2 * Copyright (C) 2009 Andy Spencer <spenceal@rose-hulman.edu>
4 * This program is free software: you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation, either version 3 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 /* Tessellation, "finding intersecting triangles" */
19 /* http://research.microsoft.com/pubs/70307/tr-2006-81.pdf */
20 /* http://www.opengl.org/wiki/Alpha_Blending */
25 #include <gdk/gdkkeysyms.h>
27 #include <gtk/gtkgl.h>
31 #include "gis-opengl.h"
33 #include "gis-object.h"
36 #define FOV_DIST 2000.0
37 #define MPPX(dist) (4*dist/FOV_DIST)
44 static void _gis_opengl_begin(GisOpenGL *self)
46 g_assert(GIS_IS_OPENGL(self));
48 GdkGLContext *glcontext = gtk_widget_get_gl_context(GTK_WIDGET(self));
49 GdkGLDrawable *gldrawable = gtk_widget_get_gl_drawable(GTK_WIDGET(self));
51 if (!gdk_gl_drawable_gl_begin(gldrawable, glcontext))
52 g_assert_not_reached();
55 static void _gis_opengl_end(GisOpenGL *self)
57 g_assert(GIS_IS_OPENGL(self));
58 GdkGLDrawable *gldrawable = gtk_widget_get_gl_drawable(GTK_WIDGET(self));
59 gdk_gl_drawable_gl_end(gldrawable);
62 static void _set_visuals(GisOpenGL *self)
64 glMatrixMode(GL_MODELVIEW);
68 double lat, lon, elev, rx, ry, rz;
69 gis_viewer_get_location(GIS_VIEWER(self), &lat, &lon, &elev);
70 gis_viewer_get_rotation(GIS_VIEWER(self), &rx, &ry, &rz);
71 glRotatef(rx, 1, 0, 0);
72 glRotatef(rz, 0, 0, 1);
76 float light_ambient[] = {0.7f, 0.7f, 0.7f, 1.0f};
77 float light_diffuse[] = {2.0f, 2.0f, 2.0f, 1.0f};
79 float light_ambient[] = {0.2f, 0.2f, 0.2f, 1.0f};
80 float light_diffuse[] = {5.0f, 5.0f, 5.0f, 1.0f};
82 float light_position[] = {-13*EARTH_R, 1*EARTH_R, 3*EARTH_R, 1.0f};
83 glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
84 glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
85 glLightfv(GL_LIGHT0, GL_POSITION, light_position);
87 glEnable(GL_LIGHTING);
89 float material_ambient[] = {0.2, 0.2, 0.2, 1.0};
90 float material_diffuse[] = {0.8, 0.8, 0.8, 1.0};
91 float material_specular[] = {0.0, 0.0, 0.0, 1.0};
92 float material_emission[] = {0.0, 0.0, 0.0, 1.0};
93 glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, material_ambient);
94 glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, material_diffuse);
95 glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, material_specular);
96 glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, material_emission);
97 glDisable(GL_TEXTURE_2D);
98 glDisable(GL_COLOR_MATERIAL);
101 glTranslatef(0, 0, -elev2rad(elev));
102 glRotatef(lat, 1, 0, 0);
103 glRotatef(-lon, 0, 1, 0);
106 gdouble rg = MAX(0, 1-(elev/20000));
107 gdouble blue = MAX(0, 1-(elev/50000));
108 glClearColor(MIN(0.65,rg), MIN(0.65,rg), MIN(1,blue), 1.0f);
109 glColor4f(1, 1, 1, 1);
111 glDisable(GL_ALPHA_TEST);
113 glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
118 glEnable(GL_CULL_FACE);
122 glDepthFunc(GL_LEQUAL);
123 glEnable(GL_DEPTH_TEST);
125 glEnable(GL_LINE_SMOOTH);
127 glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
128 //glShadeModel(GL_FLAT);
130 roam_sphere_update_view(self->sphere);
134 /********************
136 ********************/
