diff --git a/src/java/com/threerings/media/AbstractMedia.java b/src/java/com/threerings/media/AbstractMedia.java
index da4b7902..c4ebb563 100644
--- a/src/java/com/threerings/media/AbstractMedia.java
+++ b/src/java/com/threerings/media/AbstractMedia.java
@@ -271,10 +271,43 @@ public abstract class AbstractMedia
         _firstTick = tickStamp;
     }
 
+    /**
+     * If this media's size or location are changing, it should create a new
+     * rectangle from its old boudns (new Rectangle(_bounds)), then effect the
+     * bounds changes and then call this method with the old bounds and this
+     * method will either merge the new bounds with the old to create a single
+     * dirty rectangle or dirty them separately depending on which is more
+     * appropriate. It will also behave properly if this media is not currently
+     * managed (not being rendered) by NOOPing.
+     *
+     * <em>Do not</em> pass {@link #_bounds} to this method. The rectangle
+     * passed in will be modified and then passed on to the region manager
+     * which will modify it further.
+     */
+    protected void invalidateAfterChange (Rectangle obounds)
+    {
+        // if we're not added we need not dirty
+        if (_mgr == null) {
+            return;
+        }
+
+        // if our new bounds intersect our old bounds, grow a single dirty
+        // rectangle to incorporate them both
+        if (_bounds.intersects(obounds)) {
+            obounds.add(_bounds);
+        } else {
+            // otherwise invalidate our new bounds separately
+            _mgr.getRegionManager().invalidateRegion(_bounds);
+        }
+
+        // finally invalidate the original/merged bounds
+        _mgr.getRegionManager().addDirtyRegion(obounds);
+    }
+
     /**
      * Called by the media manager after the media is removed from service.
-     * Derived classes may override this method, but should be sure to
-     * call <code>super.shutdown()</code>.
+     * Derived classes may override this method, but should be sure to call
+     * <code>super.shutdown()</code>.
      */
     protected void shutdown ()
     {
diff --git a/src/java/com/threerings/media/animation/Animation.java b/src/java/com/threerings/media/animation/Animation.java
index d0be45d5..f193423d 100644
--- a/src/java/com/threerings/media/animation/Animation.java
+++ b/src/java/com/threerings/media/animation/Animation.java
@@ -69,25 +69,14 @@ public abstract class Animation extends AbstractMedia
             return; // no-op
         }
 
-        // start with our current bounds
-        Rectangle dirty = new Rectangle(_bounds);
+        // make a note of our current bounds
+        Rectangle obounds = new Rectangle(_bounds);
 
         // move ourselves
         super.setLocation(x, y);
 
-        // grow the dirty rectangle to incorporate our new bounds and pass
-        // the dirty region to our region manager
-        if (_mgr != null) {
-            // if our new bounds intersect our old bounds, grow a single
-            // dirty rectangle to incorporate them both
-            if (_bounds.intersects(dirty)) {
-                dirty.add(_bounds);
-            } else {
-                // otherwise invalidate our new bounds separately
-                _mgr.getRegionManager().invalidateRegion(_bounds);
-            }
-            _mgr.getRegionManager().addDirtyRegion(dirty);
-        }
+        // this method will invalidate our old and new bounds efficiently
+        invalidateAfterChange(obounds);
     }
 
     // documentation inherited
diff --git a/src/java/com/threerings/media/sprite/Sprite.java b/src/java/com/threerings/media/sprite/Sprite.java
index 9abf1c6a..c026b7a2 100644
--- a/src/java/com/threerings/media/sprite/Sprite.java
+++ b/src/java/com/threerings/media/sprite/Sprite.java
@@ -154,8 +154,8 @@ public abstract class Sprite extends AbstractMedia
             return; // no-op
         }
 
-        // start with our current bounds
-        Rectangle dirty = new Rectangle(_bounds);
+        // make a note of our current bounds
+        Rectangle obounds = new Rectangle(_bounds);
 
         // move ourselves
         _ox = x;
@@ -165,19 +165,8 @@ public abstract class Sprite extends AbstractMedia
         // of our current bounds
         updateRenderOrigin();
 
-        // grow the dirty rectangle to incorporate our new bounds and pass
-        // the dirty region to our region manager
-        if (_mgr != null) {
-            // if our new bounds intersect our old bounds, grow a single
-            // dirty rectangle to incorporate them both
-            if (_bounds.intersects(dirty)) {
-                dirty.add(_bounds);
-            } else {
-                // otherwise invalidate our new bounds separately
-                _mgr.getRegionManager().invalidateRegion(_bounds);
-            }
-            _mgr.getRegionManager().addDirtyRegion(dirty);
-        }
+        // this method will invalidate our old and new bounds efficiently
+        invalidateAfterChange(obounds);
     }
 
     // documentation inherited