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 Library General Public
22 // License along with this library; if not, write to the
23 // Free Software Foundation, Inc., 59 Temple Place - Suite 330,
24 // Boston, MA 02111-1307, USA.
34 # error This library requires C++
38 #include <plib/ssg.h> // plib include
40 #include <simgear/compiler.h>
41 #include <simgear/misc/sg_path.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;
67 float *sky_color, *fog_color, *cloud_color;
68 double sun_angle, moon_angle;
70 sgdVec3 *planet_data, *star_data;
74 * A class to model a realistic (time/date/position) based sky.
78 * The SGSky class models a blended sky dome, a haloed sun, a textured
79 * moon with phase that properly matches the date, stars and planets,
80 * and cloud layers. SGSky is designed to be dropped into existing
81 * plib based applications and depends heavily on plib's scene graph
82 * library, ssg. The sky implements various time of day lighting
83 * effects, it plays well with fog and visibility effects, and
84 * implements scudded cloud fly-through effects. Additionally, you can
85 * wire in the output of the SGEphemeris class to accurately position
86 * all the objects in the sky.
91 * Once you have created an instance of SGSky you must call the
92 * build() method. Building the sky requires several textures. So,
93 * you must specify the path/directory where these textures reside
94 * before building the sky. You do this first by calling the
95 * texture_path() method.
97 * The arguments you pass to the build() method allow you to specify
98 * the horizontal and vertical radiuses of the sky dome, the size of
99 * your sun sphere and moon sphere, a number of planets, and a
100 * multitude of stars. For the planets and stars you pass in an array
101 * of right ascensions, declinations, and magnitudes.
105 * Cloud layers can be added, changed, or removed individually. To add
106 * a cloud layer use the add_cloud_layer() method. The arguments
107 * allow you to specify base height above sea level, layer thickness,
108 * a transition zone for entering/leaving the cloud layer, the size of
109 * the cloud object, and the type of cloud texture. All distances are
110 * in meters. There are additional forms of this method that allow you
111 * to specify your own ssgSimpleState or texture name for drawing the
116 * As the sun circles the globe, you can call the repaint() method to
117 * recolor the sky objects to simulate sunrise and sunset effects,
118 * visibility, and other lighting changes. The arguments allow you to
119 * specify a base sky color (for the top of the dome), a fog color
120 * (for the horizon), the sun angle with the horizon (for
121 * sunrise/sunset effects), the moon angle (so we can make it more
122 * yellow at the horizon), and new star and planet data so that we can
123 * optionally change the magnitude of these (for day / night
126 * Positioning Sky Objects
128 * As time progresses and as you move across the surface of the earth,
129 * the apparent position of the objects and the various lighting
130 * effects can change. the reposition() method allows you to specify
131 * the positions of all the sky objects as well as your view position.
132 * The arguments allow you to specify your view position in world
133 * Cartesian coordinates, the zero elevation position in world
134 * Cartesian coordinates (your longitude, your latitude, sea level),
135 * the ``up'' vector in world Cartesian coordinates, current
136 * longitude, latitude, and altitude. A ``spin'' angle can be
137 * specified for orienting the sky with the sun position so sunset and
138 * sunrise effects look correct. You must specify GMT side real time,
139 * the sun right ascension, sun declination, and sun distance from
140 * view point (to keep it inside your view volume.) You also must
141 * specify moon right ascension, moon declination, and moon distance
146 * The sky is designed to be rendered in three stages. The first stage
147 * renders the parts that form your back drop - the sky dome, the
148 * stars and planets, the sun, and the moon. These should be rendered
149 * before the rest of your scene by calling the preDraw() method. The
150 * second stage renders the clouds that are above the viewer. This stage
151 * is done before translucent objects in the main scene are drawn. It
152 * is seperated from the preDraw routine to enable to implement a
153 * multi passes technique and is located in the drawUpperClouds() method.
