/* -*-c++-*- */
/* osgEarth - Dynamic map generation toolkit for OpenSceneGraph
 * Copyright 2016 Pelican Mapping
 * http://osgearth.org
 *
 * osgEarth 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, see <http://www.gnu.org/licenses/>
 */

#ifndef OSGEARTH_DRAW_INSTANCED_H
#define OSGEARTH_DRAW_INSTANCED_H 1

#include <osgEarth/Common>
#include <osgEarth/Containers>
#include <osgEarth/VirtualProgram>
#include <osg/NodeVisitor>
#include <osg/Geode>

/**
 * Some utilities to support *DrawInstanced rendering.
 */
namespace osgEarth
{
    namespace DrawInstanced
    {
        /**
         * Referenced-counted vector of instance matrices. These are stored
         * in the node that's been instanced so the app can recover the 
         * original positioning data.
         */
        class MatrixRefVector : public osgEarth::MixinVector<osg::Matrixf,osg::Object>
        {
        public:
            META_Object(osgEarth,MatrixRefVector);
            MatrixRefVector() : osgEarth::MixinVector<osg::Matrixf,osg::Object>() { }
        protected:
            MatrixRefVector(const MatrixRefVector& rhs, const osg::CopyOp& op) { }
        };

        /**
         * Visitor that converts all the primitive sets in a graph to use
         * instanced draw calls.
         * Called by convertGraphToUseDrawInstanced().
         */
        class OSGEARTH_EXPORT ConvertToDrawInstanced : public osg::NodeVisitor
        {
        public:
            /**
             * Create the visitor that will convert primitive sets to draw
             * <num> instances.
             */
            ConvertToDrawInstanced(
                unsigned                numInstances,
                const osg::BoundingBox& bbox,
                bool                    optimize );

            void apply(osg::Geode&);
            void apply(osg::LOD&);

        protected:
            unsigned _numInstances;
            osg::BoundingBox _bbox;
            bool _optimize;
            std::list<osg::PrimitiveSet*> _primitiveSets;
        };


        /**
         * Creates a virtual shader program that implements DrawInstanced rendering.
         * You should prepare the scene graph first by calling
         * convertGraphToUseDrawInstanced().
         * @return false If instancing is not available
         */
        extern OSGEARTH_EXPORT bool install(osg::StateSet* stateset);
        extern OSGEARTH_EXPORT void remove (osg::StateSet* stateset);


        /**
         * Processes a scene graph and converts all the top-level MatrixTransform
         * nodes into shader uniforms that can be used with the VirtualProgram
         * created by createDrawInstacedShaders.
         * NOTE: You must also call install(StateSet) to activate instancing.
         * @return false If instancing is not available
         */
        extern OSGEARTH_EXPORT bool convertGraphToUseDrawInstanced( 
            osg::Group* graph );

        /**
         * Gets the vector of instance matrices attached to a node,
         * or NULL if not found.
         */
        extern OSGEARTH_EXPORT const MatrixRefVector* getMatrixVector(
            osg::Node* node );
    }
}

#endif // OSGEARTH_DRAW_INSTANCED_H
