source: GTP/trunk/App/Demos/Geom/OgreStuff/include/OgreHardwareOcclusionQuery.h @ 1812

/*
-----------------------------------------------------------------------------
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.
-----------------------------------------------------------------------------
*/
#ifndef _HardwareOcclusionQuery__
#define _HardwareOcclusionQuery__

// Precompiler options
#include "OgrePrerequisites.h"

namespace Ogre {



/**
  * This is a abstract class that that provides the interface for the query class for 
  * hardware occlusion.
  *
  * @author Lee Sandberg
  * Updated on 13/8/2005 by Tuan Kuranes email: tuan.kuranes@free.fr
  */
class _OgreExport HardwareOcclusionQuery
{
//----------------------------------------------------------------------
// Public methods
//--
public:
        /**
          * Object public member functions
          */

        /**
          * Default object constructor
          * 
          */
        HardwareOcclusionQuery();

        /**
          * Object destructor
          */
        virtual ~HardwareOcclusionQuery();

        /**
          * Starts the hardware occlusion query
          * @Remarks    Simple usage: Create one or more OcclusionQuery object one per outstanding query or one per tested object 
          *                             OcclusionQuery* m_pOcclusionQuery;
          *                             createOcclusionQuery( &m_pOcclusionQuery );
          *                             In the rendering loop:
          *                             Draw all occluders
          *                             m_pOcclusionQuery->startOcclusionQuery();
          *                             Draw the polygons to be tested
          *                             m_pOcclusionQuery->endOcclusionQuery();
          *
          *                             Results must be pulled using:
          *                             UINT    m_uintNumberOfPixelsVisable;
          *                             pullOcclusionQuery( &m_dwNumberOfPixelsVisable );
          *                     
          */
        virtual void beginOcclusionQuery() = 0;

        /**
          * Ends the hardware occlusion test
          */
        virtual void endOcclusionQuery() = 0;

        /**
      * Pulls the hardware occlusion query.
          * @note Waits until the query result is available; use isStillOutstanding
          *             if just want to test if the result is available.
      * @retval NumOfFragments will get the resulting number of fragments.
      * @return True if success or false if not.
      */
        virtual bool pullOcclusionQuery(unsigned int* NumOfFragments) = 0;

        /**
          * Let's you get the last pixel count with out doing the hardware occlusion test
          * @return The last fragment count from the last test.
          * Remarks This function won't give you new values, just the old value.
          */
        unsigned int getLastQuerysPixelcount() const { return mPixelCount; }

        /**
          * Lets you know when query is done, or still be processed by the Hardware
          * @return true if query isn't finished.
          */
         virtual bool isStillOutstanding(void) = 0; 


    //----------------------------------------------------------------------
    // protected members
    //--
    protected :
        // numbers of visible pixels determined by last query
        unsigned int mPixelCount;
        // is query hasn't yet returned a result.
                bool             mIsQueryResultStillOutstanding;
};

}
#endif