3 * Provides a class to model a realistic (time/date/position) based sky.
6 // Written by Curtis Olson, started December 1997.
7 // SSG-ified by Curtis Olson, February 2000.
9 // Copyright (C) 1997-2000 Curtis L. Olson - http://www.flightgear.org/~curt
11 // This library is free software; you can redistribute it and/or
12 // modify it under the terms of the GNU Library General Public
13 // License as published by the Free Software Foundation; either
14 // version 2 of the License, or (at your option) any later version.
16 // This library is distributed in the hope that it will be useful,
17 // but WITHOUT ANY WARRANTY; without even the implied warranty of
18 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
19 // Library General Public License for more details.
21 // You should have received a copy of the GNU General Public License
22 // along with this program; if not, write to the Free Software
23 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
33 # error This library requires C++
37 #include <plib/ssg.h> // plib include
39 #include <simgear/compiler.h>
40 #include <simgear/misc/sg_path.hxx>
44 #include <simgear/scene/sky/cloud.hxx>
45 #include <simgear/scene/sky/dome.hxx>
46 #include <simgear/scene/sky/moon.hxx>
47 #include <simgear/scene/sky/oursun.hxx>
48 #include <simgear/scene/sky/stars.hxx>
53 typedef vector < SGCloudLayer* > layer_list_type;
54 typedef layer_list_type::iterator layer_list_iterator;
55 typedef layer_list_type::const_iterator layer_list_const_iterator;
58 float *view_pos, *zero_elev, *view_up;
59 double lon, lat, alt, spin;
61 double sun_ra, sun_dec, sun_dist;
62 double moon_ra, moon_dec, moon_dist;
66 float *sky_color, *fog_color, *cloud_color;
67 double sun_angle, moon_angle;
69 sgdVec3 *planet_data, *star_data;
73 * A class to model a realistic (time/date/position) based sky.
77 * The SGSky class models a blended sky dome, a haloed sun, a textured
78 * moon with phase that properly matches the date, stars and planets,
79 * and cloud layers. SGSky is designed to be dropped into existing
80 * plib based applications and depends heavily on plib's scene graph
81 * library, ssg. The sky implements various time of day lighting
82 * effects, it plays well with fog and visibility effects, and
83 * implements scudded cloud fly-through effects. Additionally, you can
84 * wire in the output of the SGEphemeris class to accurately position
85 * all the objects in the sky.
90 * Once you have created an instance of SGSky you must call the
91 * build() method. Building the sky requires several textures. So,
92 * you must specify the path/directory where these textures reside
93 * before building the sky. You do this first by calling the
94 * texture_path() method.
96 * The arguments you pass to the build() method allow you to specify
97 * the horizontal and vertical radiuses of the sky dome, the size of
98 * your sun sphere and moon sphere, a number of planets, and a
99 * multitude of stars. For the planets and stars you pass in an array
100 * of right ascensions, declinations, and magnitudes.
104 * Cloud layers can be added, changed, or removed individually. To add
105 * a cloud layer use the add_cloud_layer() method. The arguments
106 * allow you to specify base height above sea level, layer thickness,
107 * a transition zone for entering/leaving the cloud layer, the size of
108 * the cloud object, and the type of cloud texture. All distances are
109 * in meters. There are additional forms of this method that allow you
110 * to specify your own ssgSimpleState or texture name for drawing the
115 * As the sun circles the globe, you can call the repaint() method to
116 * recolor the sky objects to simulate sunrise and sunset effects,
117 * visibility, and other lighting changes. The arguments allow you to
118 * specify a base sky color (for the top of the dome), a fog color
119 * (for the horizon), the sun angle with the horizon (for
120 * sunrise/sunset effects), the moon angle (so we can make it more
121 * yellow at the horizon), and new star and planet data so that we can
122 * optionally change the magnitude of these (for day / night
125 * Positioning Sky Objects
127 * As time progresses and as you move across the surface of the earth,
128 * the apparent position of the objects and the various lighting
129 * effects can change. the reposition() method allows you to specify
130 * the positions of all the sky objects as well as your view position.
