source: trunk/VUT/work/ogre_changes/RenderSystems/GL/include/OgreGLHardwareOcclusionQuery.h @ 88

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

Copyright (c) 2000-2005 The OGRE Team
Also see acknowledgements in Readme.html

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later
version.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with
this program; if not, write to the Free Software Foundation, Inc., 59 Temple
Place - Suite 330, Boston, MA 02111-1307, USA, or go to
http://www.gnu.org/copyleft/lesser.txt.
-----------------------------------------------------------------------------
*/

/*
The nVidia occlusion query extension is defined in glext.h so you don't 
need anything else. You do need to look up the function, we provide a 
GLSupport class to do this, which has platform implementations for 
getProcAddress. Check the way that extensions like glActiveTextureARB are 
initialised and used in glRenderSystem and copy what is done there.



  To do: fix so dx7 and DX9 checks and flags if HW Occlusion is supported
  See the openGl dito for ideas what to do.

*/



//GL_ActiveTextureARB_Func* glActiveTextureARB_ptr = (GL_ActiveTextureARB_Func)mGLSupport->getProcAddress("glActiveTextureARB");

#ifndef __GLHARDWAREOCCLUSIONQUERY_H__
#define __GLHARDWAREOCCLUSIONQUERY_H__

#include "OgreGLPrerequisites.h"
#include "OgreHardwareOcclusionQuery.h"


namespace Ogre { 


// If you use multiple rendering passes you can test only the first pass and all other passes don't have to be rendered 
// if the first pass resultet has too few pixels visable.

// Be sure to render all occlluder first and whats out so the RenderQue don't switch places on 
// the occluding objects and the tested objects because it thinks it's more effective..


/**
  * This is a class that is the base class of the query class for 
  * hardware occlusion.
  *
  * @author Lee Sandberg email: lee@abcmedia.se
  */

class GLHardwareOcclusionQuery : public HardwareOcclusionQuery
{
//----------------------------------------------------------------------
// Public methods
//--
public:
        /**
          * Default object constructor
          * 
          */
        GLHardwareOcclusionQuery();
        /**
          * Object destructor
          */
        ~GLHardwareOcclusionQuery();

        //------------------------------------------------------------------
        // Occlusion query functions (see base class documentation for this)
        //--

        void beginOcclusionQuery();
        void endOcclusionQuery();
        bool pullOcclusionQuery( unsigned int* NumOfFragments, const bool waitForResult );
        bool pullOcclusionQuery( unsigned int* NumOfFragments, const bool waitForResult,
                                                         const HW_OCCLUSIONQUERY flag  ); 

        unsigned int getLastQuerysPixelcount() { return m_uintPixelCount; }

        // This functions are optional, it's a simple filter that simply skipps some hardware occlusion tests on visable objects only
        // It's easy to use if you don't have to keep track on which objects are visable (can be skipped) and what objects arn't visable..
        // (None visable objects and object you introduce for the first time have allways to be tested allthough the cheepest possible 
        // LOD (Level Of Detail) mesh and material wize). 

        /**
          *   
          * Remarks This function allows you to set how often the hardware occlusion really sent to the driver
          * if you set it to 0 every hw occlusion test is acctually made. If you set it to 2 only 50% of your queries are sent. 
          * for all visable objects. 3 will result in 33% of all queries to acctualy be sent and so on. 
          * New and none visable objects will be tested all the time.
          * This functionality is here because this class can keep track on visable and none visable objects for you.
          * Once you you set the SkipRate for any hardware occlusion instance it effects all others.
          */

        void setSkipRate( int skip ) { m_Skip = skip; }         // Using 2 only 50 % of the tests are actully made and 3 results in only 33% of the tests. So on.
        int      getSkipRate() { return m_Skip; } 


//----------------------------------------------------------------------
// Protected members
//--
protected:

        unsigned int    m_uintPixelCount;
        unsigned int    m_uintQuery[1];
        bool                    m_bOcclusionQuery;
        int                             m_SkipCounter;          // m_SkipConter =  m_SkipConter % m_Skip; if ( m_SkipConter == 0 && m_uintPixelCount !=0 ) TestHWOcclusion else just return 
        static int              m_Skip;                         // This is shared by all instancies
        bool                    m_bHWOcclusionSupport;
};


}

#endif