Make perspective transformation look exactly same on iOS and Android (#…

…18302)

Summary:
There is a variation in iOS and Android output while performing perspective transformation. The variation exists even when used in Android devices with different screen density.
Pull Request resolved: #18302

Differential Revision: D13877483

Pulled By: cpojer

fbshipit-source-id: e48be047a8047c7562722923a67666cb098243d8

ReactAndroid/src/main/java/com/facebook/react/uimanager/BaseViewManager.java

@@ -44,7 +44,7 @@ public abstract class BaseViewManager<T extends View, C extends LayoutShadowNode
   private static final String PROP_TRANSLATE_Y = "translateY";
 
   private static final int PERSPECTIVE_ARRAY_INVERTED_CAMERA_DISTANCE_INDEX = 2;
-  private static final float CAMERA_DISTANCE_NORMALIZATION_MULTIPLIER = 5;
+  private static final float CAMERA_DISTANCE_NORMALIZATION_MULTIPLIER = (float)Math.sqrt(5);
 
   /**
    * Used to locate views in end-to-end (UI) tests.
@@ -234,8 +234,12 @@ private static void setTransformProperty(View view, ReadableArray transforms) {
       float scale = DisplayMetricsHolder.getScreenDisplayMetrics().density;
 
       // The following converts the matrix's perspective to a camera distance
-      // such that the camera perspective looks the same on Android and iOS
-      float normalizedCameraDistance = scale * cameraDistance * CAMERA_DISTANCE_NORMALIZATION_MULTIPLIER;
+      // such that the camera perspective looks the same on Android and iOS.
+      // The native Android implementation removed the screen density from the
+      // calculation, so squaring and a normalization value of
+      // sqrt(5) produces an exact replica with iOS.
+      // For more information, see https://github.com/facebook/react-native/pull/18302
+      float normalizedCameraDistance = scale * scale * cameraDistance * CAMERA_DISTANCE_NORMALIZATION_MULTIPLIER;
       view.setCameraDistance(normalizedCameraDistance);
 
     }