Use exact device screen density on tile details calculation.

worldwind/src/main/java/gov/nasa/worldwind/globe/BasicTessellator.java

@@ -35,7 +35,7 @@ public class BasicTessellator implements Tessellator, TileFactory {
     // ~0.6 meter resolution
     protected LevelSet levelSet = new LevelSet(new Sector().setFullSphere(), new Location(-90, -180), new Location(90, 90), 20, 32, 32);
 
-    protected double detailControl = 80;
+    protected double detailControl = 32;
 
     protected final List<Tile> topLevelTiles = new ArrayList<>();
 

worldwind/src/main/java/gov/nasa/worldwind/shape/TiledSurfaceImage.java

@@ -34,16 +34,16 @@ public class TiledSurfaceImage extends AbstractRenderable {
 
     protected ImageOptions imageOptions;
 
-    protected double detailControl = 4;
+    protected double detailControl = 1;
 
     protected final List<Tile> topLevelTiles = new ArrayList<>();
 
     /**
      * Memory cache for this layer's subdivision tiles. Each entry contains an array of four image tiles corresponding
-     * to the subdivision of the group's common parent tile. The cache is configured to hold 500 groups, a number
+     * to the subdivision of the group's common parent tile. The cache is configured to hold 1000 groups, a number
      * empirically determined to be sufficient for storing the tiles needed to navigate a small region.
      */
-    protected final LruMemoryCache<String, Tile[]> tileCache = new LruMemoryCache<>(500);
+    protected final LruMemoryCache<String, Tile[]> tileCache = new LruMemoryCache<>(1000);
 
     protected SurfaceTextureProgram activeProgram;
 
@@ -158,6 +158,10 @@ protected void addTileOrDescendants(RenderContext rc, ImageTile tile) {
         ImageSource tileImageSource = tile.getImageSource();
         if (tileImageSource != null) { // tile has an image source; its level is not empty
             Texture tileTexture = rc.getTexture(tileImageSource);
+            // retrieve top level tiles to avoid black holes when navigating and zooming out camera
+            if (tileTexture == null) {
+                tileTexture = rc.retrieveTexture(tileImageSource, this.imageOptions); // puts retrieved textures in the cache
+            }
             if (tileTexture != null) { // tile has a texture; use it as a fallback tile for descendants
                 this.ancestorTile = tile;
                 this.ancestorTexture = tileTexture;

worldwind/src/main/java/gov/nasa/worldwind/util/Tile.java

@@ -5,8 +5,6 @@
 
 package gov.nasa.worldwind.util;
 
-import android.util.DisplayMetrics;
-
 import java.util.Arrays;
 import java.util.Collection;
 
@@ -291,14 +289,7 @@ public boolean mustSubdivide(RenderContext rc, double detailFactor) {
         this.distanceToCamera = this.distanceToCamera(rc);
         double texelSize = this.texelSizeFactor * rc.globe.getEquatorialRadius();
         double pixelSize = rc.pixelSizeAtDistance(this.distanceToCamera);
-        double densityFactor = 1.0;
-
-        // Adjust the subdivision factory when the display density is low. Values of detailFactor have been calibrated
-        // against high density devices. Low density devices need roughly half the detailFactor.
-        if (rc.resources.getDisplayMetrics().densityDpi <= DisplayMetrics.DENSITY_MEDIUM) {
-            densityFactor = 0.5;
-        }
-
+        double densityFactor = rc.resources.getDisplayMetrics().density;
         return texelSize > (pixelSize * detailFactor * densityFactor);
     }