[simgear.git] / simgear / sky / sky.hxx

/**
 * \file sky.hxx
 * Provides a class to model a realistic (time/date/position) based sky.
 */

// Written by Curtis Olson, started December 1997.
// SSG-ified by Curtis Olson, February 2000.
//
// Copyright (C) 1997-2000  Curtis L. Olson  - curt@flightgear.org
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library 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
// Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public
// License along with this library; if not, write to the
// Free Software Foundation, Inc., 59 Temple Place - Suite 330,
// Boston, MA  02111-1307, USA.
//
// $Id$


#ifndef _SG_SKY_HXX
#define _SG_SKY_HXX


#ifndef __cplusplus                                                          
# error This library requires C++
#endif                                   


#include <plib/ssg.h>           // plib include

#include <simgear/compiler.h>
#include <simgear/misc/sg_path.hxx>

#include <vector>

#include <simgear/sky/cloud.hxx>
#include <simgear/sky/dome.hxx>
#include <simgear/sky/moon.hxx>
#include <simgear/sky/oursun.hxx>
#include <simgear/sky/stars.hxx>

SG_USING_STD(vector);


typedef vector < SGCloudLayer* > layer_list_type;
typedef layer_list_type::iterator layer_list_iterator;
typedef layer_list_type::const_iterator layer_list_const_iterator;

/**
 * A class to model a realistic (time/date/position) based sky.
 *
 * Introduction 
 *
 * The SGSky class models a blended sky dome, a haloed sun, a textured
 * moon with phase that properly matches the date, stars and planets,
 * and cloud layers. SGSky is designed to be dropped into existing
 * plib based applications and depends heavily on plib's scene graph
 * library, ssg. The sky implements various time of day lighting
 * effects, it plays well with fog and visibility effects, and
 * implements scudded cloud fly-through effects. Additionally, you can
 * wire in the output of the SGEphemeris class to accurately position
 * all the objects in the sky.
 *
 * Building the sky 
 *

 * Once you have created an instance of SGSky you must call the
 * build() method.  Building the sky requires several textures. So,
 * you must specify the path/directory where these textures reside
 * before building the sky.  You do this first by calling the
 * texture_path() method.

 * The arguments you pass to the build() method allow you to specify
 * the size of your sun sphere and moon sphere, a number of planets,
 * and a multitude of stars.  For the planets and stars you pass in an
 * array of right ascensions, declinations, magnitudes, and the
 * distance from the view point.

 * Cloud Layers 

 * Cloud layers can be added, changed, or removed individually. To add
 * a cloud layer use the add_cloud_layer() method.  The arguments
 * allow you to specify base height above sea level, layer thickness,
 * a transition zone for entering/leaving the cloud layer, the size of
 * the cloud object, and the type of cloud texture. All distances are
 * in meters. There are additional forms of this method that allow you
 * to specify your own ssgSimpleState or texture name for drawing the
 * cloud layer.

 * Repainting the Sky 

 * As the sun circles the globe, you can call the repaint() method to
 * recolor the sky objects to simulate sunrise and sunset effects,
 * visibility, and other lighting changes.  The arguments allow you to
 * specify a base sky color (for the top of the dome), a fog color
 * (for the horizon), the sun angle with the horizon (for
 * sunrise/sunset effects), the moon angle (so we can make it more
 * yellow at the horizon), and new star and planet data so that we can
 * optionally change the magnitude of these (for day / night
 * transitions.)

 * Positioning Sky Objects 

 * As time progresses and as you move across the surface of the earth,
 * the apparent position of the objects and the various lighting
 * effects can change. the reposition() method allows you to specify
 * the positions of all the sky objects as well as your view position.
 * The arguments allow you to specify your view position in world
 * Cartesian coordinates, the zero elevation position in world
 * Cartesian coordinates (your longitude, your latitude, sea level),
 * the ``up'' vector in world Cartesian coordinates, current
 * longitude, latitude, and altitude. A ``spin'' angle can be
 * specified for orienting the sky with the sun position so sunset and
 * sunrise effects look correct. You must specify GMT side real time,
 * the sun right ascension, sun declination, and sun distance from
 * view point (to keep it inside your view volume.) You also must
 * specify moon right ascension, moon declination, and moon distance
 * from view point.

 * Rendering the Sky 

 * The sky is designed to be rendered in two stages. The first stage
 * renders the parts that form your back drop - the sky dome, the
 * stars and planets, the sun, and the moon.  These should be rendered
 * before the rest of your scene by calling the preDraw() method. The
 * second stage renders the clouds which are likely to be translucent
 * (depending on type) and should be drawn after your scene has been
 * rendered.  Use the postDraw() method to draw the second stage of
 * the sky.

