Collaboration diagram for osgEarth::ElevationQuery:

Public Types
enum	Technique { TECHNIQUE_GEOMETRIC, TECHNIQUE_PARAMETRIC }
Public Member Functions
	ElevationQuery (const Map *map)
	ElevationQuery (const MapFrame &mapFrame)
bool	getElevation (const osg::Vec3d &point, const SpatialReference pointSRS, double &out_elevation, double desiredResolution=0.0, double out_actualResolution=0L)
bool	getElevations (std::vector< osg::Vec3d > &points, const SpatialReference *pointsSRS, bool ignoreZ=true, double desiredResolution=0.0)
bool	getElevations (const std::vector< osg::Vec3d > &points, const SpatialReference *pointsSRS, std::vector< double > &out_elevations, double desiredResolution=0.0)
void	setTechnique (Technique technique)
Technique	getTechnique () const
void	setMaxTilesToCache (int value)
int	getMaxTilesToCache () const
void	setInterpolation (ElevationInterpolation interp)
ElevationInterpolation	getElevationInterpolation () const
void	setMaxLevelOverride (int maxLevelOverride)
int	getMaxLevelOverride () const
Private Types
typedef LRUCache< TileKey, osg::ref_ptr < osgTerrain::TerrainTile > >	TileCache
Private Member Functions
void	postCTOR ()
void	sync ()
bool	getElevationImpl (const osg::Vec3d &point, const SpatialReference pointSRS, double &out_elevation, double desiredResolution, double out_actualResolution=0L)
Private Attributes
MapFrame	_mapf
unsigned	_maxCacheSize
int	_tileSize
unsigned int	_maxDataLevel
int	_maxLevelOverride
Technique	_technique
ElevationInterpolation	_interpolation
TileCache	_tileCache

Detailed Description

ElevationQuery (EQ) lets you query the elevation at any point on a map.

Rather than intersecting with a loaded scene graph, EQ uses the osgEarth engine to directly access the best terrain tile for elevation query. You give it the DEM resolution at which you want an elevation point, and it will access the necessary tile and sample it.

EQ supports two types of sampling:

PARAMTERIC - EQ will sample the actual heightfield directly. This method is the fastest since it does not require geometry intersection testing.

GEOMETRIC - EQ will create a temporary tesselated terrain tile and do an intersection test (using osgUtil::IntersectionVisitor). This method is slower but more visually correlated. (TODO: not really true anymore. This method will require a re-do in osgEarth 2.2 or 3.0)

NOTE: EQ does NOT take into account rendering properties like vertical scale or skirts. If you need a vertical scale, for example, simply scale the resulting elevation value.

Definition at line 50 of file ElevationQuery.

Member Typedef Documentation

typedef LRUCache< TileKey, osg::ref_ptr<osgTerrain::TerrainTile> > osgEarth::ElevationQuery::TileCache [private]

Definition at line 176 of file ElevationQuery.

Member Enumeration Documentation

enum osgEarth::ElevationQuery::Technique

Technique for elevation data sampling - see setTechnique

Enumerator:

TECHNIQUE_GEOMETRIC	Intersect with triangulated geometry - using the highest resolution data available from the Map source layers
TECHNIQUE_PARAMETRIC	Sample height from the parametric heightfield directly (bilinear)

Definition at line 54 of file ElevationQuery.

        {
            TECHNIQUE_GEOMETRIC,

            TECHNIQUE_PARAMETRIC
        };

Constructor & Destructor Documentation

ElevationQuery::ElevationQuery ( const Map * map )

Constructs a new elevation manager. If you are not using a MapNode, use this constructor to perform elevation queries against a Map. If you *do* have a MapNode, use the other CTOR that takes a MapNode.

Parameters:

map	Map against which to perform elevation queries.
technique	Technique to use for elevation data sampling.

Definition at line 13 of file ElevationQuery.cpp.

                                               :
_mapf( map, Map::ELEVATION_LAYERS )
{
    postCTOR();
}

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ElevationQuery::ElevationQuery ( const MapFrame & mapFrame )

Definition at line 19 of file ElevationQuery.cpp.

