Add 3D capability to Ellipse shapes (#209)

* Add element buffer cache

* Fix element buffer cache

* Store element buffer in render resource cache

* Refactor buffer retrieval from cache

* Refactor buffer retrieval and reassembly

* Rename assembly function

* Rename variables

* Simplify buffer retrieval logic

* Switch to Range object for managing buffer indices

* Add initial 3d capabilities

* Add extrusion property and getter/setters

* Add extrude vertex generation

* Fix spelling of function assembleElementsToCache function

* Add extruded sides

* Add vertical lines

* Fix rendering state issues with extrusion

* Clean up naming

* Update Ellipse tutorial for 3D ellipses

* Remove extra lines

* Fix bounding sector calculation for 3D ellipse

* Change scratch variable names to match convention

* Change scratch variable names to match convention

* Change scratch variable names to match convention, see notes
- Previous commit message did not include notes on the refactor to use a generic element buffer
- The extruded elements are always computed and incorporated into an element buffer
- The vertex array now uses a plain float array in order to provide indexed assignment

* Cleanup of comments and spelling

* Additional comments and cleanup

* Refactor spine computation into a function

* Add optional Range objects to BufferObject

* Change interval count determination method name

* Change interval property name

* Remove unnecessary local variable assignment

* Update property name formatting

* Move spine radius initialization

* Utilize simplified globe radius value

* Refactor index offset to function and refine addVertex

* Utilize static client vertex array

* Update documentation

* Initial addition of texture capability

* Revert single vertex array and clean up formatting

* Fix documentation

Author: zglueck

worldwind-tutorials/src/main/assets/ellipse_tutorial.html

@@ -24,12 +24,14 @@ <h1>Ellipse Tutorial</h1>
     Demonstrates how to add an Ellipse to a RenderableLayer.
 </p>
 <p>
-    This example renders four different ellipses on the globe.
+    This example renders six different ellipses on the globe.
 <ul>
     <li>The Northwestern ellipse demonstrates the default styling and configuration.</li>
     <li>The Northeastern ellipse uses custom attributes.</li>
-    <li>The Southwestern ellipse has a 45 degree heading.</li>
-    <li>The Southeastern ellipse displays a circle.</li>
+    <li>The Western ellipse has a 45 degree heading.</li>
+    <li>The Eastern ellipse displays a circle.</li>
+    <li>The Southwestern ellipse is at an altitude of 200km.</li>
+    <li>The Southeastern ellipse is at an altitude of 200km, extrude, and custom attributes.</li>
 </ul>
 </p>
 <h2>Example</h2>
@@ -90,6 +92,20 @@ <h3>EllipseFragment.java</h3>
         ellipse.setFollowTerrain(true); // cause the ellipse geometry to follow the terrain surface
         tutorialLayer.addRenderable(ellipse);
 
+        // Create an ellipse with the default attributes, an altitude of 200 km, and a 500km major-radius and a 300km
+        // minor-radius.
+        ellipse = new Ellipse(new Position(25, -120, 200e3), 500000, 300000);
+        tutorialLayer.addRenderable(ellipse);
+
+        // Create an ellipse with custom attributes that make the interior 50% transparent and an extruded outline with
+        // vertical lines
+        attrs = new ShapeAttributes();
+        attrs.setInteriorColor(new Color(1, 1, 1, 0.5f)); // 50% transparent white
+        attrs.setDrawVerticals(true);
+        ellipse = new Ellipse(new Position(25, -100, 200e3), 500000, 300000, attrs);
+        ellipse.setExtrude(true);
+        tutorialLayer.addRenderable(ellipse);
+
         return wwd;
     }
 }

worldwind-tutorials/src/main/java/gov/nasa/worldwindx/EllipseFragment.java

@@ -61,6 +61,20 @@ public WorldWindow createWorldWindow() {
         ellipse.setFollowTerrain(true); // cause the ellipse geometry to follow the terrain surface
         tutorialLayer.addRenderable(ellipse);
 
+        // Create an ellipse with the default attributes, an altitude of 200 km, and a 500km major-radius and a 300km
+        // minor-radius.
+        ellipse = new Ellipse(new Position(25, -120, 200e3), 500000, 300000);
+        tutorialLayer.addRenderable(ellipse);
+
+        // Create an ellipse with custom attributes that make the interior 50% transparent and an extruded outline with
+        // vertical lines
+        attrs = new ShapeAttributes();
+        attrs.setInteriorColor(new Color(1, 1, 1, 0.5f)); // 50% transparent white
+        attrs.setDrawVerticals(true);
+        ellipse = new Ellipse(new Position(25, -100, 200e3), 500000, 300000, attrs);
+        ellipse.setExtrude(true);
+        tutorialLayer.addRenderable(ellipse);
+
         return wwd;
     }
 }

worldwind/src/main/java/gov/nasa/worldwind/render/BufferObject.java

@@ -6,10 +6,12 @@
 package gov.nasa.worldwind.render;
 
 import android.opengl.GLES20;
+import android.util.SparseArray;
 
 import java.nio.Buffer;
 
 import gov.nasa.worldwind.draw.DrawContext;
+import gov.nasa.worldwind.geom.Range;
 import gov.nasa.worldwind.util.Logger;
 
 public class BufferObject implements RenderResource {
@@ -24,6 +26,8 @@ public class BufferObject implements RenderResource {
 
     protected Buffer buffer;
 
+    public SparseArray<Range> ranges = new SparseArray<>();
+
     public BufferObject(int target, int size, Buffer buffer) {
         this.bufferTarget = target;
         this.bufferLength = (buffer != null) ? buffer.remaining() : 0;