154 * The third stage renders the clouds that are below the viewer an which
155 * are likely to be translucent (depending on type) and should be drawn
156 * after your scene has been rendered. Use the drawLowerClouds() method
157 * to draw the second stage of the sky.
159 * A typical application might do the following:
161 * <li> thesky->preDraw( my_altitude );
162 * <li> thesky->drawUpperClouds();
163 * <li> ssgCullAndDraw ( myscene ) ;
164 * <li> thesky->drawLowerClouds();
166 * The current altitude in meters is passed to the preDraw() method
167 * so the clouds layers can be rendered correction from most distant
172 * Visibility and fog is important for correctly rendering the
173 * sky. You can inform SGSky of the current visibility by calling the
174 * set_visibility() method.
176 * When transitioning through clouds, it is nice to pull in the fog as
177 * you get close to the cloud layer to hide the fact that the clouds
178 * are drawn as a flat polygon. As you get nearer to the cloud layer
179 * it is also nice to temporarily pull in the visibility to simulate
180 * the effects of flying in and out of the puffy edge of the
181 * cloud. These effects can all be accomplished by calling the
182 * modify_vis() method. The arguments allow you to specify your
183 * current altitude (which is then compared to the altitudes of the
184 * various cloud layers.) You can also specify a time factor which
185 * should be the length in seconds since the last time you called
186 * modify_vis(). The time_factor value allows the puffy cloud effect
187 * to be calculated correctly.
189 * The modify_vis() method alters the SGSky's internal idea of
190 * visibility, so you should subsequently call get_visibility() to get
191 * the actual modified visibility. You should then make the
192 * appropriate glFog() calls to setup fog properly for your scene.
196 * Once an instance of SGSky has been successfully initialized, there
197 * are a couple accessor methods you can use such as get_num_layers()
198 * to return the number of cloud layers, get_cloud_layer(i) to return
199 * cloud layer number i, get_visibility() to return the actual
200 * visibility as modified by the sky/cloud model.
208 // components of the sky
214 layer_list_type cloud_layers;
216 ssgRoot *pre_root, *post_root;
218 ssgSelector *pre_selector, *post_selector;
219 ssgTransform *pre_transform, *post_transform;
225 float effective_visibility;
230 // near cloud visibility state variables
232 double puff_length; // in seconds
233 double puff_progression; // in seconds
234 double ramp_up; // in seconds
235 double ramp_down; // in seconds
246 * Initialize the sky and connect the components to the scene
247 * graph at the provided branch. See discussion in detailed class
249 * @param h_radius_m horizontal radius of sky dome
250 * @param v_radius_m vertical radius of sky dome
251 * @param sun_size size of sun
252 * @param moon_size size of moon
253 * @param nplanets number of planets
254 * @param planet_data an array of planet right ascensions, declinations,
256 * @param nstars number of stars
257 * @param star_data an array of star right ascensions, declinations,
260 void build( double h_radius_m, double v_radius_m,
261 double sun_size, double moon_size,
262 int nplanets, sgdVec3 *planet_data,
263 int nstars, sgdVec3 *star_data );
266 * Repaint the sky components based on current value of sun_angle,
267 * sky, and fog colors. You can also specify new star and planet
268 * data so that we can optionally change the magnitude of these
269 * (for day/night transitions.) See discussion in detailed
272 * Sun and moon angles are specified in degrees relative to local up
273 * <li> 0 degrees = high noon
274 * <li> 90 degrees = sun rise/set
275 * <li> 180 degrees = darkest midnight
276 * @param sky_color the base sky color (for the top of the dome)
277 * @param fog_color the fog color (for the horizon)
278 * @param sun_angle the sun angle with the horizon (for sunrise/sunset
280 * @param moon_angle the moon angle (so we can make it more yellow
282 * @param nplanets number of planets
283 * @param planet_data an array of planet right ascensions, declinations,
285 * @param nstars number of stars
286 * @param star_data an array of star right ascensions, declinations,
289 bool repaint( const SGSkyColor &sc );
292 * Reposition the sky at the specified origin and orientation
294 * lon specifies a rotation about the Z axis
295 * lat specifies a rotation about the new Y axis
296 * spin specifies a rotation about the new Z axis (this allows
297 * additional orientation for the sunrise/set effects and is used
298 * by the skydome and perhaps clouds. See discussion in detailed
300 * @param view_pos specify your view position in world Cartesian
302 * @param zero_elev the zero elevation position in world Cartesian
304 * @param view_up the up vector in world Cartesian coordinates
305 * @param lon current longitude
306 * @param lat current latitude
307 * @param alt current altitude
308 * @param spin an offset angle for orienting the sky effects with the
309 * sun position so sunset and sunrise effects look correct.
