SphereSegment

/* -*-c++-*- OpenSceneGraph - Copyright (C) 1998-2006 Robert Osfield
 *
 * This library is open source and may be redistributed and/or modified under
 * the terms of the OpenSceneGraph Public License (OSGPL) version 0.0 or
 * (at your option) any later version.  The full license is in LICENSE file
 * included with this distribution, and on the openscenegraph.org website.
 *
 * 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
 * OpenSceneGraph Public License for more details.
*/

#ifndef OSGSIM_SPHERESEGMENT
#define OSGSIM_SPHERESEGMENT 1

#include <osgSim/Export>

#include <osg/Vec3>
#include <osg/Vec4>
#include <osg/Geode>
#include <osg/Matrixd>
#include <osg/BlendFunc>

namespace osgSim{

/**
A SphereSegment is a Geode to represent an portion of a sphere (potentially
the whole sphere). The sphere is aligned such that the line through the
sphere's poles is parallel to the z axis. The sphere segment
may be rendered various components switched on or off:

    - The specified area of the sphere surface.

    - An edge line around the boundary of the specified area
      of the sphere surface.

    - Four <i>spokes</i>, where a spoke is the line from
      the sphere's centre to a corner of the rendered area.

    - Four planar areas, where the planar areas are formed
      between the spokes.

Caveats:

    - It's worth noting that the line through the sphere's poles is
      parallel to the z axis. This has implications when specifying the
      area to be rendered, and specifying areas where the centre of
      the rendered area <i>is</i> the Z axis may lead to unexpected
      geometry.

    - It's possible to render the whole sphere by specifying elevation
      and azimuth ranges round the full 360 degrees. When doing
      so you may consider switching the planes, spokes, and edge lines
      off, to avoid rendering artefacts, e.g. the upper and lower
      planes will be coincident.

*/
class OSGSIM_EXPORT SphereSegment: public osg::Geode
{
public:

    /**
    DrawMask represents a bit field, the values of which may be OR'ed together
    to specify which parts of the sphere segment should be drawn. E.g.
    \code
    sphereSegment->setDrawMask(SphereSegment::DrawMask(SphereSegment::SURFACE|SphereSegment::SPOKES));
    \endcode
    */
    enum DrawMask{
        SURFACE =   0x00000001, ///< Draw the specified area on the sphere's surface
        SPOKES =    0x00000002, ///< Draw the spokes from the sphere's centre to the surface's corners
        EDGELINE =  0x00000008, ///< Draw the line round the edge of the area on the sphere's surface
        SIDES =     0x00000010, ///< Draw the planes from the sphere's centre to the edge of the sphere's surface
        ALL =       0x7fffffff  ///< Draw every part of the sphere segment
    };


    /** Default constructor. */
    SphereSegment():osg::Geode(),
                    _centre(0.0f,0.0f,0.0f), _radius(1.0f),
                    _azMin(0.0f), _azMax(osg::PI/2.0f),
                    _elevMin(0.0f), _elevMax(osg::PI/2.0f),
                    _density(10),
                    _drawMask(DrawMask(ALL))
    {
        init();
    }

    /**
    Construct by angle ranges. Note that the azimuth 'zero' is the Y axis; specifying
    an azimuth range from azMin -osg::PI/2.0f to azMax osg::PI/2.0f will cover the
    'top half' of the circle in the XY plane. The elev angles are 'out' of the 'zero'
    XY plane with +ve angles above the plane, and -ve angles below.
    @param centre       sphere centre
    @param radius       radius of sphere
    @param azMin        azimuth minimum
    @param azMax        azimuth maximum
    @param elevMin      elevation minimum
    @param elevMax      elevation maximum
    @param density      number of units to divide the azimuth and elevation ranges into
    */
    SphereSegment(const osg::Vec3& centre, float radius, float azMin, float azMax,
                    float elevMin, float elevMax, int density):
        osg::Geode(),
        _centre(centre), _radius(radius),
        _azMin(azMin), _azMax(azMax),
        _elevMin(elevMin), _elevMax(elevMax),
        _density(density),
        _drawMask(DrawMask(ALL))
    {
        init();
    }

