>::iterator iterator;
 
-		explicit Viewport ( Layer<T, D>& parLayer );
-		Viewport ( Layer<T, D>& parLayer, const coords& parSize, const coords& parPos );
+		explicit Viewport ( Tyler<D>& parTyler );
+		Viewport ( Tyler<D>& parTyler, const coords& parSize, const coords& parPos );
 		~Viewport ( void ) noexcept = default;
 
 		Viewport& operator= ( const Viewport& ) = default;
 
-		void setSize ( const coords& parSize ) { m_size = parSize; }
-		void setFrom ( const coords& parFrom ) { m_position = parFrom; }
+		void setSize ( const coords& parSize );
+		void setFrom ( const coords& parFrom );
+		void setFromSize ( const coords& parFrom, const coords& parSize );
+
+		template <typename T>
+		typename Layer<T, D>::iterator begin ( Layer<T, D>& parLayer ) const;
+		template <typename T>
+		typename Layer<T, D>::iterator end ( Layer<T, D>& parLayer ) const;
 
 	private:
 		coords m_size;
 		coords m_position;
-		Layer<T, D>& m_layer;
+		Tyler<D>& m_tyler;
 	};
 } //namespace dk
 
diff --git a/include/implem/layer.inl b/include/implem/layer.inl
index 3b9202d..dbdb853 100644
--- a/include/implem/layer.inl
+++ b/include/implem/layer.inl
@@ -28,11 +28,9 @@ namespace dk {
 	template <typename T, size_t D>
 	Layer<T, D>::Layer (const coords& parCount, const coords& parTileSize, const coords& parMasterTileSize, streamer_type&& parStreamer) :
 		LayerBase<D>(parCount, parTileSize, parMasterTileSize),
-		m_streamer(std::move(parStreamer)),
-		m_activeViewport(*this)
+		m_streamer(std::move(parStreamer))
 	{
 		DK_ASSERT(m_streamer.tilesCount() == this->m_count);
-		setActiveViewport(coords(0), parCount);
 	}
 
 	///--------------------------------------------------------------------------
@@ -45,12 +43,17 @@ namespace dk {
 	///--------------------------------------------------------------------------
 	///--------------------------------------------------------------------------
 	template <typename T, size_t D>
-	void Layer<T, D>::setActiveViewport (const coords& parFrom, const coords& parCount) {
+	typename Layer<T, D>::iterator Layer<T, D>::end() {
+		return iterator(&m_tiles, implem::buildPastEndCoordinate<D>(coords(0), this->m_count), this->m_count);
+	}
+
+	///--------------------------------------------------------------------------
+	///--------------------------------------------------------------------------
+	template <typename T, size_t D>
+	void Layer<T, D>::preload (const coords& parFrom, const coords& parTo) {
 		m_tiles.clear();
-		const auto area = implem::area<D>(parCount);
+		const auto area = implem::area<D>(parTo - parFrom);
 		m_tiles.reserve(area);
-		m_streamer.copy(m_tiles, parFrom, parFrom + parCount);
-		m_activeViewport.setFrom(parFrom);
-		m_activeViewport.setSize(parCount);
+		m_streamer.copy(m_tiles, parFrom, parTo);
 	}
 }
diff --git a/include/implem/tileiterator.inl b/include/implem/tileiterator.inl
index 88e3743..57b5633 100644
--- a/include/implem/tileiterator.inl
+++ b/include/implem/tileiterator.inl
@@ -20,6 +20,16 @@ namespace dk {
 			return parPos.y() * parSize.x() + parPos.x();
 		}
 #endif
+
+		template <size_t D>
+		inline Vector<CoordinateScalarType, D> buildPastEndCoordinate (const Vector<CoordinateScalarType, D>& parFrom, const Vector<CoordinateScalarType, D>& parTo) {
+			Vector<CoordinateScalarType, D> retval;
+			for (size_t d = 0; d < D - 1; ++d) {
+				retval[d] = parFrom[d];
+			}
+			retval[D - 1] = parTo[D - 1];
+			return retval;
+		}
 	} //namespace implem
 
 	template <typename T, size_t D>
@@ -29,7 +39,6 @@ namespace dk {
 		m_to(CoordinateScalarType()),
 		m_areafrom(CoordinateScalarType()),
 		m_areato(CoordinateScalarType()),
-		m_total(CoordinateScalarType()),
 		m_data(nullptr)
 	{
 	}
@@ -41,20 +50,18 @@ namespace dk {
 		m_to(parTo),
 		m_areafrom(parFrom),
 		m_areato(parTo),
-		m_total(parTo - parFrom),
 		m_data(parData)
 	{
 		DK_ASSERT(parData);
 	}
 