                                                         :
_mapf( mapFrame )
{
    postCTOR();
}

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Member Function Documentation

bool ElevationQuery::getElevation	(	const osg::Vec3d &	point,
		const SpatialReference *	pointSRS,
		double &	out_elevation,
		double	desiredResolution = `0.0`,
		double *	out_actualResolution = `0L`
	)

Gets the terrain elevation at a point, given a terrain resolution.

Parameters:

point	Map coordinates for which to query elevation.
pointSRS	Spatial reference of "point" and "desiredResolution" If this is NULL, assume that the input values are expressed in terms of the Map's SRS.
out_elevation	Stores the elevation result in this variable upon success.
desiredResolution	Optimal resolution of elevation data to use for the query (if available). Pass in 0 (zero) to use the best available resolution.
out_resolution	Resolution of the resulting elevation value (if the method returns true).

Returns:: True if the query succeeded, false upon failure.

Definition at line 99 of file ElevationQuery.cpp.

{
    sync();
    return getElevationImpl( point, pointSRS, out_elevation, desiredResolution, out_actualResolution );
}

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bool ElevationQuery::getElevationImpl	(	const osg::Vec3d &	point,
		const SpatialReference *	pointSRS,
		double &	out_elevation,
		double	desiredResolution,
		double *	out_actualResolution = `0L`
	)		`[private]`

Definition at line 147 of file ElevationQuery.cpp.

{
    if ( _maxDataLevel == 0 || _tileSize == 0 )
    {
        // this means there are no heightfields.
        out_elevation = 0.0;
        return true;
    }
   
    // this is the ideal LOD for the requested resolution:
    unsigned int idealLevel = desiredResolution > 0.0
        ? _mapf.getProfile()->getLevelOfDetailForHorizResolution( desiredResolution, _tileSize )
        : _maxDataLevel;        

    // based on the heightfields available, this is the best we can theorically do:
    unsigned int bestAvailLevel = osg::minimum( idealLevel, _maxDataLevel );
    if (_maxLevelOverride >= 0)
    {
        bestAvailLevel = osg::minimum(bestAvailLevel, (unsigned int)_maxLevelOverride);
    }
    
    // transform the input coords to map coords:
    osg::Vec3d mapPoint = point;
    if ( pointSRS && !pointSRS->isEquivalentTo( _mapf.getProfile()->getSRS() ) )
    {
        if ( !pointSRS->transform2D( point.x(), point.y(), _mapf.getProfile()->getSRS(), mapPoint.x(), mapPoint.y() ) )
        {
            OE_WARN << LC << "Fail: coord transform failed" << std::endl;
            return false;
        }
    }

    osg::ref_ptr<osg::HeightField> hf;
    osg::ref_ptr<osgTerrain::TerrainTile> tile;

    // get the tilekey corresponding to the tile we need:
    TileKey key = _mapf.getProfile()->createTileKey( mapPoint.x(), mapPoint.y(), bestAvailLevel );
    if ( !key.valid() )
    {
        OE_WARN << LC << "Fail: coords fall outside map" << std::endl;
        return false;
    }

    // Check the tile cache. Note that the TileSource already likely has a MemCache
    // attached to it. We employ a secondary cache here for a couple reasons. One, this
    // cache will store not only the heightfield, but also the tesselated tile in the event
    // that we're using GEOMETRIC mode. Second, since the call the getHeightField can 
    // fallback on a lower resolution, this cache will hold the final resolution heightfield
    // instead of trying to fetch the higher resolution one each tiem.

