/** 
 * @file llvowlsky.h
 * @brief LLVOWLSky class definition
 *
 * $LicenseInfo:firstyear=2007&license=viewergpl$
 * 
 * Copyright (c) 2007-2009, Linden Research, Inc.
 * 
 * Second Life Viewer Source Code
 * The source code in this file ("Source Code") is provided by Linden Lab
 * to you under the terms of the GNU General Public License, version 2.0
 * ("GPL"), unless you have obtained a separate licensing agreement
 * ("Other License"), formally executed by you and Linden Lab.  Terms of
 * the GPL can be found in doc/GPL-license.txt in this distribution, or
 * online at http://secondlifegrid.net/programs/open_source/licensing/gplv2
 * 
 * There are special exceptions to the terms and conditions of the GPL as
 * it is applied to this Source Code. View the full text of the exception
 * in the file doc/FLOSS-exception.txt in this software distribution, or
 * online at
 * http://secondlifegrid.net/programs/open_source/licensing/flossexception
 * 
 * By copying, modifying or distributing this software, you acknowledge
 * that you have read and understood your obligations described above,
 * and agree to abide by those obligations.
 * 
 * ALL LINDEN LAB SOURCE CODE IS PROVIDED "AS IS." LINDEN LAB MAKES NO
 * WARRANTIES, EXPRESS, IMPLIED OR OTHERWISE, REGARDING ITS ACCURACY,
 * COMPLETENESS OR PERFORMANCE.
 * $/LicenseInfo$
 */

#ifndef LL_VOWLSKY_H
#define LL_VOWLSKY_H

#include "llviewerobject.h"

class LLVOWLSky : public LLStaticViewerObject {
private:
	static const F32 DISTANCE_TO_STARS;

	// anything less than 3 makes it impossible to create a closed dome.
	static const U32 MIN_SKY_DETAIL;
	// anything bigger than about 180 will cause getStripsNumVerts() to exceed 65535.
	static const U32 MAX_SKY_DETAIL;

	inline static U32 getNumStacks(void);
	inline static U32 getNumSlices(void);
	inline static U32 getFanNumVerts(void);
	inline static U32 getFanNumIndices(void);
	inline static U32 getStripsNumVerts(void);
	inline static U32 getStripsNumIndices(void);
	inline static U32 getStarsNumVerts(void);
	inline static U32 getStarsNumIndices(void);

public:
	LLVOWLSky(const LLUUID &id, const LLPCode pcode, LLViewerRegion *regionp);

	void initSunDirection(LLVector3 const & sun_direction,
		LLVector3 const & sun_angular_velocity);

	/*virtual*/ BOOL		 idleUpdate(LLAgent &agent, LLWorld &world, const F64 &time);
	/*virtual*/ BOOL		 isActive(void) const;
	/*virtual*/ LLDrawable * createDrawable(LLPipeline *pipeline);
	/*virtual*/ BOOL		 updateGeometry(LLDrawable *drawable);

	void drawStars(void);
	void drawDome(void);
	void resetVertexBuffers(void);
	
	void cleanupGL();
	void restoreGL();

private:
	// a tiny helper function for controlling the sky dome tesselation.
	static F32 calcPhi(U32 i);

	// helper function for initializing the stars.
	void initStars();

	// helper function for building the fan vertex buffer.
	static void buildFanBuffer(LLStrider<LLVector3> & vertices,
							   LLStrider<LLVector2> & texCoords,
							   LLStrider<U16> & indices);

	// helper function for building the strips vertex buffer.
	// note begin_stack and end_stack follow stl iterator conventions,
	// begin_stack is the first stack to be included, end_stack is the first
	// stack not to be included.
	static void buildStripsBuffer(U32 begin_stack, U32 end_stack,
								  LLStrider<LLVector3> & vertices,
								  LLStrider<LLVector2> & texCoords,
								  LLStrider<U16> & indices);

	// helper function for updating the stars colors.
	void updateStarColors();

	// helper function for updating the stars geometry.
	BOOL updateStarGeometry(LLDrawable *drawable);

private:
	LLPointer<LLVertexBuffer>					mFanVerts;
	std::vector< LLPointer<LLVertexBuffer> >	mStripsVerts;
	LLPointer<LLVertexBuffer>					mStarsVerts;

	std::vector<LLVector3>	mStarVertices;				// Star verticies
	std::vector<LLColor4>	mStarColors;				// Star colors
	std::vector<F32>		mStarIntensities;			// Star intensities
};

#endif // LL_VOWLSKY_H
