source: downloads/ogre_src_v1-9-0/OgreMain/include/OgreLodStrategy.h

/*
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This source file is part of OGRE
    (Object-oriented Graphics Rendering Engine)
For the latest info, see http://www.ogre3d.org/

Copyright (c) 2000-2013 Torus Knot Software Ltd

Permission is hereby granted, free of charge, to any person obtaining a copy
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The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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THE SOFTWARE.
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*/
#ifndef __Lod_Strategy_H__
#define __Lod_Strategy_H__

#include "OgrePrerequisites.h"

#include "OgreMesh.h"

#include "OgreMovableObject.h"
#include "OgreCamera.h"
#include "OgreHeaderPrefix.h"

namespace Ogre {

        /** \addtogroup Core
        *  @{
        */
        /** \addtogroup LOD
        *  @{
        */
        /** Strategy for determining level of detail.
    @remarks
        Generally, to create a new LOD strategy, all of the following will
        need to be implemented: getValueImpl, getBaseValue, transformBias,
        getIndex, sort, and isSorted.
        In addition, transformUserValue may be overridden.
    */
        class _OgreExport LodStrategy : public LodAlloc
    {
    protected:
        /** Name of this strategy. */
        String mName;

        /** Compute the LOD value for a given movable object relative to a given camera. */
        virtual Real getValueImpl(const MovableObject *movableObject, const Camera *camera) const = 0;

    public:
        /** Constructor accepting name. */
        LodStrategy(const String& name);

        /** Virtual destructor. */
        virtual ~LodStrategy();

        /** Get the value of the first (highest) level of detail. */
        virtual Real getBaseValue() const = 0;

        /** Transform LOD bias so it only needs to be multiplied by the LOD value. */
        virtual Real transformBias(Real factor) const = 0;

        /** Transform user supplied value to internal value.
        @remarks
            By default, performs no transformation.
        @remarks
            Do not throw exceptions for invalid values here, as the LOD strategy
            may be changed such that the values become valid.
        */
        virtual Real transformUserValue(Real userValue) const;

        /** Compute the LOD value for a given movable object relative to a given camera. */
        Real getValue(const MovableObject *movableObject, const Camera *camera) const;

        /** Get the index of the LOD usage which applies to a given value. */
        virtual ushort getIndex(Real value, const Mesh::MeshLodUsageList& meshLodUsageList) const = 0;

        /** Get the index of the LOD usage which applies to a given value. */
        virtual ushort getIndex(Real value, const Material::LodValueList& materialLodValueList) const = 0;

        /** Sort mesh LOD usage list from greatest to least detail */
        virtual void sort(Mesh::MeshLodUsageList& meshLodUsageList) const = 0;

        /** Determine if the LOD values are sorted from greatest detail to least detail. */
        virtual bool isSorted(const Mesh::LodValueList& values) const = 0;

        /** Assert that the LOD values are sorted from greatest detail to least detail. */
        void assertSorted(const Mesh::LodValueList& values) const;

        /** Get the name of this strategy. */
        const String& getName() const { return mName; }

    protected:
        /** Implementation of isSorted suitable for ascending values. */
        static bool isSortedAscending(const Mesh::LodValueList& values);
        /** Implementation of isSorted suitable for descending values. */
        static bool isSortedDescending(const Mesh::LodValueList& values);

        /** Implementation of sort suitable for ascending values. */
        static void sortAscending(Mesh::MeshLodUsageList& meshLodUsageList);
        /** Implementation of sort suitable for descending values. */
        static void sortDescending(Mesh::MeshLodUsageList& meshLodUsageList);

        /** Implementation of getIndex suitable for ascending values. */
        static ushort getIndexAscending(Real value, const Mesh::MeshLodUsageList& meshLodUsageList);
        /** Implementation of getIndex suitable for descending values. */
        static ushort getIndexDescending(Real value, const Mesh::MeshLodUsageList& meshLodUsageList);

        /** Implementation of getIndex suitable for ascending values. */
        static ushort getIndexAscending(Real value, const Material::LodValueList& materialLodValueList);
        /** Implementation of getIndex suitable for descending values. */
        static ushort getIndexDescending(Real value, const Material::LodValueList& materialLodValueList);

    };
        /** @} */
        /** @} */

} // namespace

#include "OgreHeaderSuffix.h"

#endif