Change Placemark default depth offset from -0.1 to -0.015 to prevent texture from protruding through the terrain.

Fix placemarks altitude mode in PlacemarksMilStd2525Activity to be correctly rendered on the top of the surface.
Use billboarding approach of placemarks rendering to prevent clipping by terrain as described in MIL-STD-2525C APPENDIX F.5.1.1.2.

Author: EMaksymenko

worldwind-examples/src/main/java/gov/nasa/worldwindx/PlacemarksMilStd2525Activity.java

@@ -86,6 +86,7 @@ protected void onPostExecute(Void notUsed) {
             Placemark drone = new Placemark(
                 Position.fromDegrees(32.4520, 63.44553, 3000),
                 MilStd2525.getPlacemarkAttributes("SFAPMFQM--GIUSA", modifiers, null));
+            drone.getAttributes().setDrawLeader(true);
 
             symbolLayer.addRenderable(drone);
 
@@ -96,6 +97,7 @@ protected void onPostExecute(Void notUsed) {
             Placemark launcher = new Placemark(
                 Position.fromDegrees(32.4014, 63.3894, 0),
                 MilStd2525.getPlacemarkAttributes("SHGXUCFRMS----G", modifiers, null));
+            launcher.setAltitudeMode(WorldWind.CLAMP_TO_GROUND);
 
             symbolLayer.addRenderable(launcher);
 
@@ -109,6 +111,7 @@ protected void onPostExecute(Void notUsed) {
             Placemark machineGun = new Placemark(
                 Position.fromDegrees(32.3902, 63.4161, 0),
                 MilStd2525.getPlacemarkAttributes("SFGPEWRH--MTUSG", modifiers, null));
+            machineGun.setAltitudeMode(WorldWind.CLAMP_TO_GROUND);
 
             symbolLayer.addRenderable(machineGun);
 

worldwind-examples/src/main/java/gov/nasa/worldwindx/milstd2525/MilStd2525.java

@@ -269,7 +269,8 @@ public Bitmap createBitmap() {
             Rect bounds = imageInfo.getImageBounds();       // The extents of the image, including text modifiers
             this.placemarkOffset = new Offset(
                 WorldWind.OFFSET_PIXELS, centerPoint.x, // x offset
-                WorldWind.OFFSET_PIXELS, bounds.height() - centerPoint.y); // y offset converted to lower-left origin
+                // Use billboarding or lollipopping to prevent icon clipping by terrain as described in MIL-STD-2525C APPENDIX F.5.1.1.2
+                WorldWind.OFFSET_PIXELS, 0/*bounds.height() - centerPoint.y*/); // y offset converted to lower-left origin
 
             // Apply the placemark offset to the attributes on the main thread. This is necessary to synchronize write
             // access to placemarkAttributes from the thread that invokes this BitmapFactory and read access from the

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

@@ -60,7 +60,7 @@ public interface LevelOfDetailSelector {
      */
     protected static final double DEFAULT_EYE_DISTANCE_SCALING_THRESHOLD = 1e6;
 
-    protected static final double DEFAULT_DEPTH_OFFSET = -0.1;
+    protected static final double DEFAULT_DEPTH_OFFSET = -0.03;
 
     private static Vec3 placePoint = new Vec3();
 
@@ -684,8 +684,9 @@ protected void doRender(RenderContext rc) {
 
         // Compute a screen depth offset appropriate for the current viewing parameters.
         double depthOffset = 0;
-        if (this.cameraDistance < rc.horizonDistance) {
-            depthOffset = DEFAULT_DEPTH_OFFSET;
+        double absTilt = Math.abs( rc.camera.tilt );
+        if (this.cameraDistance < rc.horizonDistance && absTilt <= 90) {
+            depthOffset = ( 1 - absTilt / 90 ) * DEFAULT_DEPTH_OFFSET;
         }
 
         // Project the placemark's model point to screen coordinates, using the screen depth offset to push the screen