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>
41 #include <simgear/props/props.hxx>
45 #include <simgear/scene/sky/cloud.hxx>
46 #include <simgear/scene/sky/dome.hxx>
47 #include <simgear/scene/sky/moon.hxx>
48 #include <simgear/scene/sky/oursun.hxx>
49 #include <simgear/scene/sky/stars.hxx>
54 typedef vector < SGCloudLayer* > layer_list_type;
55 typedef layer_list_type::iterator layer_list_iterator;
56 typedef layer_list_type::const_iterator layer_list_const_iterator;
59 float *view_pos, *zero_elev, *view_up;
60 double lon, lat, alt, spin;
62 double sun_ra, sun_dec, sun_dist;
63 double moon_ra, moon_dec, moon_dist;
68 float *sky_color, *fog_color, *cloud_color;
69 double sun_angle, moon_angle;
71 sgdVec3 *planet_data, *star_data;
75 * A class to model a realistic (time/date/position) based sky.
79 * The SGSky class models a blended sky dome, a haloed sun, a textured
80 * moon with phase that properly matches the date, stars and planets,
81 * and cloud layers. SGSky is designed to be dropped into existing
82 * plib based applications and depends heavily on plib's scene graph
83 * library, ssg. The sky implements various time of day lighting
84 * effects, it plays well with fog and visibility effects, and
85 * implements scudded cloud fly-through effects. Additionally, you can
86 * wire in the output of the SGEphemeris class to accurately position
87 * all the objects in the sky.
92 * Once you have created an instance of SGSky you must call the
93 * build() method. Building the sky requires several textures. So,
94 * you must specify the path/directory where these textures reside
95 * before building the sky. You do this first by calling the
96 * texture_path() method.
98 * The arguments you pass to the build() method allow you to specify
99 * the horizontal and vertical radiuses of the sky dome, the size of
100 * your sun sphere and moon sphere, a number of planets, and a
101 * multitude of stars. For the planets and stars you pass in an array
102 * of right ascensions, declinations, and magnitudes.
106 * Cloud layers can be added, changed, or removed individually. To add
107 * a cloud layer use the add_cloud_layer() method. The arguments
108 * allow you to specify base height above sea level, layer thickness,
109 * a transition zone for entering/leaving the cloud layer, the size of
110 * the cloud object, and the type of cloud texture. All distances are
111 * in meters. There are additional forms of this method that allow you
112 * to specify your own ssgSimpleState or texture name for drawing the
117 * As the sun circles the globe, you can call the repaint() method to
118 * recolor the sky objects to simulate sunrise and sunset effects,
119 * visibility, and other lighting changes. The arguments allow you to
120 * specify a base sky color (for the top of the dome), a fog color
121 * (for the horizon), the sun angle with the horizon (for
122 * sunrise/sunset effects), the moon angle (so we can make it more
123 * yellow at the horizon), and new star and planet data so that we can
124 * optionally change the magnitude of these (for day / night
127 * Positioning Sky Objects
129 * As time progresses and as you move across the surface of the earth,
130 * the apparent position of the objects and the various lighting
131 * effects can change. the reposition() method allows you to specify
132 * the positions of all the sky objects as well as your view position.
133 * The arguments allow you to specify your view position in world
134 * Cartesian coordinates, the zero elevation position in world
135 * Cartesian coordinates (your longitude, your latitude, sea level),
136 * the ``up'' vector in world Cartesian coordinates, current
137 * longitude, latitude, and altitude. A ``spin'' angle can be
138 * specified for orienting the sky with the sun position so sunset and
139 * sunrise effects look correct. You must specify GMT side real time,
140 * the sun right ascension, sun declination, and sun distance from
141 * view point (to keep it inside your view volume.) You also must
142 * specify moon right ascension, moon declination, and moon distance
147 * The sky is designed to be rendered in three stages. The first stage
148 * renders the parts that form your back drop - the sky dome, the
149 * stars and planets, the sun, and the moon. These should be rendered
150 * before the rest of your scene by calling the preDraw() method. The
151 * second stage renders the clouds that are above the viewer. This stage
152 * is done before translucent objects in the main scene are drawn. It
153 * is seperated from the preDraw routine to enable to implement a
154 * multi passes technique and is located in the drawUpperClouds() method.