137 static void _draw_marker(GisOpenGL *self, GisMarker *marker)
139 GisPoint *point = gis_object_center(GIS_OBJECT(marker));
141 gis_viewer_project(GIS_VIEWER(self),
142 point->lat, point->lon, point->elev,
147 //g_debug("GisOpenGL: draw_marker - %s pz=%f ", marker->label, pz);
149 cairo_surface_t *surface = cairo_get_target(marker->cairo);
150 gdouble width = cairo_image_surface_get_width(surface);
151 gdouble height = cairo_image_surface_get_height(surface);
153 glMatrixMode(GL_PROJECTION); glLoadIdentity();
154 glMatrixMode(GL_MODELVIEW); glLoadIdentity();
155 glOrtho(0, GTK_WIDGET(self)->allocation.width,
156 0, GTK_WIDGET(self)->allocation.height, -1, 1);
157 glTranslated(px - marker->xoff,
158 py - marker->yoff, 0);
160 glDisable(GL_LIGHTING);
161 glDisable(GL_COLOR_MATERIAL);
162 glDisable(GL_DEPTH_TEST);
163 glEnable(GL_TEXTURE_2D);
164 glBindTexture(GL_TEXTURE_2D, marker->tex);
166 glTexCoord2f(1, 1); glVertex3f(width, 0 , 0);
167 glTexCoord2f(1, 0); glVertex3f(width, height, 0);
168 glTexCoord2f(0, 0); glVertex3f(0 , height, 0);
169 glTexCoord2f(0, 1); glVertex3f(0 , 0 , 0);
173 static void _draw_callback(GisOpenGL *self, GisCallback *callback)
175 callback->callback(callback, callback->user_data);
178 static void _draw_object(GisOpenGL *self, GisObject *object)
180 //g_debug("GisOpenGL: draw_object");
181 /* Skip out of range objects */
182 if (object->lod > 0) {
183 gdouble eye[3], obj[3];
184 gis_viewer_get_location(GIS_VIEWER(self), &eye[0], &eye[1], &eye[2]);
185 lle2xyz(eye[0], eye[1], eye[2], &eye[0], &eye[1], &eye[2]);
186 lle2xyz(object->center.lat, object->center.lon, object->center.elev,
187 &obj[0], &obj[1], &obj[2]);
188 gdouble dist = distd(obj, eye);
189 if (object->lod < dist)
194 glMatrixMode(GL_PROJECTION); glPushMatrix();
195 glMatrixMode(GL_MODELVIEW); glPushMatrix();
196 glPushAttrib(GL_ALL_ATTRIB_BITS);
197 switch (object->type) {
198 case GIS_TYPE_MARKER:
199 _draw_marker(self, GIS_MARKER(object));
201 case GIS_TYPE_CALLBACK:
202 _draw_callback(self, GIS_CALLBACK(object));
208 glMatrixMode(GL_PROJECTION); glPopMatrix();
209 glMatrixMode(GL_MODELVIEW); glPopMatrix();
212 static void _load_object(GisOpenGL *self, GisObject *object)
214 g_debug("GisOpenGL: load_object");
215 switch (object->type) {
216 case GIS_TYPE_MARKER: {
217 GisMarker *marker = GIS_MARKER(object);
218 cairo_surface_t *surface = cairo_get_target(marker->cairo);
219 gdouble width = cairo_image_surface_get_width(surface);
220 gdouble height = cairo_image_surface_get_height(surface);
222 _gis_opengl_begin(self);
223 glEnable(GL_TEXTURE_2D);
224 glGenTextures(1, &marker->tex);
225 glBindTexture(GL_TEXTURE_2D, marker->tex);
227 glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
228 glPixelStorei(GL_PACK_ALIGNMENT, 1);
229 glTexImage2D(GL_TEXTURE_2D, 0, 4, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE,
230 cairo_image_surface_get_data(surface));
231 glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
232 glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
233 g_debug("load_texture: %d", marker->tex);
234 _gis_opengl_end(self);