    /**
    Construct by vector.
    @param centre       sphere centre
    @param radius       radius of sphere
    @param vec          vector pointing from sphere centre to centre point
                        of rendered area on sphere surface
    @param azRange      azimuth range in radians (with centre along vec)
    @param elevRange    elevation range in radians (with centre along vec)
    @param density      number of units to divide the azimuth and elevation ranges into
    */
    SphereSegment(const osg::Vec3& centre, float radius, const osg::Vec3& vec, float azRange,
                    float elevRange, int density);

    /** Copy constructor */
    SphereSegment(const SphereSegment& rhs, const osg::CopyOp& co):
        osg::Geode(rhs,co),
        _centre(rhs._centre), _radius(rhs._radius),
        _azMin(rhs._azMin), _azMax(rhs._azMax),
        _elevMin(rhs._elevMin), _elevMax(rhs._elevMax),
        _density(rhs._density),
        _drawMask(rhs._drawMask)
    {
        init();
    }

    /** Set the centre point of the SphereSegment */
    void setCentre(const osg::Vec3& c);

    /** Get the centre point of the SphereSegment */
    const osg::Vec3& getCentre() const;

    /** Set the radius of the SphereSegment */
    void setRadius(float r);

    /** Get the radius of the SphereSegment */
    float getRadius() const;

    /** Set the area of the sphere segment

    @param vec          vector pointing from sphere centre to centre point
                        of rendered area on sphere surface
    @param azRange      azimuth range in radians (with centre along vec)
    @param elevRange    elevation range in radians (with centre along vec)
    */
    void setArea(const osg::Vec3& vec, float azRange, float elevRange);

    /** Get the area of the sphere segment

    @param vec          vector pointing from sphere centre to centre point
                        of rendered area on sphere surface (normalized)
    @param azRange      azimuth range in radians (with centre along vec)
    @param elevRange    elevation range in radians (with centre along vec)
    */
    void getArea(osg::Vec3& vec, float& azRange, float& elevRange) const;

    /** Set the area of the sphere segment
    @param azMin        azimuth minimum
    @param azMax        azimuth maximum
    @param elevMin      elevation minimum
    @param elevMax      elevation maximum
    */
    void setArea(float azMin, float azMax, float elevMin, float elevMax);

    /** Get the area of the sphere segment
    @param azMin        azimuth minimum
    @param azMax        azimuth maximum
    @param elevMin      elevation minimum
    @param elevMax      elevation maximum
    */
    void getArea(float &azMin, float &azMax, float &elevMin, float &elevMax) const;

    /** Set the density of the sphere segment */
    void setDensity(int d);

    /** Get the density of the sphere segment */
    int getDensity() const;

    /**
    Specify the DrawMask.
    @param dm   Bitmask specifying which parts of the sphere segment should be drawn.
    @see DrawMask
    */
    void setDrawMask(int dm);

    /** Get the DrawMask */
    int getDrawMask() const { return _drawMask; }

    /** Set the color of the surface. */
    void setSurfaceColor(const osg::Vec4& c);

    /** Get the color of the surface. */
    const osg::Vec4& getSurfaceColor() const { return _surfaceColor; }

    /** Set the color of the spokes. */
    void setSpokeColor(const osg::Vec4& c);

    /** Get the color of the spokes. */
    const osg::Vec4& getSpokeColor() const { return _spokeColor; }

    /** Set the color of the edge line. */
    void setEdgeLineColor(const osg::Vec4& c);

    /** Get the color of the edge line. */
    const osg::Vec4& getEdgeLineColor() const { return _edgeLineColor; }

    /** Set the color of the planes. */
    void setSideColor(const osg::Vec4& c);

    /** Get the color of the planes. */
    const osg::Vec4& getSideColor() const { return _planeColor; }

    /** Set color of all components. */
    void setAllColors(const osg::Vec4& c);