131 * The arguments allow you to specify your view position in world
132 * Cartesian coordinates, the zero elevation position in world
133 * Cartesian coordinates (your longitude, your latitude, sea level),
134 * the ``up'' vector in world Cartesian coordinates, current
135 * longitude, latitude, and altitude. A ``spin'' angle can be
136 * specified for orienting the sky with the sun position so sunset and
137 * sunrise effects look correct. You must specify GMT side real time,
138 * the sun right ascension, sun declination, and sun distance from
139 * view point (to keep it inside your view volume.) You also must
140 * specify moon right ascension, moon declination, and moon distance
145 * The sky is designed to be rendered in three stages. The first stage
146 * renders the parts that form your back drop - the sky dome, the
147 * stars and planets, the sun, and the moon. These should be rendered
148 * before the rest of your scene by calling the preDraw() method. The
149 * second stage renders the clouds that are above the viewer. This stage
150 * is done before translucent objects in the main scene are drawn. It
151 * is seperated from the preDraw routine to enable to implement a
152 * multi passes technique and is located in the drawUpperClouds() method.
153 * The third stage renders the clouds that are below the viewer an which
154 * are likely to be translucent (depending on type) and should be drawn
155 * after your scene has been rendered. Use the drawLowerClouds() method
156 * to draw the second stage of the sky.
158 * A typical application might do the following:
160 * <li> thesky->preDraw( my_altitude );
161 * <li> thesky->drawUpperClouds();
162 * <li> ssgCullAndDraw ( myscene ) ;
163 * <li> thesky->drawLowerClouds();
165 * The current altitude in meters is passed to the preDraw() method
166 * so the clouds layers can be rendered correction from most distant
171 * Visibility and fog is important for correctly rendering the
172 * sky. You can inform SGSky of the current visibility by calling the
173 * set_visibility() method.
175 * When transitioning through clouds, it is nice to pull in the fog as
176 * you get close to the cloud layer to hide the fact that the clouds
177 * are drawn as a flat polygon. As you get nearer to the cloud layer
178 * it is also nice to temporarily pull in the visibility to simulate
179 * the effects of flying in and out of the puffy edge of the
180 * cloud. These effects can all be accomplished by calling the
181 * modify_vis() method. The arguments allow you to specify your
182 * current altitude (which is then compared to the altitudes of the
183 * various cloud layers.) You can also specify a time factor which
184 * should be the length in seconds since the last time you called
185 * modify_vis(). The time_factor value allows the puffy cloud effect
186 * to be calculated correctly.
188 * The modify_vis() method alters the SGSky's internal idea of
189 * visibility, so you should subsequently call get_visibility() to get
190 * the actual modified visibility. You should then make the
191 * appropriate glFog() calls to setup fog properly for your scene.
195 * Once an instance of SGSky has been successfully initialized, there
196 * are a couple accessor methods you can use such as get_num_layers()
197 * to return the number of cloud layers, get_cloud_layer(i) to return
198 * cloud layer number i, get_visibility() to return the actual
199 * visibility as modified by the sky/cloud model.
207 // components of the sky
213 layer_list_type cloud_layers;
215 ssgRoot *pre_root, *post_root;
217 ssgSelector *pre_selector, *post_selector;
218 ssgTransform *pre_transform, *post_transform;
224 float effective_visibility;
229 // near cloud visibility state variables
231 double puff_length; // in seconds
232 double puff_progression; // in seconds
233 double ramp_up; // in seconds
234 double ramp_down; // in seconds
245 * Initialize the sky and connect the components to the scene
246 * graph at the provided branch. See discussion in detailed class
248 * @param h_radius_m horizontal radius of sky dome
249 * @param v_radius_m vertical radius of sky dome
250 * @param sun_size size of sun
251 * @param moon_size size of moon
252 * @param nplanets number of planets
253 * @param planet_data an array of planet right ascensions, declinations,
255 * @param nstars number of stars
256 * @param star_data an array of star right ascensions, declinations,
259 void build( double h_radius_m, double v_radius_m,
260 double sun_size, double moon_size,
261 int nplanets, sgdVec3 *planet_data,
262 int nstars, sgdVec3 *star_data );
265 * Repaint the sky components based on current value of sun_angle,
266 * sky, and fog colors. You can also specify new star and planet
267 * data so that we can optionally change the magnitude of these
268 * (for day/night transitions.) See discussion in detailed
271 * Sun and moon angles are specified in degrees relative to local up
272 * <li> 0 degrees = high noon
273 * <li> 90 degrees = sun rise/set
274 * <li> 180 degrees = darkest midnight
275 * @param sky_color the base sky color (for the top of the dome)
276 * @param fog_color the fog color (for the horizon)
277 * @param sun_angle the sun angle with the horizon (for sunrise/sunset
279 * @param moon_angle the moon angle (so we can make it more yellow
281 * @param nplanets number of planets
282 * @param planet_data an array of planet right ascensions, declinations,
284 * @param nstars number of stars
285 * @param star_data an array of star right ascensions, declinations,
288 bool repaint( const SGSkyColor &sc );
291 * Reposition the sky at the specified origin and orientation
293 * lon specifies a rotation about the Z axis
294 * lat specifies a rotation about the new Y axis
295 * spin specifies a rotation about the new Z axis (this allows
296 * additional orientation for the sunrise/set effects and is used
297 * by the skydome and perhaps clouds. See discussion in detailed
299 * @param view_pos specify your view position in world Cartesian
301 * @param zero_elev the zero elevation position in world Cartesian
303 * @param view_up the up vector in world Cartesian coordinates
304 * @param lon current longitude
305 * @param lat current latitude
306 * @param alt current altitude
307 * @param spin an offset angle for orienting the sky effects with the
308 * sun position so sunset and sunrise effects look correct.