 * A typical application might do the following: 

 * <li> thesky->preDraw();
 * <li> ssgCullAndDraw ( myscene ) ;
 * <li> thesky->postDraw( my_altitude );

 * The current altitude in meters is passed to the postDraw() method
 * so the clouds layers can be rendered correction from most distant
 * to closest.

 * Visibility Effects 

 * Visibility and fog is important for correctly rendering the
 * sky. You can inform SGSky of the current visibility by calling the
 * set_visibility() method.

 * When transitioning through clouds, it is nice to pull in the fog as
 * you get close to the cloud layer to hide the fact that the clouds
 * are drawn as a flat polygon. As you get nearer to the cloud layer
 * it is also nice to temporarily pull in the visibility to simulate
 * the effects of flying in and out of the puffy edge of the
 * cloud. These effects can all be accomplished by calling the
 * modify_vis() method.  The arguments allow you to specify your
 * current altitude (which is then compared to the altitudes of the
 * various cloud layers.) You can also specify a time factor which
 * should be the length in seconds since the last time you called
 * modify_vis(). The time_factor value allows the puffy cloud effect
 * to be calculated correctly.

 * The modify_vis() method alters the SGSky's internal idea of
 * visibility, so you should subsequently call get_visibility() to get
 * the actual modified visibility. You should then make the
 * appropriate glFog() calls to setup fog properly for your scene.

 * Accessor Methods 

 * Once an instance of SGSky has been successfully initialized, there
 * are a couple accessor methods you can use such as get_num_layers()
 * to return the number of cloud layers, get_cloud_layer(i) to return
 * cloud layer number i, get_visibility() to return the actual
 * visibility as modified by the sky/cloud model.

 */

class SGSky {

private:

    // components of the sky
    SGSkyDome *dome;
    SGSun *oursun;
    SGMoon *moon;
    SGStars *planets;
    SGStars *stars;
    ssgSimpleState *cloud_mats[SG_MAX_CLOUD_TYPES];
    layer_list_type cloud_layers;

    ssgRoot *pre_root, *post_root;

    ssgSelector *pre_selector, *post_selector;
    ssgTransform *pre_transform, *post_transform;

    SGPath tex_path;

    // visibility
    float visibility;
    float effective_visibility;

    // near cloud visibility state variables
    bool in_puff;
    double puff_length;         // in seconds
    double puff_progression;    // in seconds
    double ramp_up;             // in seconds
    double ramp_down;           // in seconds

public:

    /** Constructor */
    SGSky( void );

    /** Destructor */
    ~SGSky( void );

    /**
     * Initialize the sky and connect the components to the scene
     * graph at the provided branch.  See discussion in detailed class
     * description.
     * @param sun_size size of sun
     * @param moon_size size of moon
     * @param nplanets number of planets
     * @param planet_data an array of planet right ascensions, declinations,
     *        and magnitudes
     * @param planet_dist distance from viewer to put the planets
     * @param nstars number of stars
     * @param star_data an array of star right ascensions, declinations,
     *        and magnitudes
     * @param star_dist distance from viewer to put the stars */
    void build( double sun_size, double moon_size,
                int nplanets, sgdVec3 *planet_data, double planet_dist,
                int nstars, sgdVec3 *star_data, double star_dist );

    /**
     * Repaint the sky components based on current value of sun_angle,
     * sky, and fog colors.  You can also specify new star and planet
     * data so that we can optionally change the magnitude of these
     * (for day/night transitions.)  See discussion in detailed
     * class description.
     *
     * Sun and moon angles are specified in degrees relative to local up
     * <li> 0 degrees = high noon
     * <li> 90 degrees = sun rise/set
     * <li> 180 degrees = darkest midnight
     * @param sky_color the base sky color (for the top of the dome)
     * @param fog_color the fog color (for the horizon)
     * @param sun_angle the sun angle with the horizon (for sunrise/sunset
     *        effects)
     * @param moon_angle the moon angle (so we can make it more yellow
     *        at the horizon)
     * @param nplanets number of planets
     * @param planet_data an array of planet right ascensions, declinations,
     *        and magnitudes
     * @param nstars number of stars
     * @param star_data an array of star right ascensions, declinations,
     *        and magnitudes
     */
    bool repaint( sgVec4 sky_color, sgVec4 fog_color,
                  double sun_angle, double moon_angle,
                  int nplanets, sgdVec3 *planet_data,
                  int nstars, sgdVec3 *star_data );