 	template <typename T, size_t D>
-	TileIterator<T, D>::TileIterator (std::vector<T>* parData, const coords& parFrom, const coords& parTo, const coords& parAreaFrom, const coords& parAreaTo, const coords& parTotal) :
+	TileIterator<T, D>::TileIterator (std::vector<T>* parData, const coords& parFrom, const coords& parTo, const coords& parAreaFrom, const coords& parAreaTo) :
 		m_pos(parFrom),
 		m_from(parFrom),
 		m_to(parTo),
 		m_areafrom(parAreaFrom),
 		m_areato(parAreaTo),
-		m_total(parTotal),
 		m_data(parData)
 	{
 		DK_ASSERT(parData);
diff --git a/include/implem/tyler.inl b/include/implem/tyler.inl
index ab65344..3fb6907 100644
--- a/include/implem/tyler.inl
+++ b/include/implem/tyler.inl
@@ -39,4 +39,13 @@ namespace dk {
 		m_layers.push_back(LayerPtr(newLayer));
 		return *newLayer;
 	}
+
+	///--------------------------------------------------------------------------
+	///--------------------------------------------------------------------------
+	template <size_t D>
+	void Tyler<D>::preload (const coords& parFrom, const coords& parTo) {
+		for (auto& layer : m_layers) {
+			layer->preload(parFrom, parTo);
+		}
+	}
 } //namespace dk
diff --git a/include/implem/viewport.inl b/include/implem/viewport.inl
index c0fb04b..9c0bd68 100644
--- a/include/implem/viewport.inl
+++ b/include/implem/viewport.inl
@@ -1,15 +1,52 @@
 namespace dk {
-	template <typename T, size_t D>
-	Viewport<T, D>::Viewport (Layer<T, D>& parLayer) :
-		m_layer(parLayer)
+	template <size_t D>
+	Viewport<D>::Viewport (Tyler<D>& parTyler) :
+		m_tyler(parTyler)
 	{
 	}
 
-	template <typename T, size_t D>
-	Viewport<T, D>::Viewport (Layer<T, D>& parLayer, const coords& parSize, const coords& parPos) :
+	template <size_t D>
+	Viewport<D>::Viewport (Tyler<D>& parTyler, const coords& parSize, const coords& parPos) :
 		m_size(parSize),
 		m_position(parPos),
-		m_layer(parLayer)
+		m_tyler(parTyler)
 	{
+		m_tyler.preload(m_position, m_position + m_size);
+	}
+
+	template <size_t D>
+	template <typename T>
+	typename Layer<T, D>::iterator Viewport<D>::begin (Layer<T, D>& parLayer) const {
+		typedef typename Layer<T, D>::iterator IterType;
+
+		return IterType(&parLayer.m_tiles, m_position, m_position + m_size);
+	}
+
+	template <size_t D>
+	template <typename T>
+	typename Layer<T, D>::iterator Viewport<D>::end (Layer<T, D>& parLayer) const {
+		typedef typename Layer<T, D>::iterator IterType;
+
+		const auto to(m_position + m_size);
+		return IterType(&parLayer.m_tiles, implem::buildPastEndCoordinate(m_position, to), to);
+	}
+
+	template <size_t D>
+	void Viewport<D>::setSize (const coords& parSize) {
+		m_size = parSize;
+		m_tyler.preload(m_position, m_position + m_size);
+	}
+
+	template <size_t D>
+	void Viewport<D>::setFrom (const coords& parFrom) {
+		m_position = parFrom;
+		m_tyler.preload(m_position, m_position + m_size);
+	}
+
+	template <size_t D>
+	void Viewport<D>::setFromSize (const coords& parFrom, const coords& parSize) {
+		m_position = parFrom;
+		m_size = parSize;
+		m_tyler.preload(m_position, m_position + m_size);
 	}
 } //namespace dk
diff --git a/src/main.cpp b/src/main.cpp
index 5e40e71..d735d78 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -15,16 +15,21 @@ int main() {
 
 	std::cout << "Loading " << map1 << '\n';
 	auto bottom_layer = &tiler.push_layer<int>(dk::Layer<int, 2>::streamer_type(ifstreamptr(new std::ifstream(map1))));
-	std::cout << "Loading " << map2 << '\n';
-	tiler.push_layer<char>(dk::Layer<char, 2>::streamer_type(ifstreamptr(new std::ifstream(map2))), dk::Vector<int, 2>(2));
+	//std::cout << "Loading " << map2 << '\n';
+	//tiler.push_layer<char>(dk::Layer<char, 2>::streamer_type(ifstreamptr(new std::ifstream(map2))), dk::Vector<int, 2>(2));
 
+	dk::Viewport<2> viewport(tiler, Tiler::coords(0), Tiler::coords(10, 6));
+	dk::Viewport<2> viewport_small(tiler, Tiler::coords(1), Tiler::coords(9, 5));
 	{
-		auto ittest = bottom_layer->begin();
-		for (int z = 0; z < 10; ++z) {
-#if !defined(NDEBUG)
-			std::cout << "At tile " << ittest.position() << " value " << *ittest << '\n';
-#endif
-			++ittest;
+		int col = 0;
+		const auto tilecount = bottom_layer->count();
+		for (auto tile : *bottom_layer) {
+			std::cout << tile;
+			++col;
+			if (col == tilecount.x()) {
+				col = 0;
+				std::cout << '\n';
+			}
 		}
 	}