242 static void _unload_object(GisOpenGL *self, GisObject *object)
244 g_debug("GisOpenGL: unload_object");
245 switch (object->type) {
246 case GIS_TYPE_MARKER: {
247 GisMarker *marker = GIS_MARKER(object);
248 g_debug("delete_texture: %d", marker->tex);
249 glDeleteTextures(1, &marker->tex);
261 /* The unsorted/sroted GLists are blank head nodes,
262 * This way us we can remove objects from the level just by fixing up links
263 * I.e. we don't need to do a lookup to remove an object if we have its GList */
269 static void on_realize(GisOpenGL *self, gpointer _)
271 g_debug("GisOpenGL: on_realize");
273 roam_sphere_update_errors(self->sphere);
275 static gboolean on_configure(GisOpenGL *self, GdkEventConfigure *event, gpointer _)
277 g_debug("GisOpenGL: on_configure");
278 _gis_opengl_begin(self);
280 double width = GTK_WIDGET(self)->allocation.width;
281 double height = GTK_WIDGET(self)->allocation.height;
283 /* Setup OpenGL Window */
284 glViewport(0, 0, width, height);
285 glMatrixMode(GL_PROJECTION);
287 double ang = atan(height/FOV_DIST);
288 gluPerspective(rad2deg(ang)*2, width/height, 1, 10*EARTH_R);
291 roam_sphere_update_errors(self->sphere);
294 _gis_opengl_end(self);
298 static gboolean _draw_level(gpointer key, gpointer value, gpointer user_data)
300 g_debug("GisOpenGL: _draw_level - level=%-4d", (int)key);
301 GisOpenGL *self = user_data;
302 struct RenderLevel *level = value;
303 int nsorted = 0, nunsorted = 0;
306 /* Draw opaque objects without sorting */
308 glClear(GL_DEPTH_BUFFER_BIT);
309 for (cur = level->unsorted.next; cur; cur = cur->next, nunsorted++)
310 _draw_object(self, GIS_OBJECT(cur->data));
312 /* Freeze depth buffer and draw transparent objects sorted */
315 for (cur = level->sorted.next; cur; cur = cur->next, nsorted++)
316 _draw_object(self, GIS_OBJECT(cur->data));
318 /* TODO: Prune empty levels */
320 g_debug("GisOpenGL: _draw_level - drew %d,%d objects",
325 static gboolean on_expose(GisOpenGL *self, GdkEventExpose *event, gpointer _)
327 g_debug("GisOpenGL: on_expose - begin");
328 _gis_opengl_begin(self);
330 glClear(GL_COLOR_BUFFER_BIT);
334 glColor4f(0.0, 0.0, 9.0, 0.6);
335 glDisable(GL_TEXTURE_2D);
336 glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
337 roam_sphere_draw(self->sphere);
338 //roam_sphere_draw_normals(self->sphere);
340 g_tree_foreach(self->objects, _draw_level, self);
341 if (self->wireframe) {
342 glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
343 roam_sphere_draw(self->sphere);
347 GdkGLDrawable *gldrawable = gtk_widget_get_gl_drawable(GTK_WIDGET(self));
348 gdk_gl_drawable_swap_buffers(gldrawable);
350 _gis_opengl_end(self);
351 g_debug("GisOpenGL: on_expose - end\n");
355 static gboolean on_key_press(GisOpenGL *self, GdkEventKey *event, gpointer _)
357 g_debug("GisOpenGL: on_key_press - key=%x, state=%x, plus=%x",
358 event->keyval, event->state, GDK_plus);
360 guint kv = event->keyval;
364 self->wireframe = !self->wireframe;
365 gtk_widget_queue_draw(GTK_WIDGET(self));
368 else if (kv == GDK_n) roam_sphere_split_one(self->sphere);
369 else if (kv == GDK_p) roam_sphere_merge_one(self->sphere);
