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 - curt@flightgear.org
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 two 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 which are likely to be translucent
151 * (depending on type) and should be drawn after your scene has been
152 * rendered. Use the postDraw() method to draw the second stage of
155 * A typical application might do the following:
157 * <li> thesky->preDraw();
158 * <li> ssgCullAndDraw ( myscene ) ;
159 * <li> thesky->postDraw( my_altitude );
161 * The current altitude in meters is passed to the postDraw() method
162 * so the clouds layers can be rendered correction from most distant
167 * Visibility and fog is important for correctly rendering the
168 * sky. You can inform SGSky of the current visibility by calling the
169 * set_visibility() method.
171 * When transitioning through clouds, it is nice to pull in the fog as
172 * you get close to the cloud layer to hide the fact that the clouds
173 * are drawn as a flat polygon. As you get nearer to the cloud layer
174 * it is also nice to temporarily pull in the visibility to simulate
175 * the effects of flying in and out of the puffy edge of the
176 * cloud. These effects can all be accomplished by calling the
177 * modify_vis() method. The arguments allow you to specify your
178 * current altitude (which is then compared to the altitudes of the
179 * various cloud layers.) You can also specify a time factor which
180 * should be the length in seconds since the last time you called
181 * modify_vis(). The time_factor value allows the puffy cloud effect
182 * to be calculated correctly.
184 * The modify_vis() method alters the SGSky's internal idea of
185 * visibility, so you should subsequently call get_visibility() to get
186 * the actual modified visibility. You should then make the
187 * appropriate glFog() calls to setup fog properly for your scene.
191 * Once an instance of SGSky has been successfully initialized, there
192 * are a couple accessor methods you can use such as get_num_layers()
193 * to return the number of cloud layers, get_cloud_layer(i) to return
194 * cloud layer number i, get_visibility() to return the actual
195 * visibility as modified by the sky/cloud model.
203 // components of the sky
209 layer_list_type cloud_layers;
211 ssgRoot *pre_root, *post_root;
213 ssgSelector *pre_selector, *post_selector;
214 ssgTransform *pre_transform, *post_transform;
220 float effective_visibility;
225 // near cloud visibility state variables
227 double puff_length; // in seconds
228 double puff_progression; // in seconds
229 double ramp_up; // in seconds
230 double ramp_down; // in seconds
241 * Initialize the sky and connect the components to the scene
242 * graph at the provided branch. See discussion in detailed class
244 * @param h_radius_m horizontal radius of sky dome
245 * @param v_radius_m vertical radius of sky dome
246 * @param sun_size size of sun
247 * @param moon_size size of moon
248 * @param nplanets number of planets
249 * @param planet_data an array of planet right ascensions, declinations,
251 * @param nstars number of stars
252 * @param star_data an array of star right ascensions, declinations,
255 void build( double h_radius_m, double v_radius_m,
256 double sun_size, double moon_size,
257 int nplanets, sgdVec3 *planet_data,
258 int nstars, sgdVec3 *star_data );
261 * Repaint the sky components based on current value of sun_angle,
262 * sky, and fog colors. You can also specify new star and planet
263 * data so that we can optionally change the magnitude of these
264 * (for day/night transitions.) See discussion in detailed
267 * Sun and moon angles are specified in degrees relative to local up
268 * <li> 0 degrees = high noon
269 * <li> 90 degrees = sun rise/set
270 * <li> 180 degrees = darkest midnight
271 * @param sky_color the base sky color (for the top of the dome)
272 * @param fog_color the fog color (for the horizon)
273 * @param sun_angle the sun angle with the horizon (for sunrise/sunset
275 * @param moon_angle the moon angle (so we can make it more yellow
277 * @param nplanets number of planets
278 * @param planet_data an array of planet right ascensions, declinations,
280 * @param nstars number of stars
281 * @param star_data an array of star right ascensions, declinations,
284 bool repaint( const SGSkyColor &sc );
287 * Reposition the sky at the specified origin and orientation
289 * lon specifies a rotation about the Z axis
290 * lat specifies a rotation about the new Y axis
291 * spin specifies a rotation about the new Z axis (this allows
292 * additional orientation for the sunrise/set effects and is used
293 * by the skydome and perhaps clouds. See discussion in detailed
295 * @param view_pos specify your view position in world Cartesian
297 * @param zero_elev the zero elevation position in world Cartesian
299 * @param view_up the up vector in world Cartesian coordinates
300 * @param lon current longitude
301 * @param lat current latitude
302 * @param alt current altitude
303 * @param spin an offset angle for orienting the sky effects with the
304 * sun position so sunset and sunrise effects look correct.
305 * @param gst GMT side real time
306 * @param sun_ra the sun's current right ascension
307 * @param sun_dec the sun's current declination
308 * @param sun_dist the sun's distance from the current view point
309 * (to keep it inside your view volume.)
310 * @param moon_ra the moon's current right ascension
311 * @param moon_dec the moon's current declination
312 * @param moon_dist the moon's distance from the current view point.
314 bool reposition( SGSkyState &st, double dt = 0.0 );
317 * Modify the given visibility based on cloud layers, thickness,
318 * transition range, and simulated "puffs". See discussion in detailed
320 * @param alt current altitude
321 * @param time_factor amount of time since modify_vis() last called so
322 * we can scale effect rates properly despite variable frame rates.
324 void modify_vis( float alt, float time_factor );
327 * Draw background portions of the sky ... do this before you draw
328 * the rest of your scene. See discussion in detailed
330 * @param alt current altitude
332 void preDraw( float alt, float fog_exp2_density );
335 * Draw translucent clouds ... do this after you've drawn all the
336 * oapaque elements of your scene. See discussion in detailed
338 * @param alt current altitude
340 void postDraw( float alt );
343 * Specify the texture path (optional, defaults to current directory)
344 * @param path base path to texture locations
346 inline void texture_path( const string& path ) {
347 tex_path = SGPath( path );
350 /** Enable drawing of the sky. */
351 inline void enable() {
352 pre_selector->select( 1 );
353 post_selector->select( 1 );
357 * Disable drawing of the sky in the scene graph. The leaf node is still
358 * there, how ever it won't be traversed on by ssgCullandRender()
360 inline void disable() {
361 pre_selector->select( 0 );
362 post_selector->select( 0 );
367 * Get the current sun color
369 inline float *get_sun_color() { return oursun->get_color(); }
375 * Transfer pointer ownership to this object.
377 * @param layer The new cloud layer to add.
379 void add_cloud_layer (SGCloudLayer * layer);
383 * Get a cloud layer (const).
385 * Pointer ownership remains with this object.
387 * @param i The index of the cloud layer, zero-based.
388 * @return A const pointer to the cloud layer.
390 const SGCloudLayer * get_cloud_layer (int i) const;
394 * Get a cloud layer (non-const).
396 * Pointer ownership remains with this object.
398 * @param i The index of the cloud layer, zero-based.
399 * @return A non-const pointer to the cloud layer.
401 SGCloudLayer * get_cloud_layer (int i);
405 * Return the number of cloud layers currently available.
407 * @return The cloud layer count.
409 int get_cloud_layer_count () const;
412 /** @return current effective visibility */
413 inline float get_visibility() const { return effective_visibility; }
415 /** Set desired clear air visibility.
416 * @param v visibility in meters
418 inline void set_visibility( float v ) {
419 effective_visibility = visibility = (v <= 25.0) ? 25.0 : v;
424 #endif // _SG_SKY_HXX