/*
-----------------------------------------------------------------------------
This source file is part of OGRE
(Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org

Copyright (c) 2000-2009 Torus Knot Software Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
-----------------------------------------------------------------------------
*/
#ifndef __RenderSystem_H_
#define __RenderSystem_H_

// Precompiler options
#include "OgrePrerequisites.h"

#include "OgreString.h"

#include "OgreTextureUnitState.h"
#include "OgreCommon.h"

#include "OgreRenderOperation.h"
#include "OgreRenderSystemCapabilities.h"
#include "OgreRenderTarget.h"
#include "OgreRenderTexture.h"
#include "OgreFrameListener.h"
#include "OgreConfigOptionMap.h"
#include "OgreGpuProgram.h"
#include "OgrePlane.h"
#include "OgreIteratorWrappers.h"

namespace Ogre
{
	/** \addtogroup Core
	*  @{
	*/
	/** \addtogroup RenderSystem
	*  @{
	*/

	typedef map< String, RenderTarget * >::type RenderTargetMap;
	typedef multimap<uchar, RenderTarget * >::type RenderTargetPriorityMap;

	class TextureManager;
	/// Enum describing the ways to generate texture coordinates
	enum TexCoordCalcMethod
	{
		/// No calculated texture coordinates
		TEXCALC_NONE,
		/// Environment map based on vertex normals
		TEXCALC_ENVIRONMENT_MAP,
		/// Environment map based on vertex positions
		TEXCALC_ENVIRONMENT_MAP_PLANAR,
		TEXCALC_ENVIRONMENT_MAP_REFLECTION,
		TEXCALC_ENVIRONMENT_MAP_NORMAL,
		/// Projective texture
		TEXCALC_PROJECTIVE_TEXTURE
	};
	/// Enum describing the various actions which can be taken onthe stencil buffer
	enum StencilOperation
	{
		/// Leave the stencil buffer unchanged
		SOP_KEEP,
		/// Set the stencil value to zero
		SOP_ZERO,
		/// Set the stencil value to the reference value
		SOP_REPLACE,
		/// Increase the stencil value by 1, clamping at the maximum value
		SOP_INCREMENT,
		/// Decrease the stencil value by 1, clamping at 0
		SOP_DECREMENT,
		/// Increase the stencil value by 1, wrapping back to 0 when incrementing the maximum value
		SOP_INCREMENT_WRAP,
		/// Decrease the stencil value by 1, wrapping when decrementing 0
		SOP_DECREMENT_WRAP,
		/// Invert the bits of the stencil buffer
		SOP_INVERT
	};


	/** Defines the functionality of a 3D API
	@remarks
	The RenderSystem class provides a base interface
	which abstracts the general functionality of the 3D API
	e.g. Direct3D or OpenGL. Whilst a few of the general
	methods have implementations, most of this class is
	abstract, requiring a subclass based on a specific API
	to be constructed to provide the full functionality.
	Note there are 2 levels to the interface - one which
	will be used often by the caller of the Ogre library,
	and one which is at a lower level and will be used by the
	other classes provided by Ogre. These lower level
	methods are prefixed with '_' to differentiate them.
	The advanced user of the library may use these lower
	level methods to access the 3D API at a more fundamental
	level (dealing direct with render states and rendering
	primitives), but still benefiting from Ogre's abstraction
	of exactly which 3D API is in use.
	@author
	Steven Streeting
	@version
	1.0
	*/
	class _OgreExport RenderSystem : public RenderSysAlloc
	{
	public:
		/** Default Constructor.
		*/
		RenderSystem();

		/** Destructor.
		*/
		virtual ~RenderSystem();

		/** Returns the name of the rendering system.
		*/
		virtual const String& getName(void) const = 0;

		/** Returns the details of this API's configuration options
		@remarks
		Each render system must be able to inform the world
		of what options must/can be specified for it's
		operation.
		@par
		These are passed as strings for portability, but
		grouped into a structure (_ConfigOption) which includes
		both options and current value.
		@par
		Note that the settings returned from this call are
		affected by the options that have been set so far,
		since some options are interdependent.
		@par
		This routine is called automatically by the default
		configuration dialogue produced by Root::showConfigDialog
		or may be used by the caller for custom settings dialogs
		@returns
		A 'map' of options, i.e. a list of options which is also
		indexed by option name.
		*/
		virtual ConfigOptionMap& getConfigOptions(void) = 0;

		/** Sets an option for this API
		@remarks
		Used to confirm the settings (normally chosen by the user) in
		order to make the renderer able to initialise with the settings as required.
		This may be video mode, D3D driver, full screen / windowed etc.
		Called automatically by the default configuration
		dialog, and by the restoration of saved settings.
		These settings are stored and only activated when
		RenderSystem::initialise or RenderSystem::reinitialise
		are called.
		@par
		If using a custom configuration dialog, it is advised that the
		caller calls RenderSystem::getConfigOptions
		again, since some options can alter resulting from a selection.
		@param
		name The name of the option to alter.
		@param
		value The value to set the option to.
		*/
		virtual void setConfigOption(const String &name, const String &value) = 0;

		/** Create an object for performing hardware occlusion queries. 
		*/
		virtual HardwareOcclusionQuery* createHardwareOcclusionQuery(void) = 0;

		/** Destroy a hardware occlusion query object. 
		*/
		virtual void destroyHardwareOcclusionQuery(HardwareOcclusionQuery *hq);

		/** Validates the options set for the rendering system, returning a message if there are problems.
		@note
		If the returned string is empty, there are no problems.
		*/
		virtual String validateConfigOptions(void) = 0;

		/** Start up the renderer using the settings selected (Or the defaults if none have been selected).
		@remarks
		Called by Root::setRenderSystem. Shouldn't really be called
		directly, although  this can be done if the app wants to.
		@param
		autoCreateWindow If true, creates a render window
		automatically, based on settings chosen so far. This saves
		an extra call to _createRenderWindow
		for the main render window.
		@par
		If an application has more specific window requirements,
		however (e.g. a level design app), it should specify false
		for this parameter and do it manually.
		@returns
		A pointer to the automatically created window, if requested, otherwise null.
		*/
		virtual RenderWindow* _initialise(bool autoCreateWindow, const String& windowTitle = "OGRE Render Window");


		/** Query the real capabilities of the GPU and driver in the RenderSystem*/
		virtual RenderSystemCapabilities* createRenderSystemCapabilities() const = 0;

		/** Force the render system to use the special capabilities. Can only be called
		*    before the render system has been fully initializer (before createWindow is called) 
		*	@param
		*		 capabilities has to be a subset of the real capabilities and the caller is 
		*		 responsible for deallocating capabilities.
		*/
		virtual void useCustomRenderSystemCapabilities(RenderSystemCapabilities* capabilities);

		/** Restart the renderer (normally following a change in settings).
		*/
		virtual void reinitialise(void) = 0;

		/** Shutdown the renderer and cleanup resources.
		*/
		virtual void shutdown(void);


		/** Sets the colour & strength of the ambient (global directionless) light in the world.
		*/
		virtual void setAmbientLight(float r, float g, float b) = 0;

		/** Sets the type of light shading required (default = Gouraud).
		*/
		virtual void setShadingType(ShadeOptions so) = 0;