309 * @param gst GMT side real time
310 * @param sun_ra the sun's current right ascension
311 * @param sun_dec the sun's current declination
312 * @param sun_dist the sun's distance from the current view point
313 * (to keep it inside your view volume.)
314 * @param moon_ra the moon's current right ascension
315 * @param moon_dec the moon's current declination
316 * @param moon_dist the moon's distance from the current view point.
318 bool reposition( SGSkyState &st, double dt = 0.0 );
321 * Modify the given visibility based on cloud layers, thickness,
322 * transition range, and simulated "puffs". See discussion in detailed
324 * @param alt current altitude
325 * @param time_factor amount of time since modify_vis() last called so
326 * we can scale effect rates properly despite variable frame rates.
328 void modify_vis( float alt, float time_factor );
331 * Draw background portions of the sky ... do this before you draw
332 * the rest of your scene. See discussion in detailed
334 * @param alt current altitude
336 void preDraw( float alt, float fog_exp2_density );
339 * Draw upper translucent clouds ... do this before you've drawn
340 * all the translucent elements of your scene. See discussion in
341 * detailed class description.
342 * @param fog_exp2_density fog density of the current cloud layer
344 void drawUpperClouds();
347 * Draw lower translucent clouds ... do this after you've drawn
348 * all the opaque elements of your scene. See discussion in detailed
351 void drawLowerClouds();
354 * Specify the texture path (optional, defaults to current directory)
355 * @param path base path to texture locations
357 inline void texture_path( const string& path ) {
358 tex_path = SGPath( path );
361 /** Enable drawing of the sky. */
362 inline void enable() {
363 pre_selector->select( 1 );
364 post_selector->select( 1 );
368 * Disable drawing of the sky in the scene graph. The leaf node is still
369 * there, how ever it won't be traversed on by ssgCullandRender()
371 inline void disable() {
372 pre_selector->select( 0 );
373 post_selector->select( 0 );
378 * Get the current sun color
380 inline float *get_sun_color() { return oursun->get_color(); }
383 * Get the sun halo texture handle
385 inline GLuint get_sun_texture_id() { return oursun->get_texture_id(); }
391 * Transfer pointer ownership to this object.
393 * @param layer The new cloud layer to add.
395 void add_cloud_layer (SGCloudLayer * layer);
399 * Get a cloud layer (const).
401 * Pointer ownership remains with this object.
403 * @param i The index of the cloud layer, zero-based.
404 * @return A const pointer to the cloud layer.
406 const SGCloudLayer * get_cloud_layer (int i) const;
410 * Get a cloud layer (non-const).
412 * Pointer ownership remains with this object.
414 * @param i The index of the cloud layer, zero-based.
415 * @return A non-const pointer to the cloud layer.
417 SGCloudLayer * get_cloud_layer (int i);
421 * Return the number of cloud layers currently available.
423 * @return The cloud layer count.
425 int get_cloud_layer_count () const;
428 /** @return current effective visibility */
429 inline float get_visibility() const { return effective_visibility; }
431 /** Set desired clear air visibility.
432 * @param v visibility in meters
434 inline void set_visibility( float v ) {
435 effective_visibility = visibility = (v <= 25.0) ? 25.0 : v;
440 #endif // _SG_SKY_HXX