370 else if (kv == GDK_r) roam_sphere_split_merge(self->sphere);
371 else if (kv == GDK_u) roam_sphere_update_errors(self->sphere);
373 gtk_widget_queue_draw(GTK_WIDGET(self));
380 static gboolean _update_errors_cb(gpointer sphere)
382 roam_sphere_update_errors(sphere);
385 static void on_view_changed(GisOpenGL *self,
386 gdouble _1, gdouble _2, gdouble _3)
388 g_debug("GisOpenGL: on_view_changed");
390 _gis_opengl_begin(self);
393 g_idle_add_full(G_PRIORITY_HIGH_IDLE+30, _update_errors_cb, self->sphere, NULL);
394 //roam_sphere_update_errors(self->sphere);
396 _gis_opengl_end(self);
400 static gboolean on_idle(GisOpenGL *self)
402 //g_debug("GisOpenGL: on_idle");
404 _gis_opengl_begin(self);
405 if (roam_sphere_split_merge(self->sphere))
406 gtk_widget_queue_draw(GTK_WIDGET(self));
407 _gis_opengl_end(self);
413 /*********************
414 * GisViewer methods *
415 *********************/
416 GisViewer *gis_opengl_new(GisPlugins *plugins)
418 g_debug("GisOpenGL: new");
419 GisViewer *self = g_object_new(GIS_TYPE_OPENGL, NULL);
420 self->plugins = plugins;
424 static void gis_opengl_center_position(GisViewer *_self, gdouble lat, gdouble lon, gdouble elev)
426 GisOpenGL *self = GIS_OPENGL(_self);
427 glRotatef(lon, 0, 1, 0);
428 glRotatef(-lat, 1, 0, 0);
429 glTranslatef(0, 0, elev2rad(elev));
432 static void gis_opengl_project(GisViewer *_self,
433 gdouble lat, gdouble lon, gdouble elev,
434 gdouble *px, gdouble *py, gdouble *pz)
436 GisOpenGL *self = GIS_OPENGL(_self);
438 lle2xyz(lat, lon, elev, &x, &y, &z);
440 self->sphere->view->model,
441 self->sphere->view->proj,
442 self->sphere->view->view,
446 static void gis_opengl_render_tile(GisViewer *_self, GisTile *tile)
448 GisOpenGL *self = GIS_OPENGL(_self);
449 if (!tile || !tile->data)
451 GList *triangles = roam_sphere_get_intersect(self->sphere, FALSE,
452 tile->edge.n, tile->edge.s, tile->edge.e, tile->edge.w);
454 g_warning("GisOpenGL: render_tiles - No triangles to draw: edges=%f,%f,%f,%f",
455 tile->edge.n, tile->edge.s, tile->edge.e, tile->edge.w);
456 //g_message("rendering %4d triangles for tile edges=%7.2f,%7.2f,%7.2f,%7.2f",
457 // g_list_length(triangles), tile->edge.n, tile->edge.s, tile->edge.e, tile->edge.w);
458 for (GList *cur = triangles; cur; cur = cur->next) {
459 RoamTriangle *tri = cur->data;
461 gdouble lat[3] = {tri->p.r->lat, tri->p.m->lat, tri->p.l->lat};
462 gdouble lon[3] = {tri->p.r->lon, tri->p.m->lon, tri->p.l->lon};
464 if (lon[0] < -90 || lon[1] < -90 || lon[2] < -90) {
465 if (lon[0] > 90) lon[0] -= 360;
466 if (lon[1] > 90) lon[1] -= 360;
467 if (lon[2] > 90) lon[2] -= 360;
470 gdouble n = tile->edge.n;
471 gdouble s = tile->edge.s;
472 gdouble e = tile->edge.e;
473 gdouble w = tile->edge.w;
475 gdouble londist = e - w;
476 gdouble latdist = n - s;
479 {(lon[0]-w)/londist, 1-(lat[0]-s)/latdist},
480 {(lon[1]-w)/londist, 1-(lat[1]-s)/latdist},
481 {(lon[2]-w)/londist, 1-(lat[2]-s)/latdist},
484 glEnable(GL_TEXTURE_2D);
485 glBindTexture(GL_TEXTURE_2D, *(guint*)tile->data);
486 glBegin(GL_TRIANGLES);
487 glNormal3dv(tri->p.r->norm); glTexCoord2dv(xy[0]); glVertex3dv((double*)tri->p.r);
