public int compare(MercatorTextureTile ta, MercatorTextureTile tb) {
int la =
ta.getFallbackTile() == null
? ta.getLevelNumber()
: ta.getFallbackTile().getLevelNumber();
int lb =
tb.getFallbackTile() == null
? tb.getLevelNumber()
: tb.getFallbackTile().getLevelNumber();
return la < lb ? -1 : la == lb ? 0 : 1;
}
private void addTile(DrawContext dc, MercatorTextureTile tile) {
tile.setFallbackTile(null);
if (tile.isTextureInMemory(dc.getTextureCache())) {
// System.out.printf("Sector %s, min = %f, max = %f\n", tile.getSector(),
// dc.getGlobe().getMinElevation(tile.getSector()),
// dc.getGlobe().getMaxElevation(tile.getSector()));
this.addTileToCurrent(tile);
return;
}
// Level 0 loads may be forced
if (tile.getLevelNumber() == 0
&& this.forceLevelZeroLoads
&& !tile.isTextureInMemory(dc.getTextureCache())) {
this.forceTextureLoad(tile);
if (tile.isTextureInMemory(dc.getTextureCache())) {
this.addTileToCurrent(tile);
return;
}
}
// Tile's texture isn't available, so request it
if (tile.getLevelNumber() < this.levels.getNumLevels()) {
// Request only tiles with data associated at this level
if (!this.levels.isResourceAbsent(tile)) this.requestTexture(dc, tile);
}
// Set up to use the currentResource tile's texture
if (this.currentResourceTile != null) {
if (this.currentResourceTile.getLevelNumber() == 0
&& this.forceLevelZeroLoads
&& !this.currentResourceTile.isTextureInMemory(dc.getTextureCache())
&& !this.currentResourceTile.isTextureInMemory(dc.getTextureCache()))
this.forceTextureLoad(this.currentResourceTile);
if (this.currentResourceTile.isTextureInMemory(dc.getTextureCache())) {
tile.setFallbackTile(currentResourceTile);
this.addTileToCurrent(tile);
}
}
}
private boolean meetsRenderCriteria(DrawContext dc, MercatorTextureTile tile) {
return this.levels.isFinalLevel(tile.getLevelNumber()) || !needToSplit(dc, tile.getSector());
}
private void addTileOrDescendants(DrawContext dc, MercatorTextureTile tile) {
if (this.meetsRenderCriteria(dc, tile)) {
this.addTile(dc, tile);
return;
}
// The incoming tile does not meet the rendering criteria, so it must be subdivided and those
// subdivisions tested against the criteria.
// All tiles that meet the selection criteria are drawn, but some of those tiles will not have
// textures associated with them either because their texture isn't loaded yet or because they
// are finer grain than the layer has textures for. In these cases the tiles use the texture of
// the closest ancestor that has a texture loaded. This ancestor is called the
// currentResourceTile.
// A texture transform is applied during rendering to align the sector's texture coordinates
// with the
// appropriate region of the ancestor's texture.
MercatorTextureTile ancestorResource = null;
try {
// TODO: Revise this to reflect that the parent layer is only requested while the algorithm
// continues
// to search for the layer matching the criteria.
// At this point the tile does not meet the render criteria but it may have its texture in
// memory.
// If so, register this tile as the resource tile. If not, then this tile will be the next
// level
// below a tile with texture in memory. So to provide progressive resolution increase, add
// this tile
// to the draw list. That will cause the tile to be drawn using its parent tile's texture, and
// it will
// cause it's texture to be requested. At some future call to this method the tile's texture
// will be in
// memory, it will not meet the render criteria, but will serve as the parent to a tile that
// goes
// through this same process as this method recurses. The result of all this is that a tile
// isn't rendered
// with its own texture unless all its parents have their textures loaded. In addition to
// causing
// progressive resolution increase, this ensures that the parents are available as the user
// zooms out, and
// therefore the layer remains visible until the user is zoomed out to the point the layer is
// no longer
// active.
if (tile.isTextureInMemory(dc.getTextureCache()) || tile.getLevelNumber() == 0) {
ancestorResource = this.currentResourceTile;
this.currentResourceTile = tile;
} else if (!tile.getLevel().isEmpty()) {
// this.addTile(dc, tile);
// return;
// Issue a request for the parent before descending to the children.
if (tile.getLevelNumber() < this.levels.getNumLevels()) {
// Request only tiles with data associated at this level
if (!this.levels.isResourceAbsent(tile)) this.requestTexture(dc, tile);
}
}
MercatorTextureTile[] subTiles =
tile.createSubTiles(this.levels.getLevel(tile.getLevelNumber() + 1));
for (MercatorTextureTile child : subTiles) {
if (this.isTileVisible(dc, child)) this.addTileOrDescendants(dc, child);
}
} finally {
if (ancestorResource != null) // Pop this tile as the currentResource ancestor
this.currentResourceTile = ancestorResource;
}
}