// OpenCSG - library for image-based CSG rendering for OpenGL
// Copyright (C) 2002-2023, Florian Kirsch,
// Hasso-Plattner-Institute at the University of Potsdam, Germany
//
// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This library 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110 - 1301 USA.

//
// occlusionQuery.h
//
// wrappers parts of different occlusion-query extensions conveniently
//

#ifndef __OpenCSG__occlusion_query_h__
#define __OpenCSG__occlusion_query_h__

#include "opencsgConfig.h"

namespace OpenCSG {

    namespace OpenGL {

        class OcclusionQuery {
        public: // abstract base class
            virtual ~OcclusionQuery() {};

            /// begins an occlusion query
            virtual void beginQuery() = 0;
            /// stops an occlusion query
            virtual void endQuery() = 0;
            /// returns the number of fragments that have been put into
            /// the frame buffer between beginQuery() and endQuery().
            /// if the parameter exactNumberNeeded of getOcclusionQuery()
            /// is false, the return value is just 0 or 1, depending
            /// whether any fragment has been rendered or not.
            virtual unsigned int getQueryResult() = 0;

        protected:
            OcclusionQuery() {};
        };

        /// checks for OpenGL-extensions and returns a matching occlusion
        /// query object. may return 0 if occlusion queries are not
        /// supported by graphics hardware.
        ///
        /// when the occlusion query object is not needed anymore,
        /// it must be deleted!
        OcclusionQuery* getOcclusionQuery(bool exactNumberNeeded);

    } // namespace OpenGL

} // namespace OpenCSG

#endif // __OpenCSG__occlusion_query_h__


