add explicit render platform channel method

android/src/main/kotlin/app/polyvox/filament/PolyvoxFilamentPlugin.kt

@@ -215,6 +215,12 @@ class PolyvoxFilamentPlugin: FlutterPlugin, MethodCallHandler, ActivityAware {
           result.success(null)
         }
       }
+      "render" -> {
+        executor.execute { 
+          _lib.render(_viewer!!, 0)
+          result.success(null)
+        }
+      }
       "setRendering" -> {
         _render = call.arguments as Boolean
         result.success(null)
@@ -480,7 +486,6 @@ class PolyvoxFilamentPlugin: FlutterPlugin, MethodCallHandler, ActivityAware {
           val args = call.arguments as ArrayList<Any?>
           val x = (args[0] as Double).toFloat()
           val y = (args[1] as Double).toFloat()
-          Log.v(TAG, "panUpdate ${x} ${y}")
           _lib.grab_update(_viewer!!, x, y)
           result.success("OK");
         }

lib/filament_controller.dart

@@ -15,6 +15,7 @@ abstract class FilamentController {
   Future createTextureViewer(int width, int height, { double devicePixelRatio = 1});
   Future setFrameRate(int framerate);
   Future setRendering(bool render);
+  Future render();
 
   Future resize(int width, int height, { double devicePixelRatio = 1, double contentScaleFactor=1});
   Future setBackgroundImage(String path);
@@ -111,6 +112,10 @@ class PolyvoxFilamentController extends FilamentController {
     await _channel.invokeMethod("setRendering",  render);
   }
 
+  Future render() async {
+    await _channel.invokeMethod("render");
+  }
+
   Future setFrameRate(int framerate) async {
     await _channel.invokeMethod("setFrameInterval",  1/ framerate);
   }
@@ -241,6 +246,7 @@ class PolyvoxFilamentController extends FilamentController {
   }
 
   Future removeAsset(FilamentAsset asset) async {
+    print("Removing asset : $asset");
     await _channel.invokeMethod("removeAsset", asset);
   }