		/** Sets whether or not dynamic lighting is enabled.
		@param
		enabled If true, dynamic lighting is performed on geometry with normals supplied, geometry without
		normals will not be displayed. If false, no lighting is applied and all geometry will be full brightness.
		*/
		virtual void setLightingEnabled(bool enabled) = 0;

		/** Sets whether or not W-buffers are enabled if they are available for this renderer.
		@param
		enabled If true and the renderer supports them W-buffers will be used.  If false 
		W-buffers will not be used even if available.  W-buffers are enabled by default 
		for 16bit depth buffers and disabled for all other depths.
		*/
		void setWBufferEnabled(bool enabled);

		/** Returns true if the renderer will try to use W-buffers when avalible.
		*/
		bool getWBufferEnabled(void) const;

		/** Creates a new rendering window.
		@remarks
		This method creates a new rendering window as specified
		by the paramteters. The rendering system could be
		responible for only a single window (e.g. in the case
		of a game), or could be in charge of multiple ones (in the
		case of a level editor). The option to create the window
		as a child of another is therefore given.
		This method will create an appropriate subclass of
		RenderWindow depending on the API and platform implementation.
		@par
		After creation, this window can be retrieved using getRenderTarget().
		@param
		name The name of the window. Used in other methods
		later like setRenderTarget and getRenderTarget.
		@param
		width The width of the new window.
		@param
		height The height of the new window.
		@param
		fullScreen Specify true to make the window full screen
		without borders, title bar or menu bar.
		@param
		miscParams A NameValuePairList describing the other parameters for the new rendering window. 
		Options are case sensitive. Unrecognised parameters will be ignored silently.
		These values might be platform dependent, but these are present for all platforms unless
		indicated otherwise:
		<table>
		<tr>
			<td><b>Key</b></td>
			<td><b>Type/Values</b></td>
			<td><b>Default</b></td>
			<td><b>Description</b></td>
			<td><b>Notes</b></td>
		</tr>
		<tr>
			<td>title</td>
			<td>Any string</td>
			<td>RenderTarget name</td>
			<td>The title of the window that will appear in the title bar</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>colourDepth</td>
			<td>16, 32</td>
			<td>Desktop depth</td>
			<td>Colour depth of the resulting rendering window; only applies if fullScreen</td>
			<td>Win32 Specific</td>
		</tr>
		<tr>
			<td>left</td>
			<td>Positive integers</td>
			<td>Centred</td>
			<td>Screen x coordinate from left</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>top</td>
			<td>Positive integers</td>
			<td>Centred</td>
			<td>Screen y coordinate from left</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>depthBuffer</td>
			<td>true, false</td>
			<td>true</td>
			<td>Use depth buffer</td>
			<td>DirectX9 specific</td>
		</tr>
		<tr>
			<td>externalWindowHandle</td>
			<td>Win32: HWND as integer<br/>
			    GLX: poslong:posint:poslong (display*:screen:windowHandle) or poslong:posint:poslong:poslong (display*:screen:windowHandle:XVisualInfo*)</td>
			<td>0 (none)</td>
			<td>External window handle, for embedding the OGRE render in an existing window</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>externalGLControl</td>
			<td>true, false</td>
			<td>false</td>
			<td>Let the external window control OpenGL i.e. don't select a pixel format for the window,
			do not change v-sync and do not swap buffer. When set to true, the calling application
			is responsible of OpenGL initialization and buffer swapping. It should also create an
			OpenGL context for its own rendering, Ogre will create one for its use. Then the calling
			application must also enable Ogre OpenGL context before calling any Ogre function and
			restore its OpenGL context after these calls.</td>
			<td>OpenGL specific</td>
		</tr>
		<tr>
			<td>externalGLContext</td>
			<td>Context as Unsigned Long</td>
			<td>0 (create own context)</td>
			<td>Use an externally created GL context</td>
			<td>OpenGL Specific</td>
		</tr>
		<tr>
			<td>parentWindowHandle</td>
			<td>Win32: HWND as integer<br/>
			    GLX: poslong:posint:poslong (display*:screen:windowHandle) or poslong:posint:poslong:poslong (display*:screen:windowHandle:XVisualInfo*)</td>
			<td>0 (none)</td>
			<td>Parent window handle, for embedding the OGRE in a child of an external window</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>macAPI</td>
			<td>String: "cocoa" or "carbon"</td>
			<td>"carbon"</td>
			<td>Specifies the type of rendering window on the Mac Platform.</td>
			<td>&nbsp;</td>
		 </tr>
		 <tr>
			<td>macAPICocoaUseNSView</td>
			<td>bool "true" or "false"</td>
			<td>"false"</td>
			<td>On the Mac platform the most diffused method to embed ogre in a custom application is to use the IntefaceBuilder
				and add to the interface an instance of OgreView.
				The pointer to this instance is then used as "externalWindowHandle".
				However, there are cases where you are NOT using the Interface Builder and you get the Cocoa NSView* of an existing interface.
				For example, this is happens when you want to render into a Java/AWT interface.
				In short, by setting this flag to "true" the Ogre::Root::createRenderWindow interprets the "externalWindowHandle" as a NSView*
				instead of an OgreView*. See OgreOSXCocoaView.h/mm.
			</td>
			<td>&nbsp;</td>
		 </tr>
         <tr>
             <td>contentScalingFactor</td>
             <td>Positive Float greater than 1.0</td>
             <td>The default content scaling factor of the screen</td>
             <td>Specifies the CAEAGLLayer content scaling factor.  Only supported on iOS 4 or greater.
                 This can be useful to limit the resolution of the OpenGL ES backing store.  For example, the iPhone 4's
                 native resolution is 960 x 640.  Windows are always 320 x 480, if you would like to limit the display
                 to 720 x 480, specify 1.5 as the scaling factor.
             </td>
             <td>&nbsp;</td>
		 </tr>
         <tr>
			<td>FSAA</td>
			<td>Positive integer (usually 0, 2, 4, 8, 16)</td>
			<td>0</td>
			<td>Full screen antialiasing factor</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>FSAAHint</td>
			<td>Depends on RenderSystem and hardware. Currently supports:<br/>
			"Quality": on systems that have an option to prefer higher AA quality over speed, use it</td>
			<td>Blank</td>
			<td>Full screen antialiasing hint</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>displayFrequency</td>
			<td>Refresh rate in Hertz (e.g. 60, 75, 100)</td>
			<td>Desktop vsync rate</td>
			<td>Display frequency rate, for fullscreen mode</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>vsync</td>
			<td>true, false</td>
			<td>false</td>
			<td>Synchronize buffer swaps to monitor vsync, eliminating tearing at the expense of a fixed frame rate</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>vsyncInterval</td>
			<td>1, 2, 3, 4</td>
			<td>1</td>
			<td>If vsync is enabled, the minimum number of vertical blanks that should occur between renders. 
			For example if vsync is enabled, the refresh rate is 60 and this is set to 2, then the
			frame rate will be locked at 30.</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>border</td>
			<td>none, fixed, resize</td>
			<td>resize</td>
			<td>The type of window border (in windowed mode)</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>outerDimensions</td>
			<td>true, false</td>
			<td>false</td>
			<td>Whether the width/height is expressed as the size of the 
			outer window, rather than the content area</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>useNVPerfHUD</td>
			<td>true, false</td>
			<td>false</td>
			<td>Enable the use of nVidia NVPerfHUD</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>gamma</td>
			<td>true, false</td>
			<td>false</td>
			<td>Enable hardware conversion from linear colour space to gamma
			colour space on rendering to the window.</td>
			<td>&nbsp;</td>
		</tr>
		*/
		virtual RenderWindow* _createRenderWindow(const String &name, unsigned int width, unsigned int height, 
			bool fullScreen, const NameValuePairList *miscParams = 0) = 0;