488 glNormal3dv(tri->p.m->norm); glTexCoord2dv(xy[1]); glVertex3dv((double*)tri->p.m);
489 glNormal3dv(tri->p.l->norm); glTexCoord2dv(xy[2]); glVertex3dv((double*)tri->p.l);
492 g_list_free(triangles);
495 static void gis_opengl_render_tiles(GisViewer *_self, GisTile *tile)
497 GisOpenGL *self = GIS_OPENGL(_self);
498 /* Only render children if possible */
499 gboolean has_children = TRUE;
501 gis_tile_foreach(tile, child)
502 if (!child || !child->data)
503 has_children = FALSE;
505 /* Only render children */
506 gis_tile_foreach(tile, child)
507 gis_opengl_render_tiles(_self, child);
509 /* No children, render this tile */
510 gis_opengl_render_tile(_self, tile);
513 static void gis_opengl_set_height_func(GisViewer *_self, GisTile *tile,
514 RoamHeightFunc height_func, gpointer user_data, gboolean update)
516 GisOpenGL *self = GIS_OPENGL(_self);
519 /* TODO: get points? */
520 GList *triangles = roam_sphere_get_intersect(self->sphere, TRUE,
521 tile->edge.n, tile->edge.s, tile->edge.e, tile->edge.w);
522 for (GList *cur = triangles; cur; cur = cur->next) {
523 RoamTriangle *tri = cur->data;
524 RoamPoint *points[] = {tri->p.l, tri->p.m, tri->p.r, tri->split};
525 for (int i = 0; i < G_N_ELEMENTS(points); i++) {
526 if (tile->edge.n >= points[i]->lat && points[i]->lat >= tile->edge.s &&
527 tile->edge.e >= points[i]->lon && points[i]->lon >= tile->edge.w) {
528 points[i]->height_func = height_func;
529 points[i]->height_data = user_data;
530 roam_point_update_height(points[i]);
534 g_list_free(triangles);
537 static void _gis_opengl_clear_height_func_rec(RoamTriangle *root)
541 RoamPoint *points[] = {root->p.l, root->p.m, root->p.r, root->split};
542 for (int i = 0; i < G_N_ELEMENTS(points); i++) {
543 points[i]->height_func = NULL;
544 points[i]->height_data = NULL;
545 roam_point_update_height(points[i]);
547 _gis_opengl_clear_height_func_rec(root->kids[0]);
548 _gis_opengl_clear_height_func_rec(root->kids[1]);
551 static void gis_opengl_clear_height_func(GisViewer *_self)
553 GisOpenGL *self = GIS_OPENGL(_self);
554 for (int i = 0; i < G_N_ELEMENTS(self->sphere->roots); i++)
555 _gis_opengl_clear_height_func_rec(self->sphere->roots[i]);
558 static void gis_opengl_begin(GisViewer *_self)
560 g_assert(GIS_IS_OPENGL(_self));
561 _gis_opengl_begin(GIS_OPENGL(_self));
564 static void gis_opengl_end(GisViewer *_self)
566 g_assert(GIS_IS_OPENGL(_self));
567 _gis_opengl_end(GIS_OPENGL(_self));
570 static gpointer gis_opengl_add(GisViewer *_self, GisObject *object,
571 gint key, gboolean sort)
573 g_assert(GIS_IS_OPENGL(_self));
574 GisOpenGL *self = GIS_OPENGL(_self);
575 _load_object(self, object);
576 struct RenderLevel *level = g_tree_lookup(self->objects, (gpointer)key);
578 level = g_new0(struct RenderLevel, 1);
579 g_tree_insert(self->objects, (gpointer)key, level);
581 GList *list = sort ? &level->sorted : &level->unsorted;
582 list->next = g_list_prepend(list->next, object);
586 static void gis_opengl_remove(GisViewer *_self, gpointer _link)
588 g_assert(GIS_IS_OPENGL(_self));
590 GisOpenGL *self = GIS_OPENGL(_self);
591 _unload_object(self, link->data);
