Lazy tile splitting

[grits] / src / objects / gis-tile.c

diff --git a/src/objects/gis-tile.c b/src/objects/gis-tile.c
index fe3ff6ed8d3b2db94f0814620400b4baf949a62b..9a2a29886a4277ad90b2a503948dbf90a592c72d 100644 (file)
--- a/src/objects/gis-tile.c
+++ b/src/objects/gis-tile.c
@@ -93,13 +93,14 @@ gchar *gis_tile_get_path(GisTile *child)
        return g_string_free(path, FALSE);
 }
 
-static gdouble _gis_tile_get_min_dist(GisTile *tile,
-               gdouble lat, gdouble lon, gdouble elev)
+static gdouble _gis_tile_get_min_dist(
+               gdouble lat, gdouble lon, gdouble elev,
+               gdouble n, gdouble s, gdouble e, gdouble w)
 {
-       gdouble tlat  = lat > tile->edge.n ? tile->edge.n :
-                        lat < tile->edge.s ? tile->edge.s : lat;
-       gdouble tlon  = lon > tile->edge.e ? tile->edge.e :
-                       lon < tile->edge.w ? tile->edge.w : lon;
+       gdouble tlat  = lat > n ? n :
+                       lat < s ? s : lat;
+       gdouble tlon  = lon > e ? e :
+                       lon < w ? w : lon;
        gdouble telev = 0; // TODO: elevation at rlat,rlon
        //if (lat == tlat && lon == tlon)
        //      return elev; /* Shortcut? */
@@ -109,21 +110,23 @@ static gdouble _gis_tile_get_min_dist(GisTile *tile,
        return distd(a, b);
 }
 
-static gboolean _gis_tile_needs_split(GisTile *tile,
-               gdouble max_res, gint width, gint height,
-               gdouble lat, gdouble lon, gdouble elev)
+static gboolean _gis_tile_precise(
+               gdouble lat, gdouble lon, gdouble elev,
+               gdouble n, gdouble s, gdouble e, gdouble w,
+               gdouble max_res, gint width, gint height)
 {
-       gdouble lat_point = tile->edge.n < 0 ? tile->edge.n :
-                           tile->edge.s > 0 ? tile->edge.s : 0;
-       gdouble min_dist  = _gis_tile_get_min_dist(tile, lat, lon, elev);
+       gdouble min_dist  = _gis_tile_get_min_dist(lat, lon, elev, n, s, e, w);
        gdouble view_res  = MPPX(min_dist);
-       gdouble lon_dist  = tile->edge.e - tile->edge.w;
+
+       gdouble lat_point = n < 0 ? n : s > 0 ? s : 0;
+       gdouble lon_dist  = e - w;
        gdouble tile_res  = ll2m(lon_dist, lat_point)/width;
 
        /* This isn't really right, but it helps with memory since we don't (yet?) test if the tile
         * would be drawn */
        gdouble scale = elev / min_dist;
        view_res /= scale;
+       //view_res /= 1.4; /* make it a little nicer, not sure why this is needed */
        //g_message("tile=(%7.2f %7.2f %7.2f %7.2f) "
        //          "eye=(%9.1f %9.1f %9.1f) "
        //          "elev=%9.1f / dist=%9.1f = %f",
@@ -131,9 +134,8 @@ static gboolean _gis_tile_needs_split(GisTile *tile,
        //              lat, lon, elev,
        //              elev, min_dist, scale);
 
-       if (tile_res < max_res)
-               return FALSE;
-       return view_res < tile_res;
+       return tile_res < max_res ||
+              tile_res < view_res;
 }
 
 /**
@@ -160,23 +162,28 @@ void gis_tile_update(GisTile *root,
                GisTileLoadFunc load_func, gpointer user_data)
 {
        root->atime = time(NULL);
-       //g_debug("GisTile: update - %p->atime = %u", root, (guint)root->atime);
-       gdouble lat_dist = root->edge.n - root->edge.s;
-       gdouble lon_dist = root->edge.e - root->edge.w;
-       if (_gis_tile_needs_split(root, res, width, height, lat, lon, elev)) {
-               gdouble lat_step = lat_dist / G_N_ELEMENTS(root->children);
-               gdouble lon_step = lon_dist / G_N_ELEMENTS(root->children[0]);
-               int x, y;
-               gis_tile_foreach_index(root, x, y) {
-                       if (!root->children[x][y]) {
-                               root->children[x][y] = gis_tile_new(root,
-                                               root->edge.n-(lat_step*(x+0)),
-                                               root->edge.n-(lat_step*(x+1)),
-                                               root->edge.w+(lon_step*(y+1)),
-                                               root->edge.w+(lon_step*(y+0)));
-                               load_func(root->children[x][y], user_data);
+       //g_debug("GisTile: update - %p->atime = %u",
+       //              root, (guint)root->atime);
+       const gdouble rows = G_N_ELEMENTS(root->children);
+       const gdouble cols = G_N_ELEMENTS(root->children[0]);
+       const gdouble lat_dist = root->edge.n - root->edge.s;
+       const gdouble lon_dist = root->edge.e - root->edge.w;
+       const gdouble lat_step = lat_dist / rows;
+       const gdouble lon_step = lon_dist / cols;
+       int row, col;
+       gis_tile_foreach_index(root, row, col) {
+               GisTile **child = &root->children[row][col];
+               const gdouble n = root->edge.n-(lat_step*(row+0));
+               const gdouble s = root->edge.n-(lat_step*(row+1));
+               const gdouble e = root->edge.w+(lon_step*(col+1));
+               const gdouble w = root->edge.w+(lon_step*(col+0));
+               if (!_gis_tile_precise(lat,lon,elev, n,s,e,w,
+                                       res,width/cols,height/rows)) {
+                       if (!*child) {
+                               *child = gis_tile_new(root, n,s,e,w);
+                               load_func(*child, user_data);
                        }
-                       gis_tile_update(root->children[x][y],
+                       gis_tile_update(*child,
                                        res, width, height,
                                        lat, lon, elev,
                                        load_func, user_data);