		/** Creates multiple rendering windows.		
		@param
		renderWindowDescriptions Array of structures containing the descriptions of each render window.
		The structure's members are the same as the parameters of _createRenderWindow:
		* name
		* width
		* height
		* fullScreen
		* miscParams
		See _createRenderWindow for details about each member.		
		@param
		createdWindows This array will hold the created render windows.
		@returns
		true on success.		
		*/
		virtual bool _createRenderWindows(const RenderWindowDescriptionList& renderWindowDescriptions, 
			RenderWindowList& createdWindows);

		
		/**	Create a MultiRenderTarget, which is a render target that renders to multiple RenderTextures
		at once. Surfaces can be bound and unbound at will.
		This fails if mCapabilities->getNumMultiRenderTargets() is smaller than 2.
		*/
		virtual MultiRenderTarget * createMultiRenderTarget(const String & name) = 0; 

		/** Destroys a render window */
		virtual void destroyRenderWindow(const String& name);
		/** Destroys a render texture */
		virtual void destroyRenderTexture(const String& name);
		/** Destroys a render target of any sort */
		virtual void destroyRenderTarget(const String& name);

		/** Attaches the passed render target to the render system.
		*/
		virtual void attachRenderTarget( RenderTarget &target );
		/** Returns a pointer to the render target with the passed name, or NULL if that
		render target cannot be found.
		*/
		virtual RenderTarget * getRenderTarget( const String &name );
		/** Detaches the render target with the passed name from the render system and
		returns a pointer to it.
		@note
		If the render target cannot be found, NULL is returned.
		*/
		virtual RenderTarget * detachRenderTarget( const String &name );

		/// Iterator over RenderTargets
		typedef MapIterator<Ogre::RenderTargetMap> RenderTargetIterator;

		/** Returns a specialised MapIterator over all render targets attached to the RenderSystem. */
		virtual RenderTargetIterator getRenderTargetIterator(void) {
			return RenderTargetIterator( mRenderTargets.begin(), mRenderTargets.end() );
		}
		/** Returns a description of an error code.
		*/
		virtual String getErrorDescription(long errorNumber) const = 0;

		/** Defines whether or now fullscreen render windows wait for the vertical blank before flipping buffers.
		@remarks
		By default, all rendering windows wait for a vertical blank (when the CRT beam turns off briefly to move
		from the bottom right of the screen back to the top left) before flipping the screen buffers. This ensures
		that the image you see on the screen is steady. However it restricts the frame rate to the refresh rate of
		the monitor, and can slow the frame rate down. You can speed this up by not waiting for the blank, but
		this has the downside of introducing 'tearing' artefacts where part of the previous frame is still displayed
		as the buffers are switched. Speed vs quality, you choose.
		@note
		Has NO effect on windowed mode render targets. Only affects fullscreen mode.
		@param
		enabled If true, the system waits for vertical blanks - quality over speed. If false it doesn't - speed over quality.
		*/
		void setWaitForVerticalBlank(bool enabled);

		/** Returns true if the system is synchronising frames with the monitor vertical blank.
		*/
		bool getWaitForVerticalBlank(void) const;

		// ------------------------------------------------------------------------
		//                     Internal Rendering Access
		// All methods below here are normally only called by other OGRE classes
		// They can be called by library user if required
		// ------------------------------------------------------------------------


		/** Tells the rendersystem to use the attached set of lights (and no others) 
		up to the number specified (this allows the same list to be used with different
		count limits) */
		virtual void _useLights(const LightList& lights, unsigned short limit) = 0;
		/** Are fixed-function lights provided in view space? Affects optimisation. 
		*/
		virtual bool areFixedFunctionLightsInViewSpace() const { return false; }
		/** Sets the world transform matrix. */
		virtual void _setWorldMatrix(const Matrix4 &m) = 0;
		/** Sets multiple world matrices (vertex blending). */
		virtual void _setWorldMatrices(const Matrix4* m, unsigned short count);
		/** Sets the view transform matrix */
		virtual void _setViewMatrix(const Matrix4 &m) = 0;
		/** Sets the projection transform matrix */
		virtual void _setProjectionMatrix(const Matrix4 &m) = 0;
		/** Utility function for setting all the properties of a texture unit at once.
		This method is also worth using over the individual texture unit settings because it
		only sets those settings which are different from the current settings for this
		unit, thus minimising render state changes.
		*/
		virtual void _setTextureUnitSettings(size_t texUnit, TextureUnitState& tl);
		/** Turns off a texture unit. */
		virtual void _disableTextureUnit(size_t texUnit);
		/** Disables all texture units from the given unit upwards */
		virtual void _disableTextureUnitsFrom(size_t texUnit);
		/** Sets the surface properties to be used for future rendering.

		This method sets the the properties of the surfaces of objects
		to be rendered after it. In this context these surface properties
		are the amount of each type of light the object reflects (determining
		it's colour under different types of light), whether it emits light
		itself, and how shiny it is. Textures are not dealt with here,
		see the _setTetxure method for details.
		This method is used by _setMaterial so does not need to be called
		direct if that method is being used.

		@param ambient The amount of ambient (sourceless and directionless)
		light an object reflects. Affected by the colour/amount of ambient light in the scene.
		@param diffuse The amount of light from directed sources that is
		reflected (affected by colour/amount of point, directed and spot light sources)
		@param specular The amount of specular light reflected. This is also
		affected by directed light sources but represents the colour at the
		highlights of the object.
		@param emissive The colour of light emitted from the object. Note that
		this will make an object seem brighter and not dependent on lights in
		the scene, but it will not act as a light, so will not illuminate other
		objects. Use a light attached to the same SceneNode as the object for this purpose.
		@param shininess A value which only has an effect on specular highlights (so
		specular must be non-black). The higher this value, the smaller and crisper the
		specular highlights will be, imitating a more highly polished surface.
		This value is not constrained to 0.0-1.0, in fact it is likely to
		be more (10.0 gives a modest sheen to an object).
		@param tracking A bit field that describes which of the ambient, diffuse, specular
		and emissive colours follow the vertex colour of the primitive. When a bit in this field is set
		its ColourValue is ignored. This is a combination of TVC_AMBIENT, TVC_DIFFUSE, TVC_SPECULAR(note that the shininess value is still
		taken from shininess) and TVC_EMISSIVE. TVC_NONE means that there will be no material property
		tracking the vertex colours.
		*/
		virtual void _setSurfaceParams(const ColourValue &ambient,
			const ColourValue &diffuse, const ColourValue &specular,
			const ColourValue &emissive, Real shininess,
			TrackVertexColourType tracking = TVC_NONE) = 0;

		/** Sets whether or not rendering points using OT_POINT_LIST will 
		render point sprites (textured quads) or plain points.
		@param enabled True enables point sprites, false returns to normal
		point rendering.
		*/	
		virtual void _setPointSpritesEnabled(bool enabled) = 0;

		/** Sets the size of points and how they are attenuated with distance.
		@remarks
		When performing point rendering or point sprite rendering,
		point size can be attenuated with distance. The equation for
		doing this is attenuation = 1 / (constant + linear * dist + quadratic * d^2) .
		@par
		For example, to disable distance attenuation (constant screensize) 
		you would set constant to 1, and linear and quadratic to 0. A
		standard perspective attenuation would be 0, 1, 0 respectively.
		*/
		virtual void _setPointParameters(Real size, bool attenuationEnabled, 
			Real constant, Real linear, Real quadratic, Real minSize, Real maxSize) = 0;


		/**
		Sets the texture to bind to a given texture unit.