    TileCache::Record record = _tileCache.get( key );
    if ( record.valid() )
        tile = record.value().get();
         
    // if we found it, make sure it has a heightfield in it:
    if ( tile.valid() )
    {
        osgTerrain::HeightFieldLayer* layer = dynamic_cast<osgTerrain::HeightFieldLayer*>(tile->getElevationLayer());
        if ( layer )
            hf = layer->getHeightField();

        if ( !hf.valid() )
            tile = 0L;
    }

    // if we didn't find it (or it didn't have heightfield data), build it.
    if ( !tile.valid() )
    {
        // generate the heightfield corresponding to the tile key, automatically falling back
        // on lower resolution if necessary:
        _mapf.getHeightField( key, true, hf, 0L, _interpolation );

        // bail out if we could not make a heightfield a all.
        if ( !hf.valid() )
        {
            OE_WARN << LC << "Unable to create heightfield for key " << key.str() << std::endl;
            return false;
        }

        // All this stuff is requires for GEOMETRIC mode. An optimization would be to
        // defer this so that PARAMETRIC mode doesn't waste time
        GeoLocator* locator = GeoLocator::createForKey( key, _mapf.getMapInfo() );

        tile = new osgTerrain::TerrainTile();

        osgTerrain::HeightFieldLayer* layer = new osgTerrain::HeightFieldLayer( hf.get() );
        layer->setLocator( locator );

        tile->setElevationLayer( layer );
        tile->setRequiresNormals( false );
        tile->setTerrainTechnique( new osgTerrain::GeometryTechnique );

        // store it in the local tile cache.
        _tileCache.insert( key, tile.get() );
    }

    OE_DEBUG << LC << "LRU Cache, hit ratio = " << _tileCache.getStats()._hitRatio << std::endl;

    // see what the actual resolution of the heightfield is.
    if ( out_actualResolution )
        *out_actualResolution = (double)hf->getXInterval();

    // finally it's time to get a height value:
    if ( _technique == TECHNIQUE_PARAMETRIC )
    {
        const GeoExtent& extent = key.getExtent();
        double xInterval = extent.width()  / (double)(hf->getNumColumns()-1);
        double yInterval = extent.height() / (double)(hf->getNumRows()-1);
        out_elevation = (double) HeightFieldUtils::getHeightAtLocation( 
            hf.get(), mapPoint.x(), mapPoint.y(), extent.xMin(), extent.yMin(), xInterval, yInterval );
        return true;
    }
    else // ( _technique == TECHNIQUE_GEOMETRIC )
    {
        osg::Vec3d start, end, zero;

        if ( _mapf.getMapInfo().isGeocentric() )
        {
            const SpatialReference* mapSRS = _mapf.getProfile()->getSRS();

            mapSRS->transformToECEF( osg::Vec3d(mapPoint.y(), mapPoint.x(),  50000.0), start );
            mapSRS->transformToECEF( osg::Vec3d(mapPoint.y(), mapPoint.x(), -50000.0), end );
            mapSRS->transformToECEF( osg::Vec3d(mapPoint.y(), mapPoint.x(),      0.0), zero );
        }
        else // PROJECTED
        {
            start.set( mapPoint.x(), mapPoint.y(),  50000.0 );
            end.set  ( mapPoint.x(), mapPoint.y(), -50000.0 );
            zero.set ( mapPoint.x(), mapPoint.y(),      0.0 );
        }

        osgUtil::LineSegmentIntersector* i = new osgUtil::LineSegmentIntersector( start, end );
        osgUtil::IntersectionVisitor iv;
        iv.setIntersector( i );

        tile->accept( iv );

        osgUtil::LineSegmentIntersector::Intersections& results = i->getIntersections();
        if ( !results.empty() )
        {
            const osgUtil::LineSegmentIntersector::Intersection& result = *results.begin();
            osg::Vec3d isectPoint = result.getWorldIntersectPoint();
            out_elevation = (isectPoint-end).length2() > (zero-end).length2()
                ? (isectPoint-zero).length()
                : -(isectPoint-zero).length();
            return true;            
        }

        OE_DEBUG << LC << "No intersection" << std::endl;
        return false;
    }
}

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ElevationInterpolation ElevationQuery::getElevationInterpolation ( ) const

Gets the elevation interpolation to use when sampling data

Definition at line 93 of file ElevationQuery.cpp.

{
    return _interpolation;
}

bool ElevationQuery::getElevations	(	std::vector< osg::Vec3d > &	points,
		const SpatialReference *	pointsSRS,
		bool	ignoreZ = `true`,
		double	desiredResolution = `0.0`
	)

Gets elevations for a whole array of points, storing the result in the "z" element. If "ignoreZ" is false, the new Z value will be offset by the original Z value.