    META_Node(osgSim, SphereSegment);
    
    /** A list of vertex arrays representing a list of lines.*/
    typedef std::vector< osg::ref_ptr<osg::Vec3Array> > LineList;
    
    /** Compute the interesection lines between subgraph and this sphere segment.
      * The matrix is the transform that takes the subgraph into the same coordiante frame as the sphere segment.
      * The resulting intersections are in the coordinate frame of the sphere segment. */
    LineList computeIntersection(const osg::Matrixd& matrix, osg::Node* subgraph);

    /** Compute the interesection lines between specified drawable and this sphere segment.
      * The matrix is the transform that takes the subgraph into the same coordiante frame as the sphere segment.
      * The resulting intersections are in the coordinate frame of the sphere segment. */
    LineList computeIntersection(const osg::Matrixd& matrix, osg::Drawable* drawable);

    /** Compute the interesection lines between subgraph and this sphere segment.
      * The matrix is the transform that takes the subgraph into the same coordiante frame as the sphere segment.
      * The resulting intersections are in the coordinate frame of the sphere segment. */
    osg::Node* computeIntersectionSubgraph(const osg::Matrixd& matrix, osg::Node* subgraph);

    /** Compute the interesection lines between specified drawable and this sphere segment.
      * The matrix is the transform that takes the subgraph into the same coordiante frame as the sphere segment.
      * The resulting intersections are in the coordinate frame of the sphere segment. */
    osg::Node* computeIntersectionSubgraph(const osg::Matrixd& matrix, osg::Drawable* drawable);


private:

    void init();    // Shared constructor code, generates the drawables

    void dirtyAllDrawableDisplayLists();    // Force re-calling of gl functions
    void dirtyAllDrawableBounds();          // Force recalculation of bound geometry

    // SphereSegment is actually made up of a number of Drawable classes,
    // all of which are nested private classes, as declared below. These
    // classes are defined in the .cpp for minimum visibility and physical
    // coupling. (Reduces time spent compiling! :-)
    //
    // Each of the nested classes holds a pointer to the SphereSegment
    // 'parent', which stores the geometry details, and performs any
    // work required. The nested classes are lightweight objects which
    // just pass the work on.
    //
    // Why are things done with these sub-Drawables? Alpha-blended
    // Drawables need to be drawn last, depth sorted, and the various
    // components of a SphereSegment also need to be depth sorted
    // against one another (they may all be drawn with alpha blending).
    // Making these Drawables allows us to get the OSG to depth sort
    // for us.

    class Surface;
    friend class Surface;
    bool Surface_computeBound(osg::BoundingBox&) const;
    void Surface_drawImplementation(osg::State&) const;

    class EdgeLine;
    friend class EdgeLine;
    bool EdgeLine_computeBound(osg::BoundingBox&) const;
    void EdgeLine_drawImplementation(osg::State&) const;

    enum BoundaryAngle{MIN,MAX};        // Why here and not in Side class? Because we can't forward
    enum SideOrientation{AZIM,ELEV};   // declare enums, Side is in the .cpp, and this is tidier...
    class Side;
    friend class Side;
    bool Side_computeBound(osg::BoundingBox&, SideOrientation, BoundaryAngle) const;
    void Side_drawImplementation(osg::State&, SideOrientation, BoundaryAngle) const;

    class Spoke;
    friend class Spoke;
    bool Spoke_computeBound(osg::BoundingBox&, BoundaryAngle, BoundaryAngle) const;
    void Spoke_drawImplementation(osg::State&, BoundaryAngle, BoundaryAngle) const;

    // Sphere segment geometry details
    osg::Vec3 _centre;
    float _radius;
    float _azMin, _azMax, _elevMin, _elevMax;
    int _density;

    // Draw details
    int         _drawMask;
    osg::Vec4   _surfaceColor;
    osg::Vec4   _spokeColor;
    osg::Vec4   _edgeLineColor;
    osg::Vec4   _planeColor;
};

}

#endif