		User processes would not normally call this direct unless rendering
		primitives themselves.

		@param unit The index of the texture unit to modify. Multitexturing 
		hardware can support multiple units (see 
		RenderSystemCapabilites::getNumTextureUnits)
		@param enabled Boolean to turn the unit on/off
		@param texPtr Pointer to the texture to use.
		*/
		virtual void _setTexture(size_t unit, bool enabled, 
			const TexturePtr &texPtr) = 0;
		/**
		Sets the texture to bind to a given texture unit.

		User processes would not normally call this direct unless rendering
		primitives themselves.

		@param unit The index of the texture unit to modify. Multitexturing 
		hardware can support multiple units (see 
		RenderSystemCapabilites::getNumTextureUnits)
		@param enabled Boolean to turn the unit on/off
		@param texname The name of the texture to use - this should have
		already been loaded with TextureManager::load.
		*/
		virtual void _setTexture(size_t unit, bool enabled, const String &texname);

		/** Binds a texture to a vertex sampler.
		@remarks
		Not all rendersystems support separate vertex samplers. For those that
		do, you can set a texture for them, separate to the regular texture
		samplers, using this method. For those that don't, you should use the
		regular texture samplers which are shared between the vertex and
		fragment units; calling this method will throw an exception.
		@see RenderSystemCapabilites::getVertexTextureUnitsShared
		*/
		virtual void _setVertexTexture(size_t unit, const TexturePtr& tex);

		/**
		Sets the texture coordinate set to use for a texture unit.

		Meant for use internally - not generally used directly by apps - the Material and TextureUnitState
		classes let you manage textures far more easily.

		@param unit Texture unit as above
		@param index The index of the texture coordinate set to use.
		*/
		virtual void _setTextureCoordSet(size_t unit, size_t index) = 0;

		/**
		Sets a method for automatically calculating texture coordinates for a stage.
		Should not be used by apps - for use by Ogre only.
		@param unit Texture unit as above
		@param m Calculation method to use
		@param frustum Optional Frustum param, only used for projective effects
		*/
		virtual void _setTextureCoordCalculation(size_t unit, TexCoordCalcMethod m, 
			const Frustum* frustum = 0) = 0;

		/** Sets the texture blend modes from a TextureUnitState record.
		Meant for use internally only - apps should use the Material
		and TextureUnitState classes.
		@param unit Texture unit as above
		@param bm Details of the blending mode
		*/
		virtual void _setTextureBlendMode(size_t unit, const LayerBlendModeEx& bm) = 0;

		/** Sets the filtering options for a given texture unit.
		@param unit The texture unit to set the filtering options for
		@param minFilter The filter used when a texture is reduced in size
		@param magFilter The filter used when a texture is magnified
		@param mipFilter The filter used between mipmap levels, FO_NONE disables mipmapping
		*/
		virtual void _setTextureUnitFiltering(size_t unit, FilterOptions minFilter,
			FilterOptions magFilter, FilterOptions mipFilter);

		/** Sets a single filter for a given texture unit.
		@param unit The texture unit to set the filtering options for
		@param ftype The filter type
		@param filter The filter to be used
		*/
		virtual void _setTextureUnitFiltering(size_t unit, FilterType ftype, FilterOptions filter) = 0;

		/** Sets the maximal anisotropy for the specified texture unit.*/
		virtual void _setTextureLayerAnisotropy(size_t unit, unsigned int maxAnisotropy) = 0;

		/** Sets the texture addressing mode for a texture unit.*/
		virtual void _setTextureAddressingMode(size_t unit, const TextureUnitState::UVWAddressingMode& uvw) = 0;

		/** Sets the texture border colour for a texture unit.*/
		virtual void _setTextureBorderColour(size_t unit, const ColourValue& colour) = 0;

		/** Sets the mipmap bias value for a given texture unit.
		@remarks
		This allows you to adjust the mipmap calculation up or down for a
		given texture unit. Negative values force a larger mipmap to be used, 
		positive values force a smaller mipmap to be used. Units are in numbers
		of levels, so +1 forces the mipmaps to one smaller level.
		@note Only does something if render system has capability RSC_MIPMAP_LOD_BIAS.
		*/
		virtual void _setTextureMipmapBias(size_t unit, float bias) = 0;

		/** Sets the texture coordinate transformation matrix for a texture unit.
		@param unit Texture unit to affect
		@param xform The 4x4 matrix
		*/
		virtual void _setTextureMatrix(size_t unit, const Matrix4& xform) = 0;

		/** Sets the global blending factors for combining subsequent renders with the existing frame contents.
		The result of the blending operation is:</p>
		<p align="center">final = (texture * sourceFactor) + (pixel * destFactor)</p>
		Each of the factors is specified as one of a number of options, as specified in the SceneBlendFactor
		enumerated type.
		By changing the operation you can change addition between the source and destination pixels to a different operator.
		@param sourceFactor The source factor in the above calculation, i.e. multiplied by the texture colour components.
		@param destFactor The destination factor in the above calculation, i.e. multiplied by the pixel colour components.
		@param op The blend operation mode for combining pixels
		*/
		virtual void _setSceneBlending(SceneBlendFactor sourceFactor, SceneBlendFactor destFactor, SceneBlendOperation op = SBO_ADD) = 0;

		/** Sets the global blending factors for combining subsequent renders with the existing frame contents.
		The result of the blending operation is:</p>
		<p align="center">final = (texture * sourceFactor) + (pixel * destFactor)</p>
		Each of the factors is specified as one of a number of options, as specified in the SceneBlendFactor
		enumerated type.
		@param sourceFactor The source factor in the above calculation, i.e. multiplied by the texture colour components.
		@param destFactor The destination factor in the above calculation, i.e. multiplied by the pixel colour components.
		@param sourceFactorAlpha The source factor in the above calculation for the alpha channel, i.e. multiplied by the texture alpha components.
		@param destFactorAlpha The destination factor in the above calculation for the alpha channel, i.e. multiplied by the pixel alpha components.
		@param op The blend operation mode for combining pixels
		@param alphaOp The blend operation mode for combining pixel alpha values
		*/
		virtual void _setSeparateSceneBlending(SceneBlendFactor sourceFactor, SceneBlendFactor destFactor, SceneBlendFactor sourceFactorAlpha, 
			SceneBlendFactor destFactorAlpha, SceneBlendOperation op = SBO_ADD, SceneBlendOperation alphaOp = SBO_ADD) = 0;

