Add instance culling function in InstancedGeometry

jme3-core/src/main/java/com/jme3/scene/instancing/InstancedGeometry.java

@@ -58,11 +58,14 @@
 import java.nio.FloatBuffer;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.function.BiFunction;
 
 public class InstancedGeometry extends Geometry {
 
     private static final int INSTANCE_SIZE = 16;
 
+    private static BiFunction<Camera, Geometry, Boolean> instanceCullingFunction = new DefaultInstanceCullingFunction();
+
     private VertexBuffer[] globalInstanceData;
     private VertexBuffer transformInstanceData;
     private Geometry[] geometries = new Geometry[1];
@@ -95,6 +98,22 @@ public InstancedGeometry(String name) {
         setMaxNumInstances(1);
     }
 
+    /**
+     * Set the function used for culling instances from being rendered.
+     * Default is {@link DefaultInstanceCullingFunction}.
+     */
+    public static void setInstanceCullingFunction(BiFunction<Camera, Geometry, Boolean> instanceCullingFunction) {
+        InstancedGeometry.instanceCullingFunction = instanceCullingFunction;
+    }
+
+    /**
+     * @return The instance culling function or null if there isn't any.
+     * Default is {@link DefaultInstanceCullingFunction}.
+     */
+    public static BiFunction<Camera, Geometry, Boolean> getInstanceCullingFunction() {
+        return instanceCullingFunction;
+    }
+
     /**
      * Global user specified per-instance data.
      *
@@ -284,14 +303,9 @@ public void updateInstances() {
                     }
                 }
 
-                if (cam != null) {
-                    BoundingVolume bv = geom.getWorldBound();
-                    int save = cam.getPlaneState();
-                    cam.setPlaneState(0);
-                    FrustumIntersect intersect = cam.contains(bv);
-                    cam.setPlaneState(save);
-
-                    if (intersect == FrustumIntersect.Outside) {
+                if (cam != null && instanceCullingFunction != null) {
+                    boolean culled = instanceCullingFunction.apply(cam, geom);
+                    if (culled) {
                         numCulledGeometries++;
                         continue;
                     }
@@ -458,4 +472,22 @@ protected void cleanup() {
         allInstanceData = null;
         geometries = null;
     }
+
+    /**
+     * By default, it checks if geometry is in camera frustum and culls it
+     * if it is outside camera view.
+     */
+    public static class DefaultInstanceCullingFunction implements BiFunction<Camera, Geometry, Boolean> {
+
+        @Override
+        public Boolean apply(Camera cam, Geometry geom) {
+            BoundingVolume bv = geom.getWorldBound();
+            int save = cam.getPlaneState();
+            cam.setPlaneState(0);
+            FrustumIntersect intersect = cam.contains(bv);
+            cam.setPlaneState(save);
+
+            return intersect == FrustumIntersect.Outside;
+        }
+    }
 }