155 * The third stage renders the clouds that are below the viewer an which
156 * are likely to be translucent (depending on type) and should be drawn
157 * after your scene has been rendered. Use the drawLowerClouds() method
158 * to draw the second stage of the sky.
160 * A typical application might do the following:
162 * <li> thesky->preDraw( my_altitude );
163 * <li> thesky->drawUpperClouds();
164 * <li> ssgCullAndDraw ( myscene ) ;
165 * <li> thesky->drawLowerClouds();
167 * The current altitude in meters is passed to the preDraw() method
168 * so the clouds layers can be rendered correction from most distant
173 * Visibility and fog is important for correctly rendering the
174 * sky. You can inform SGSky of the current visibility by calling the
175 * set_visibility() method.
177 * When transitioning through clouds, it is nice to pull in the fog as
178 * you get close to the cloud layer to hide the fact that the clouds
179 * are drawn as a flat polygon. As you get nearer to the cloud layer
180 * it is also nice to temporarily pull in the visibility to simulate
181 * the effects of flying in and out of the puffy edge of the
182 * cloud. These effects can all be accomplished by calling the
183 * modify_vis() method. The arguments allow you to specify your
184 * current altitude (which is then compared to the altitudes of the
185 * various cloud layers.) You can also specify a time factor which
186 * should be the length in seconds since the last time you called
187 * modify_vis(). The time_factor value allows the puffy cloud effect
188 * to be calculated correctly.
190 * The modify_vis() method alters the SGSky's internal idea of
191 * visibility, so you should subsequently call get_visibility() to get
192 * the actual modified visibility. You should then make the
193 * appropriate glFog() calls to setup fog properly for your scene.
197 * Once an instance of SGSky has been successfully initialized, there
198 * are a couple accessor methods you can use such as get_num_layers()
199 * to return the number of cloud layers, get_cloud_layer(i) to return
200 * cloud layer number i, get_visibility() to return the actual
201 * visibility as modified by the sky/cloud model.
209 // components of the sky
215 layer_list_type cloud_layers;
217 ssgRoot *pre_root, *post_root;
219 ssgSelector *pre_selector, *post_selector;
220 ssgTransform *pre_transform, *post_transform;
226 float effective_visibility;
231 // near cloud visibility state variables
233 double puff_length; // in seconds
234 double puff_progression; // in seconds
235 double ramp_up; // in seconds
236 double ramp_down; // in seconds
247 * Initialize the sky and connect the components to the scene
248 * graph at the provided branch. See discussion in detailed class
250 * @param h_radius_m horizontal radius of sky dome
251 * @param v_radius_m vertical radius of sky dome
252 * @param sun_size size of sun
253 * @param moon_size size of moon
254 * @param nplanets number of planets
255 * @param planet_data an array of planet right ascensions, declinations,
257 * @param nstars number of stars
258 * @param star_data an array of star right ascensions, declinations,
261 void build( double h_radius_m, double v_radius_m,
262 double sun_size, double moon_size,
263 int nplanets, sgdVec3 *planet_data,
264 int nstars, sgdVec3 *star_data, SGPropertyNode *property_tree_node );
267 * Repaint the sky components based on current value of sun_angle,
268 * sky, and fog colors. You can also specify new star and planet
269 * data so that we can optionally change the magnitude of these
270 * (for day/night transitions.) See discussion in detailed
273 * Sun and moon angles are specified in degrees relative to local up
274 * <li> 0 degrees = high noon
275 * <li> 90 degrees = sun rise/set
276 * <li> 180 degrees = darkest midnight
277 * @param sky_color the base sky color (for the top of the dome)
278 * @param fog_color the fog color (for the horizon)
279 * @param sun_angle the sun angle with the horizon (for sunrise/sunset
281 * @param moon_angle the moon angle (so we can make it more yellow
283 * @param nplanets number of planets
284 * @param planet_data an array of planet right ascensions, declinations,
286 * @param nstars number of stars
287 * @param star_data an array of star right ascensions, declinations,
290 bool repaint( const SGSkyColor &sc );
293 * Reposition the sky at the specified origin and orientation
295 * lon specifies a rotation about the Z axis
296 * lat specifies a rotation about the new Y axis
297 * spin specifies a rotation about the new Z axis (this allows
298 * additional orientation for the sunrise/set effects and is used
299 * by the skydome and perhaps clouds. See discussion in detailed
301 * @param view_pos specify your view position in world Cartesian
303 * @param zero_elev the zero elevation position in world Cartesian
305 * @param view_up the up vector in world Cartesian coordinates
306 * @param lon current longitude
307 * @param lat current latitude
308 * @param alt current altitude
309 * @param spin an offset angle for orienting the sky effects with the
310 * sun position so sunset and sunrise effects look correct.