		/** Sets the global alpha rejection approach for future renders.
		By default images are rendered regardless of texture alpha. This method lets you change that.
		@param func The comparison function which must pass for a pixel to be written.
		@param val The value to compare each pixels alpha value to (0-255)
		@param alphaToCoverage Whether to enable alpha to coverage, if supported
		*/
		virtual void _setAlphaRejectSettings(CompareFunction func, unsigned char value, bool alphaToCoverage) = 0;

		/** Notify the rendersystem that it should adjust texture projection to be 
			relative to a different origin.
		*/
		virtual void _setTextureProjectionRelativeTo(bool enabled, const Vector3& pos);
		/**
		* Signifies the beginning of a frame, i.e. the start of rendering on a single viewport. Will occur
		* several times per complete frame if multiple viewports exist.
		*/
		virtual void _beginFrame(void) = 0;
		
		//Dummy structure for render system contexts - implementing RenderSystems can extend
		//as needed
		struct RenderSystemContext { };
		/**
		* Pause rendering for a frame. This has to be called after _beginFrame and before _endFrame.
		* Will usually be called by the SceneManager, don't use this manually unless you know what
		* you are doing.
		*/
		virtual RenderSystemContext* _pauseFrame(void);
		/**
		* Resume rendering for a frame. This has to be called after a _pauseFrame call
		* Will usually be called by the SceneManager, don't use this manually unless you know what
		* you are doing.
		* @param context the render system context, as returned by _pauseFrame
		*/
		virtual void _resumeFrame(RenderSystemContext* context);

		/**
		* Ends rendering of a frame to the current viewport.
		*/
		virtual void _endFrame(void) = 0;
		/**
		Sets the provided viewport as the active one for future
		rendering operations. This viewport is aware of it's own
		camera and render target. Must be implemented by subclass.

		@param target Pointer to the appropriate viewport.
		*/
		virtual void _setViewport(Viewport *vp) = 0;
		/** Get the current active viewport for rendering. */
		virtual Viewport* _getViewport(void);

		/** Sets the culling mode for the render system based on the 'vertex winding'.
		A typical way for the rendering engine to cull triangles is based on the
		'vertex winding' of triangles. Vertex winding refers to the direction in
		which the vertices are passed or indexed to in the rendering operation as viewed
		from the camera, and will wither be clockwise or anticlockwise (that's 'counterclockwise' for
		you Americans out there ;) The default is CULL_CLOCKWISE i.e. that only triangles whose vertices
		are passed/indexed in anticlockwise order are rendered - this is a common approach and is used in 3D studio models
		for example. You can alter this culling mode if you wish but it is not advised unless you know what you are doing.
		You may wish to use the CULL_NONE option for mesh data that you cull yourself where the vertex
		winding is uncertain.
		*/
		virtual void _setCullingMode(CullingMode mode) = 0;

		virtual CullingMode _getCullingMode(void) const;

		/** Sets the mode of operation for depth buffer tests from this point onwards.
		Sometimes you may wish to alter the behaviour of the depth buffer to achieve
		special effects. Because it's unlikely that you'll set these options for an entire frame,
		but rather use them to tweak settings between rendering objects, this is an internal
		method (indicated by the '_' prefix) which will be used by a SceneManager implementation
		rather than directly from the client application.
		If this method is never called the settings are automatically the same as the default parameters.
		@param depthTest If true, the depth buffer is tested for each pixel and the frame buffer is only updated
		if the depth function test succeeds. If false, no test is performed and pixels are always written.
		@param depthWrite If true, the depth buffer is updated with the depth of the new pixel if the depth test succeeds.
		If false, the depth buffer is left unchanged even if a new pixel is written.
		@param depthFunction Sets the function required for the depth test.
		*/
		virtual void _setDepthBufferParams(bool depthTest = true, bool depthWrite = true, CompareFunction depthFunction = CMPF_LESS_EQUAL) = 0;

		/** Sets whether or not the depth buffer check is performed before a pixel write.
		@param enabled If true, the depth buffer is tested for each pixel and the frame buffer is only updated
		if the depth function test succeeds. If false, no test is performed and pixels are always written.
		*/
		virtual void _setDepthBufferCheckEnabled(bool enabled = true) = 0;
		/** Sets whether or not the depth buffer is updated after a pixel write.
		@param enabled If true, the depth buffer is updated with the depth of the new pixel if the depth test succeeds.
		If false, the depth buffer is left unchanged even if a new pixel is written.
		*/
		virtual void _setDepthBufferWriteEnabled(bool enabled = true) = 0;
		/** Sets the comparison function for the depth buffer check.
		Advanced use only - allows you to choose the function applied to compare the depth values of
		new and existing pixels in the depth buffer. Only an issue if the deoth buffer check is enabled
		(see _setDepthBufferCheckEnabled)
		@param  func The comparison between the new depth and the existing depth which must return true
		for the new pixel to be written.
		*/
		virtual void _setDepthBufferFunction(CompareFunction func = CMPF_LESS_EQUAL) = 0;
		/** Sets whether or not colour buffer writing is enabled, and for which channels. 
		@remarks
		For some advanced effects, you may wish to turn off the writing of certain colour
		channels, or even all of the colour channels so that only the depth buffer is updated
		in a rendering pass. However, the chances are that you really want to use this option
		through the Material class.
		@param red, green, blue, alpha Whether writing is enabled for each of the 4 colour channels. */
		virtual void _setColourBufferWriteEnabled(bool red, bool green, bool blue, bool alpha) = 0;
		/** Sets the depth bias, NB you should use the Material version of this. 
		@remarks
		When polygons are coplanar, you can get problems with 'depth fighting' where
		the pixels from the two polys compete for the same screen pixel. This is particularly
		a problem for decals (polys attached to another surface to represent details such as
		bulletholes etc.).
		@par
		A way to combat this problem is to use a depth bias to adjust the depth buffer value
		used for the decal such that it is slightly higher than the true value, ensuring that
		the decal appears on top.
		@note
		The final bias value is a combination of a constant bias and a bias proportional
		to the maximum depth slope of the polygon being rendered. The final bias
		is constantBias + slopeScaleBias * maxslope. Slope scale biasing is
		generally preferable but is not available on older hardware.
		@param constantBias The constant bias value, expressed as a value in 
		homogeneous depth coordinates.
		@param slopeScaleBias The bias value which is factored by the maximum slope
		of the polygon, see the description above. This is not supported by all
		cards.