    /**
     * Reposition the sky at the specified origin and orientation
     *
     * lon specifies a rotation about the Z axis
     * lat specifies a rotation about the new Y axis
     * spin specifies a rotation about the new Z axis (this allows
     * additional orientation for the sunrise/set effects and is used
     * by the skydome and perhaps clouds.  See discussion in detailed
     * class description.
     * @param view_pos specify your view position in world Cartesian
     *        coordinates
     * @param zero_elev the zero elevation position in world Cartesian
     *        coordinates
     * @param view_up the up vector in world Cartesian coordinates
     * @param lon current longitude
     * @param lat current latitude
     * @param alt current altitude
     * @param spin an offset angle for orienting the sky effects with the
     *        sun position so sunset and sunrise effects look correct.
     * @param gst GMT side real time
     * @param sun_ra the sun's current right ascension
     * @param sun_dec the sun's current declination
     * @param sun_dist the sun's distance from the current view point
     *        (to keep it inside your view volume.)
     * @param moon_ra the moon's current right ascension
     * @param moon_dec the moon's current declination
     * @param moon_dist the moon's distance from the current view point. 
     */
    bool reposition( sgVec3 view_pos, sgVec3 zero_elev, sgVec3 view_up,
                     double lon, double lat, double alt, double spin,
                     double gst, 
                     double sun_ra, double sun_dec, double sun_dist,
                     double moon_ra, double moon_dec, double moon_dist );

    /**
     * Modify the given visibility based on cloud layers, thickness,
     * transition range, and simulated "puffs".  See discussion in detailed
     * class description.
     * @param alt current altitude
     * @param time_factor amount of time since modify_vis() last called so
     *        we can scale effect rates properly despite variable frame rates.
     */
    void modify_vis( float alt, float time_factor );

    /**
     * Draw background portions of the sky ... do this before you draw
     * the rest of your scene.  See discussion in detailed
     * class description.
     */
    void preDraw();

    /**
     * Draw translucent clouds ... do this after you've drawn all the
     * oapaque elements of your scene.  See discussion in detailed
     * class description.
     * @param alt current altitude
     */
    void postDraw( float alt );

    /** 
     * Specify the texture path (optional, defaults to current directory)
     * @param path base path to texture locations
     */
    inline void texture_path( const string& path ) {
        tex_path = SGPath( path );
    }

    /** Enable drawing of the sky. */
    inline void enable() {
        pre_selector->select( 1 );
        post_selector->select( 1 );
    }

    /**
     * Disable drawing of the sky in the scene graph.  The leaf node is still
     * there, how ever it won't be traversed on by ssgCullandRender()
     */
    inline void disable() {
        pre_selector->select( 0 );
        post_selector->select( 0 );
    }

    /**
     * Add a cloud layer (distances in meters).
     * @param asl cloud base height above sea level
     * @param thickness cloud layer thickness
     * @param transition thickness of transition layer from 100% out of 
     *        cloud to 100% in cloud.  Used for scudded clouds effect.
     * @param span horizontal size of cloud object
     * @param type type of cloud (chosen from available cloud types)
     */
    void add_cloud_layer( double asl, double thickness,
                          double transition, double span,
                          SGCloudType type );

    /**
     * Add a cloud layer (distances in meters).
     * @param asl cloud base height above sea level
     * @param thickness cloud layer thickness
     * @param transition thickness of transition layer from 100% out of 
     *        cloud to 100% in cloud.  Used for scudded clouds effect.
     * @param span horizontal size of cloud object
     * @param tex_path file name of a cloud texture
     */
    void add_cloud_layer( double asl, double thickness,
                          double transition, double span,
                          const string &tex_path );

    /**
     * Add a cloud layer (distances in meters).
     * @param asl cloud base height above sea level
     * @param thickness cloud layer thickness
     * @param transition thickness of transition layer from 100% out of 
     *        cloud to 100% in cloud.  Used for scudded clouds effect.
     * @param span horizontal size of cloud object
     * @param state pointer to an existing ssgSimpleState
     */
    void add_cloud_layer( double asl, double thickness,
                          double transition, double span,
                          ssgSimpleState *state );

    /** @return number of cloud layers */
    inline int get_num_layers() const { return cloud_layers.size(); }

    /**
     * Get a cloud layer
     * @param i which cloud layer
     * @return cloud layer number i */
    inline SGCloudLayer *get_cloud_layer( int i ) const {
        return cloud_layers[i];
    }

    /** @return current effective visibility */
    inline float get_visibility() const { return effective_visibility; }

    /** Set desired clear air visibility.
     * @param v visibility in meters
     */
    inline void set_visibility( float v ) {
        effective_visibility = visibility = v;
    }
};


#endif // _SG_SKY_HXX