Definition at line 110 of file ElevationQuery.cpp.

{
    sync();
    for( osg::Vec3dArray::iterator i = points.begin(); i != points.end(); ++i )
    {
        double elevation;
        double z = (*i).z();
        if ( getElevationImpl( *i, pointsSRS, elevation, desiredResolution ) )
        {
            (*i).z() = ignoreZ ? elevation : elevation + z;
        }
    }
    return true;
}

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bool ElevationQuery::getElevations	(	const std::vector< osg::Vec3d > &	points,
		const SpatialReference *	pointsSRS,
		std::vector< double > &	out_elevations,
		double	desiredResolution = `0.0`
	)

Gets elevations for a whole array of points, storing the results in the "out_elevations" vector.

Definition at line 129 of file ElevationQuery.cpp.

{
    sync();
    for( osg::Vec3dArray::const_iterator i = points.begin(); i != points.end(); ++i )
    {
        double elevation;
        if ( getElevationImpl( *i, pointsSRS, elevation, desiredResolution ) )
        {
            out_elevations.push_back( elevation );
        }
    }
    return true;
}

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int osgEarth::ElevationQuery::getMaxLevelOverride ( ) const

Gets the maximum level override for elevation queries.

int ElevationQuery::getMaxTilesToCache ( ) const

Gets the maximum cache size for elevation tiles.

Definition at line 81 of file ElevationQuery.cpp.

{
    return _tileCache.getMaxSize();
}

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ElevationQuery::Technique ElevationQuery::getTechnique ( ) const

Gets the technique to use for height determination. See the Technique enum in this class.

Definition at line 63 of file ElevationQuery.cpp.

{
    return _technique;
}

void ElevationQuery::postCTOR ( ) [private]

Definition at line 26 of file ElevationQuery.cpp.

{
    _tileSize         = 0;
    _maxDataLevel     = 0;
    _technique        = TECHNIQUE_PARAMETRIC;
    _interpolation    = INTERP_BILINEAR;
    _maxLevelOverride = -1;

    // Limit the size of the cache we'll use to cache heightfields. This is an
    // LRU cache.
    _tileCache.setMaxSize( 50 );
}

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void ElevationQuery::setInterpolation ( ElevationInterpolation interp )

Sets the elevation interpolation to use when sampling data

Definition at line 87 of file ElevationQuery.cpp.

{
    _interpolation = interp;
}

void osgEarth::ElevationQuery::setMaxLevelOverride ( int maxLevelOverride )

Sets the maximum level override for elevation queries. A value of -1 turns off the override.

void ElevationQuery::setMaxTilesToCache ( int value )

Sets the maximum cache size for elevation tiles.

Definition at line 75 of file ElevationQuery.cpp.

{
    _tileCache.setMaxSize( value );
}

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void ElevationQuery::setTechnique ( ElevationQuery::Technique technique )

Sets the technique to use for height determination. See the Technique enum in this class. The default is TECHNIQUE_PARAMETRIC.

Definition at line 69 of file ElevationQuery.cpp.

{
    _technique = technique;
}

void ElevationQuery::sync ( ) [private]

Definition at line 40 of file ElevationQuery.cpp.

{
    if ( _mapf.sync() || _tileSize == 0 || _maxDataLevel == 0 )
    {
        _tileSize = 0;
        _maxDataLevel = 0;

        for( ElevationLayerVector::const_iterator i = _mapf.elevationLayers().begin(); i != _mapf.elevationLayers().end(); ++i )
        {
            // we need the maximum tile size
            int layerTileSize = i->get()->getTileSize();
            if ( layerTileSize > _tileSize )
                _tileSize = layerTileSize;

            // we also need the maximum available data level.
            unsigned int layerMaxDataLevel = i->get()->getMaxDataLevel();
            if ( layerMaxDataLevel > _maxDataLevel )
                _maxDataLevel = layerMaxDataLevel;
        }
    }
}