		*/
		virtual void _setDepthBias(float constantBias, float slopeScaleBias = 0.0f) = 0;
		/** Sets the fogging mode for future geometry.
		@param mode Set up the mode of fog as described in the FogMode enum, or set to FOG_NONE to turn off.
		@param colour The colour of the fog. Either set this to the same as your viewport background colour,
		or to blend in with a skydome or skybox.
		@param expDensity The density of the fog in FOG_EXP or FOG_EXP2 mode, as a value between 0 and 1. The default is 1. i.e. completely opaque, lower values can mean
		that fog never completely obscures the scene.
		@param linearStart Distance at which linear fog starts to encroach. The distance must be passed
		as a parametric value between 0 and 1, with 0 being the near clipping plane, and 1 being the far clipping plane. Only applicable if mode is FOG_LINEAR.
		@param linearEnd Distance at which linear fog becomes completely opaque.The distance must be passed
		as a parametric value between 0 and 1, with 0 being the near clipping plane, and 1 being the far clipping plane. Only applicable if mode is FOG_LINEAR.
		*/
		virtual void _setFog(FogMode mode = FOG_NONE, const ColourValue& colour = ColourValue::White, Real expDensity = 1.0, Real linearStart = 0.0, Real linearEnd = 1.0) = 0;


		/** The RenderSystem will keep a count of tris rendered, this resets the count. */
		virtual void _beginGeometryCount(void);
		/** Reports the number of tris rendered since the last _beginGeometryCount call. */
		virtual unsigned int _getFaceCount(void) const;
		/** Reports the number of batches rendered since the last _beginGeometryCount call. */
		virtual unsigned int _getBatchCount(void) const;
		/** Reports the number of vertices passed to the renderer since the last _beginGeometryCount call. */
		virtual unsigned int _getVertexCount(void) const;

		/** Generates a packed data version of the passed in ColourValue suitable for
		use as with this RenderSystem.
		@remarks
		Since different render systems have different colour data formats (eg
		RGBA for GL, ARGB for D3D) this method allows you to use 1 method for all.
		@param colour The colour to convert
		@param pDest Pointer to location to put the result.
		*/
		virtual void convertColourValue(const ColourValue& colour, uint32* pDest);
		/** Get the native VertexElementType for a compact 32-bit colour value
		for this rendersystem.
		*/
		virtual VertexElementType getColourVertexElementType(void) const = 0;

		/** Converts a uniform projection matrix to suitable for this render system.
		@remarks
		Because different APIs have different requirements (some incompatible) for the
		projection matrix, this method allows each to implement their own correctly and pass
		back a generic OGRE matrix for storage in the engine.
		*/
		virtual void _convertProjectionMatrix(const Matrix4& matrix,
			Matrix4& dest, bool forGpuProgram = false) = 0;

		/** Builds a perspective projection matrix suitable for this render system.
		@remarks
		Because different APIs have different requirements (some incompatible) for the
		projection matrix, this method allows each to implement their own correctly and pass
		back a generic OGRE matrix for storage in the engine.
		*/
		virtual void _makeProjectionMatrix(const Radian& fovy, Real aspect, Real nearPlane, Real farPlane, 
			Matrix4& dest, bool forGpuProgram = false) = 0;

		/** Builds a perspective projection matrix for the case when frustum is
		not centered around camera.
		@remarks
		Viewport coordinates are in camera coordinate frame, i.e. camera is 
		at the origin.
		*/
		virtual void _makeProjectionMatrix(Real left, Real right, Real bottom, Real top, 
			Real nearPlane, Real farPlane, Matrix4& dest, bool forGpuProgram = false) = 0;
		/** Builds an orthographic projection matrix suitable for this render system.
		@remarks
		Because different APIs have different requirements (some incompatible) for the
		projection matrix, this method allows each to implement their own correctly and pass
		back a generic OGRE matrix for storage in the engine.
		*/
		virtual void _makeOrthoMatrix(const Radian& fovy, Real aspect, Real nearPlane, Real farPlane, 
			Matrix4& dest, bool forGpuProgram = false) = 0;

		/** Update a perspective projection matrix to use 'oblique depth projection'.
		@remarks
		This method can be used to change the nature of a perspective 
		transform in order to make the near plane not perpendicular to the 
		camera view direction, but to be at some different orientation. 
		This can be useful for performing arbitrary clipping (e.g. to a 
		reflection plane) which could otherwise only be done using user
		clip planes, which are more expensive, and not necessarily supported
		on all cards.
		@param matrix The existing projection matrix. Note that this must be a
		perspective transform (not orthographic), and must not have already
		been altered by this method. The matrix will be altered in-place.
		@param plane The plane which is to be used as the clipping plane. This
		plane must be in CAMERA (view) space.
		@param forGpuProgram Is this for use with a Gpu program or fixed-function
		*/
		virtual void _applyObliqueDepthProjection(Matrix4& matrix, const Plane& plane, 
			bool forGpuProgram) = 0;

		/** Sets how to rasterise triangles, as points, wireframe or solid polys. */
		virtual void _setPolygonMode(PolygonMode level) = 0;

		/** Turns stencil buffer checking on or off. 
		@remarks
		Stencilling (masking off areas of the rendering target based on the stencil 
		buffer) can be turned on or off using this method. By default, stencilling is
		disabled.
		*/
		virtual void setStencilCheckEnabled(bool enabled) = 0;
		/** Determines if this system supports hardware accelerated stencil buffer. 
		@remarks
		Note that the lack of this function doesn't mean you can't do stencilling, but
		the stencilling operations will be provided in software, which will NOT be
		fast.
		@par
		Generally hardware stencils are only supported in 32-bit colour modes, because
		the stencil buffer shares the memory of the z-buffer, and in most cards the 
		z-buffer has to be the same depth as the colour buffer. This means that in 32-bit
		mode, 24 bits of the z-buffer are depth and 8 bits are stencil. In 16-bit mode there
		is no room for a stencil (although some cards support a 15:1 depth:stencil option,
		this isn't useful for very much) so 8 bits of stencil are provided in software.
		This can mean that if you use stencilling, your applications may be faster in 
		32-but colour than in 16-bit, which may seem odd to some people.
		*/
		/*virtual bool hasHardwareStencil(void) = 0;*/

		/** This method allows you to set all the stencil buffer parameters in one call.
		@remarks
		The stencil buffer is used to mask out pixels in the render target, allowing
		you to do effects like mirrors, cut-outs, stencil shadows and more. Each of
		your batches of rendering is likely to ignore the stencil buffer, 
		update it with new values, or apply it to mask the output of the render.
		The stencil test is:<PRE>
		(Reference Value & Mask) CompareFunction (Stencil Buffer Value & Mask)</PRE>
		The result of this will cause one of 3 actions depending on whether the test fails,
		succeeds but with the depth buffer check still failing, or succeeds with the
		depth buffer check passing too.
		@par
		Unlike other render states, stencilling is left for the application to turn
		on and off when it requires. This is because you are likely to want to change
		parameters between batches of arbitrary objects and control the ordering yourself.
		In order to batch things this way, you'll want to use OGRE's separate render queue
		groups (see RenderQueue) and register a RenderQueueListener to get notifications
		between batches.
		@par
		There are individual state change methods for each of the parameters set using 
		this method. 
		Note that the default values in this method represent the defaults at system 
		start up too.
		@param func The comparison function applied.
		@param refValue The reference value used in the comparison
		@param mask The bitmask applied to both the stencil value and the reference value 
		before comparison
		@param stencilFailOp The action to perform when the stencil check fails
		@param depthFailOp The action to perform when the stencil check passes, but the
		depth buffer check still fails
		@param passOp The action to take when both the stencil and depth check pass.
		@param twoSidedOperation If set to true, then if you render both back and front faces 
		(you'll have to turn off culling) then these parameters will apply for front faces, 
		and the inverse of them will happen for back faces (keep remains the same).
		*/
		virtual void setStencilBufferParams(CompareFunction func = CMPF_ALWAYS_PASS, 
			uint32 refValue = 0, uint32 mask = 0xFFFFFFFF, 
			StencilOperation stencilFailOp = SOP_KEEP, 
			StencilOperation depthFailOp = SOP_KEEP,
			StencilOperation passOp = SOP_KEEP, 
			bool twoSidedOperation = false) = 0;



		/** Sets the current vertex declaration, ie the source of vertex data. */
		virtual void setVertexDeclaration(VertexDeclaration* decl) = 0;
		/** Sets the current vertex buffer binding state. */
		virtual void setVertexBufferBinding(VertexBufferBinding* binding) = 0;

		/** Sets whether or not normals are to be automatically normalised.
		@remarks
		This is useful when, for example, you are scaling SceneNodes such that
		normals may not be unit-length anymore. Note though that this has an
		overhead so should not be turn on unless you really need it.
		@par
		You should not normally call this direct unless you are rendering
		world geometry; set it on the Renderable because otherwise it will be
		overridden by material settings. 
		*/
		virtual void setNormaliseNormals(bool normalise) = 0;

		/**
		Render something to the active viewport.