592 /* Just unlink and free it (blowup link to avoid warnings) */
593 link = g_list_delete_link(NULL, link);
599 static int _objects_cmp(gconstpointer _a, gconstpointer _b)
601 gint a = (int)_a, b = (int)_b;
606 G_DEFINE_TYPE(GisOpenGL, gis_opengl, GIS_TYPE_VIEWER);
607 static void gis_opengl_init(GisOpenGL *self)
609 g_debug("GisOpenGL: init");
611 GdkGLConfig *glconfig = gdk_gl_config_new_by_mode(
612 GDK_GL_MODE_RGBA | GDK_GL_MODE_DEPTH |
613 GDK_GL_MODE_DOUBLE | GDK_GL_MODE_ALPHA);
615 g_error("Failed to create glconfig");
616 if (!gtk_widget_set_gl_capability(GTK_WIDGET(self),
617 glconfig, NULL, TRUE, GDK_GL_RGBA_TYPE))
618 g_error("GL lacks required capabilities");
619 g_object_unref(glconfig);
621 gtk_widget_set_size_request(GTK_WIDGET(self), 600, 550);
622 gtk_widget_set_events(GTK_WIDGET(self),
623 GDK_BUTTON_PRESS_MASK |
624 GDK_ENTER_NOTIFY_MASK |
626 g_object_set(self, "can-focus", TRUE, NULL);
628 self->objects = g_tree_new(_objects_cmp);
629 self->sphere = roam_sphere_new(self);
632 self->sm_source[0] = g_timeout_add_full(G_PRIORITY_HIGH_IDLE+30, 33, (GSourceFunc)on_idle, self, NULL);
633 self->sm_source[1] = g_timeout_add_full(G_PRIORITY_HIGH_IDLE+10, 500, (GSourceFunc)on_idle, self, NULL);
636 g_signal_connect(self, "realize", G_CALLBACK(on_realize), NULL);
637 g_signal_connect(self, "configure-event", G_CALLBACK(on_configure), NULL);
638 g_signal_connect(self, "expose-event", G_CALLBACK(on_expose), NULL);
640 g_signal_connect(self, "key-press-event", G_CALLBACK(on_key_press), NULL);
642 g_signal_connect(self, "location-changed", G_CALLBACK(on_view_changed), NULL);
643 g_signal_connect(self, "rotation-changed", G_CALLBACK(on_view_changed), NULL);
645 static void gis_opengl_dispose(GObject *_self)
647 g_debug("GisOpenGL: dispose");
648 GisOpenGL *self = GIS_OPENGL(_self);
649 if (self->sm_source[0]) {
650 g_source_remove(self->sm_source[0]);
651 self->sm_source[0] = 0;
653 if (self->sm_source[1]) {
654 g_source_remove(self->sm_source[1]);
655 self->sm_source[1] = 0;
658 roam_sphere_free(self->sphere);
661 /* TODO: Cleanup/free objects tree */
662 G_OBJECT_CLASS(gis_opengl_parent_class)->dispose(_self);
664 static void gis_opengl_finalize(GObject *_self)
666 g_debug("GisViewer: finalize");
667 GisOpenGL *self = GIS_OPENGL(_self);
668 G_OBJECT_CLASS(gis_opengl_parent_class)->finalize(_self);
670 static void gis_opengl_class_init(GisOpenGLClass *klass)
672 g_debug("GisOpenGL: class_init");
673 GObjectClass *gobject_class = G_OBJECT_CLASS(klass);
674 gobject_class->dispose = gis_opengl_dispose;
676 GisViewerClass *viewer_class = GIS_VIEWER_CLASS(klass);
677 viewer_class->center_position = gis_opengl_center_position;
678 viewer_class->project = gis_opengl_project;
679 viewer_class->clear_height_func = gis_opengl_clear_height_func;
680 viewer_class->set_height_func = gis_opengl_set_height_func;
681 viewer_class->render_tile = gis_opengl_render_tile;
682 viewer_class->render_tiles = gis_opengl_render_tiles;
683 viewer_class->begin = gis_opengl_begin;
684 viewer_class->end = gis_opengl_end;
685 viewer_class->add = gis_opengl_add;
686 viewer_class->remove = gis_opengl_remove;