311 * @param gst GMT side real time
312 * @param sun_ra the sun's current right ascension
313 * @param sun_dec the sun's current declination
314 * @param sun_dist the sun's distance from the current view point
315 * (to keep it inside your view volume.)
316 * @param moon_ra the moon's current right ascension
317 * @param moon_dec the moon's current declination
318 * @param moon_dist the moon's distance from the current view point.
320 bool reposition( SGSkyState &st, double dt = 0.0 );
323 * Modify the given visibility based on cloud layers, thickness,
324 * transition range, and simulated "puffs". See discussion in detailed
326 * @param alt current altitude
327 * @param time_factor amount of time since modify_vis() last called so
328 * we can scale effect rates properly despite variable frame rates.
330 void modify_vis( float alt, float time_factor );
333 * Draw background portions of the sky ... do this before you draw
334 * the rest of your scene. See discussion in detailed
336 * @param alt current altitude
338 void preDraw( float alt, float fog_exp2_density );
341 * Draw upper translucent clouds ... do this before you've drawn
342 * all the translucent elements of your scene. See discussion in
343 * detailed class description.
344 * @param fog_exp2_density fog density of the current cloud layer
346 void drawUpperClouds();
349 * Draw lower translucent clouds ... do this after you've drawn
350 * all the opaque elements of your scene. See discussion in detailed
353 void drawLowerClouds();
356 * Specify the texture path (optional, defaults to current directory)
357 * @param path base path to texture locations
359 inline void texture_path( const string& path ) {
360 tex_path = SGPath( path );
363 /** Enable drawing of the sky. */
364 inline void enable() {
365 pre_selector->select( 1 );
366 post_selector->select( 1 );
370 * Disable drawing of the sky in the scene graph. The leaf node is still
371 * there, how ever it won't be traversed on by ssgCullandRender()
373 inline void disable() {
374 pre_selector->select( 0 );
375 post_selector->select( 0 );
380 * Get the current sun color
382 inline float *get_sun_color() { return oursun->get_color(); }
385 * Get the sun halo texture handle
387 inline GLuint get_sun_texture_id() { return oursun->get_texture_id(); }
393 * Transfer pointer ownership to this object.
395 * @param layer The new cloud layer to add.
397 void add_cloud_layer (SGCloudLayer * layer);
401 * Get a cloud layer (const).
403 * Pointer ownership remains with this object.
405 * @param i The index of the cloud layer, zero-based.
406 * @return A const pointer to the cloud layer.
408 const SGCloudLayer * get_cloud_layer (int i) const;
412 * Get a cloud layer (non-const).
414 * Pointer ownership remains with this object.
416 * @param i The index of the cloud layer, zero-based.
417 * @return A non-const pointer to the cloud layer.
419 SGCloudLayer * get_cloud_layer (int i);
423 * Return the number of cloud layers currently available.
425 * @return The cloud layer count.
427 int get_cloud_layer_count () const;
430 /** @return current effective visibility */
431 inline float get_visibility() const { return effective_visibility; }
433 /** Set desired clear air visibility.
434 * @param v visibility in meters
436 inline void set_visibility( float v ) {
437 effective_visibility = visibility = (v <= 25.0) ? 25.0 : v;
442 #endif // _SG_SKY_HXX