		Low-level rendering interface to perform rendering
		operations. Unlikely to be used directly by client
		applications, since the SceneManager and various support
		classes will be responsible for calling this method.
		Can only be called between _beginScene and _endScene

		@param op A rendering operation instance, which contains
		details of the operation to be performed.
		*/
		virtual void _render(const RenderOperation& op);

		/** Gets the capabilities of the render system. */
		const RenderSystemCapabilities* getCapabilities(void) const { return mCurrentCapabilities; }


		/** Returns the driver version.
		*/
		virtual const DriverVersion& getDriverVersion(void) const { return mDriverVersion; }

		/** Binds a given GpuProgram (but not the parameters). 
		@remarks Only one GpuProgram of each type can be bound at once, binding another
		one will simply replace the existing one.
		*/
		virtual void bindGpuProgram(GpuProgram* prg);

		/** Bind Gpu program parameters.
		@param gptype The type of program to bind the parameters to
		@param params The parameters to bind
		@param variabilityMask A mask of GpuParamVariability identifying which params need binding
		*/
		virtual void bindGpuProgramParameters(GpuProgramType gptype, 
			GpuProgramParametersSharedPtr params, uint16 variabilityMask) = 0;

		/** Only binds Gpu program parameters used for passes that have more than one iteration rendering
		*/
		virtual void bindGpuProgramPassIterationParameters(GpuProgramType gptype) = 0;
		/** Unbinds GpuPrograms of a given GpuProgramType.
		@remarks
		This returns the pipeline to fixed-function processing for this type.
		*/
		virtual void unbindGpuProgram(GpuProgramType gptype);

		/** Returns whether or not a Gpu program of the given type is currently bound. */
		virtual bool isGpuProgramBound(GpuProgramType gptype);

		/** Sets the user clipping region.
		*/
		virtual void setClipPlanes(const PlaneList& clipPlanes);

		/** Add a user clipping plane. */
		virtual void addClipPlane (const Plane &p);
		/** Add a user clipping plane. */
		virtual void addClipPlane (Real A, Real B, Real C, Real D);

		/** Clears the user clipping region.
		*/
		virtual void resetClipPlanes();

		/** Utility method for initialising all render targets attached to this rendering system. */
		virtual void _initRenderTargets(void);

		/** Utility method to notify all render targets that a camera has been removed, 
		in case they were referring to it as their viewer. 
		*/
		virtual void _notifyCameraRemoved(const Camera* cam);

		/** Internal method for updating all render targets attached to this rendering system. */
		virtual void _updateAllRenderTargets(bool swapBuffers = true);
		/** Internal method for swapping all the buffers on all render targets,
		if _updateAllRenderTargets was called with a 'false' parameter. */
		virtual void _swapAllRenderTargetBuffers(bool waitForVsync = true);

		/** Gets whether or not vertex windings set should be inverted; this can be important
		for rendering reflections. */
		virtual bool getInvertVertexWinding(void);

		/** Sets whether or not vertex windings set should be inverted; this can be important
		for rendering reflections. */
		virtual void setInvertVertexWinding(bool invert);

		/** Indicates whether or not the vertex windings set will be inverted for the current render (e.g. reflections)
		@see RenderSystem::setInvertVertexWinding
		*/
		virtual bool getVertexWindingInverted(void) const;

		/** Sets the 'scissor region' ie the region of the target in which rendering can take place.
		@remarks
		This method allows you to 'mask off' rendering in all but a given rectangular area
		as identified by the parameters to this method.
		@note
		Not all systems support this method. Check the RenderSystemCapabilities for the
		RSC_SCISSOR_TEST capability to see if it is supported.
		@param enabled True to enable the scissor test, false to disable it.
		@param left, top, right, bottom The location of the corners of the rectangle, expressed in
		<i>pixels</i>.
		*/
		virtual void setScissorTest(bool enabled, size_t left = 0, size_t top = 0, 
			size_t right = 800, size_t bottom = 600) = 0;

		/** Clears one or more frame buffers on the active render target. 
		@param buffers Combination of one or more elements of FrameBufferType
		denoting which buffers are to be cleared
		@param colour The colour to clear the colour buffer with, if enabled
		@param depth The value to initialise the depth buffer with, if enabled
		@param stencil The value to initialise the stencil buffer with, if enabled.
		*/
		virtual void clearFrameBuffer(unsigned int buffers, 
			const ColourValue& colour = ColourValue::Black, 
			Real depth = 1.0f, unsigned short stencil = 0) = 0;
		/** Returns the horizontal texel offset value required for mapping 
		texel origins to pixel origins in this rendersystem.
		@remarks
		Since rendersystems sometimes disagree on the origin of a texel, 
		mapping from texels to pixels can sometimes be problematic to 
		implement generically. This method allows you to retrieve the offset
		required to map the origin of a texel to the origin of a pixel in
		the horizontal direction.
		*/
		virtual Real getHorizontalTexelOffset(void) = 0;
		/** Returns the vertical texel offset value required for mapping 
		texel origins to pixel origins in this rendersystem.
		@remarks
		Since rendersystems sometimes disagree on the origin of a texel, 
		mapping from texels to pixels can sometimes be problematic to 
		implement generically. This method allows you to retrieve the offset
		required to map the origin of a texel to the origin of a pixel in
		the vertical direction.
		*/
		virtual Real getVerticalTexelOffset(void) = 0;

		/** Gets the minimum (closest) depth value to be used when rendering
		using identity transforms.
		@remarks
		When using identity transforms you can manually set the depth
		of a vertex; however the input values required differ per
		rendersystem. This method lets you retrieve the correct value.
		@see Renderable::getUseIdentityView, Renderable::getUseIdentityProjection
		*/
		virtual Real getMinimumDepthInputValue(void) = 0;
		/** Gets the maximum (farthest) depth value to be used when rendering
		using identity transforms.
		@remarks
		When using identity transforms you can manually set the depth
		of a vertex; however the input values required differ per
		rendersystem. This method lets you retrieve the correct value.
		@see Renderable::getUseIdentityView, Renderable::getUseIdentityProjection
		*/
		virtual Real getMaximumDepthInputValue(void) = 0;
		/** set the current multi pass count value.  This must be set prior to 
		calling _render() if multiple renderings of the same pass state are 
		required.
		@param count Number of times to render the current state.
		*/
		virtual void setCurrentPassIterationCount(const size_t count) { mCurrentPassIterationCount = count; }