310 * @param gst GMT side real time
311 * @param sun_ra the sun's current right ascension
312 * @param sun_dec the sun's current declination
313 * @param sun_dist the sun's distance from the current view point
314 * (to keep it inside your view volume.)
315 * @param moon_ra the moon's current right ascension
316 * @param moon_dec the moon's current declination
317 * @param moon_dist the moon's distance from the current view point.
319 bool reposition( SGSkyState &st, double dt = 0.0 );
322 * Modify the given visibility based on cloud layers, thickness,
323 * transition range, and simulated "puffs". See discussion in detailed
325 * @param alt current altitude
326 * @param time_factor amount of time since modify_vis() last called so
327 * we can scale effect rates properly despite variable frame rates.
329 void modify_vis( float alt, float time_factor );
332 * Draw background portions of the sky ... do this before you draw
333 * the rest of your scene. See discussion in detailed
335 * @param alt current altitude
337 void preDraw( float alt, float fog_exp2_density );
340 * Draw upper translucent clouds ... do this before you've drawn
341 * all the translucent elements of your scene. See discussion in
342 * detailed class description.
343 * @param fog_exp2_density fog density of the current cloud layer
345 void drawUpperClouds();
348 * Draw lower translucent clouds ... do this after you've drawn
349 * all the opaque elements of your scene. See discussion in detailed
352 void drawLowerClouds();
355 * Specify the texture path (optional, defaults to current directory)
356 * @param path base path to texture locations
358 inline void texture_path( const string& path ) {
359 tex_path = SGPath( path );
362 /** Enable drawing of the sky. */
363 inline void enable() {
364 pre_selector->select( 1 );
365 post_selector->select( 1 );
369 * Disable drawing of the sky in the scene graph. The leaf node is still
370 * there, how ever it won't be traversed on by ssgCullandRender()
372 inline void disable() {
373 pre_selector->select( 0 );
374 post_selector->select( 0 );
379 * Get the current sun color
381 inline float *get_sun_color() { return oursun->get_color(); }
387 * Transfer pointer ownership to this object.
389 * @param layer The new cloud layer to add.
391 void add_cloud_layer (SGCloudLayer * layer);
395 * Get a cloud layer (const).
397 * Pointer ownership remains with this object.
399 * @param i The index of the cloud layer, zero-based.
400 * @return A const pointer to the cloud layer.
402 const SGCloudLayer * get_cloud_layer (int i) const;
406 * Get a cloud layer (non-const).
408 * Pointer ownership remains with this object.
410 * @param i The index of the cloud layer, zero-based.
411 * @return A non-const pointer to the cloud layer.
413 SGCloudLayer * get_cloud_layer (int i);
417 * Return the number of cloud layers currently available.
419 * @return The cloud layer count.
421 int get_cloud_layer_count () const;
424 /** @return current effective visibility */
425 inline float get_visibility() const { return effective_visibility; }
427 /** Set desired clear air visibility.
428 * @param v visibility in meters
430 inline void set_visibility( float v ) {
431 effective_visibility = visibility = (v <= 25.0) ? 25.0 : v;
436 #endif // _SG_SKY_HXX