update README

README.md

@@ -1,3 +1,22 @@
 # polyvox_filament
 
-3D rendering utilities for the Polyvox app.
+Flutter plugin wrapping the Filament renderer https://github.com/google/filament.
+
+Current Filament version: 1.25.0
+
+All:
+- clone Filament repository 
+- copy filament/include to ios/include
+- copy filament/libs/utils/include to ios/include
+
+(even though headers are under the iOS directory these are used across all platforms).
+
+Android:
+- build from Filament repository on Linux (build native, then build Android). Reminder that NDK >= 24 required.
+- copy out/android-release/filament/lib to android/src/main/jniLibs
+
+iOS:
+- filament-v1.25.0-ios.tgz
+
+Extract and move both lib/ and include/ to ./ios
+