		/** Tell the render system whether to derive a depth bias on its own based on 
		the values passed to it in setCurrentPassIterationCount.
		The depth bias set will be baseValue + iteration * multiplier
		@param derive True to tell the RS to derive this automatically
		@param baseValue The base value to which the multiplier should be
		added
		@param multiplier The amount of depth bias to apply per iteration
		@param slopeScale The constant slope scale bias for completeness
		*/
		virtual void setDeriveDepthBias(bool derive, float baseValue = 0.0f,
			float multiplier = 0.0f, float slopeScale = 0.0f)
		{
			mDerivedDepthBias = derive;
			mDerivedDepthBiasBase = baseValue;
			mDerivedDepthBiasMultiplier = multiplier;
			mDerivedDepthBiasSlopeScale = slopeScale;
		}

		/**
         * Set current render target to target, enabling its device context if needed
         */
        virtual void _setRenderTarget(RenderTarget *target) = 0;

		/** Defines a listener on the custom events that this render system 
		can raise.
		@see RenderSystem::addListener
		*/
		class _OgreExport Listener
		{
		public:
			Listener() {}
			virtual ~Listener() {}

			/** A rendersystem-specific event occurred.
			@param eventName The name of the event which has occurred
			@param parameters A list of parameters that may belong to this event,
			may be null if there are no parameters
			*/
			virtual void eventOccurred(const String& eventName, 
				const NameValuePairList* parameters = 0) = 0;
		};
		/** Adds a listener to the custom events that this render system can raise.
		@remarks
		Some render systems have quite specific, internally generated events 
		that the application may wish to be notified of. Many applications
		don't have to worry about these events, and can just trust OGRE to 
		handle them, but if you want to know, you can add a listener here.
		@par
		Events are raised very generically by string name. Perhaps the most 
		common example of a render system specific event is the loss and 
		restoration of a device in DirectX; which OGRE deals with, but you 
		may wish to know when it happens. 
		@see RenderSystem::getRenderSystemEvents
		*/
		virtual void addListener(Listener* l);
		/** Remove a listener to the custom events that this render system can raise.
		*/
		virtual void removeListener(Listener* l);

		/** Gets a list of the rendersystem specific events that this rendersystem
		can raise.
		@see RenderSystem::addListener
		*/
		virtual const StringVector& getRenderSystemEvents(void) const { return mEventNames; }

		/** Tell the rendersystem to perform any prep tasks it needs to directly
		before other threads which might access the rendering API are registered.
		@remarks
		Call this from your main thread before starting your other threads
		(which themselves should call registerThread()). Note that if you
		start your own threads, there is a specific startup sequence which 
		must be respected and requires synchronisation between the threads:
		<ol>
		<li>[Main thread]Call preExtraThreadsStarted</li>
		<li>[Main thread]Start other thread, wait</li>
		<li>[Other thread]Call registerThread, notify main thread & continue</li>
		<li>[Main thread]Wake up & call postExtraThreadsStarted</li>
		</ol>
		Once this init sequence is completed the threads are independent but
		this startup sequence must be respected.
		*/
		virtual void preExtraThreadsStarted() = 0;

		/* Tell the rendersystem to perform any tasks it needs to directly
		after other threads which might access the rendering API are registered.
		@see RenderSystem::preExtraThreadsStarted
		*/
		virtual void postExtraThreadsStarted() = 0;

		/** Register the an additional thread which may make calls to rendersystem-related 
		objects.
		@remarks
		This method should only be called by additional threads during their
		initialisation. If they intend to use hardware rendering system resources 
		they should call this method before doing anything related to the render system.
		Some rendering APIs require a per-thread setup and this method will sort that
		out. It is also necessary to call unregisterThread before the thread shuts down.
		@note
		This method takes no parameters - it must be called from the thread being
		registered and that context is enough.
		*/
		virtual void registerThread() = 0;

		/** Unregister an additional thread which may make calls to rendersystem-related objects.
		@see RenderSystem::registerThread
		*/
		virtual void unregisterThread() = 0;

		/**
		* Gets the number of display monitors.
		@see Root::getDisplayMonitorCount
		*/
		virtual unsigned int getDisplayMonitorCount() const = 0;
	protected:


		/** The render targets. */
		RenderTargetMap mRenderTargets;
		/** The render targets, ordered by priority. */
		RenderTargetPriorityMap mPrioritisedRenderTargets;
		/** The Active render target. */
		RenderTarget * mActiveRenderTarget;
		/** The Active GPU programs and gpu program parameters*/
		GpuProgramParametersSharedPtr mActiveVertexGpuProgramParameters;
		GpuProgramParametersSharedPtr mActiveGeometryGpuProgramParameters;
		GpuProgramParametersSharedPtr mActiveFragmentGpuProgramParameters;

		// Texture manager
		// A concrete class of this will be created and
		// made available under the TextureManager singleton,
		// managed by the RenderSystem
		TextureManager* mTextureManager;

		// Active viewport (dest for future rendering operations)
		Viewport* mActiveViewport;

		CullingMode mCullingMode;

		bool mVSync;
		unsigned int mVSyncInterval;
		bool mWBuffer;

		size_t mBatchCount;
		size_t mFaceCount;
		size_t mVertexCount;

		/// Saved manual colour blends
		ColourValue mManualBlendColours[OGRE_MAX_TEXTURE_LAYERS][2];

		bool mInvertVertexWinding;

		/// Texture units from this upwards are disabled
		size_t mDisabledTexUnitsFrom;

		/// number of times to render the current state
		size_t mCurrentPassIterationCount;
		size_t mCurrentPassIterationNum;
		/// Whether to update the depth bias per render call
		bool mDerivedDepthBias;
		float mDerivedDepthBiasBase;
		float mDerivedDepthBiasMultiplier;
		float mDerivedDepthBiasSlopeScale;

		/** updates pass iteration rendering state including bound gpu program parameter
		pass iteration auto constant entry
		@returns True if more iterations are required
		*/
		bool updatePassIterationRenderState(void);

		/// List of names of events this rendersystem may raise
		StringVector mEventNames;

		/// Internal method for firing a rendersystem event
		virtual void fireEvent(const String& name, const NameValuePairList* params = 0);

		typedef list<Listener*>::type ListenerList;
		ListenerList mEventListeners;

		typedef list<HardwareOcclusionQuery*>::type HardwareOcclusionQueryList;
		HardwareOcclusionQueryList mHwOcclusionQueries;

		bool mVertexProgramBound;
		bool mGeometryProgramBound;
		bool mFragmentProgramBound;

		// Recording user clip planes
		PlaneList mClipPlanes;
		// Indicator that we need to re-set the clip planes on next render call
		bool mClipPlanesDirty;

		/// Used to store the capabilities of the graphics card
		RenderSystemCapabilities* mRealCapabilities;
		RenderSystemCapabilities* mCurrentCapabilities;
		bool mUseCustomCapabilities;

		/// Internal method used to set the underlying clip planes when needed
		virtual void setClipPlanesImpl(const PlaneList& clipPlanes) = 0;

		/** Initialize the render system from the capabilities*/
		virtual void initialiseFromRenderSystemCapabilities(RenderSystemCapabilities* caps, RenderTarget* primary) = 0;


		DriverVersion mDriverVersion;

		bool mTexProjRelative;
		Vector3 mTexProjRelativeOrigin;



	};
	/** @} */
	/** @} */
}

#endif
