Merge pull request #3387 from sebavan/master

PBR Fix

src/Materials/PBR/babylon.pbrBaseMaterial.ts

@@ -828,8 +828,8 @@
                         defines.REFRACTION = true;
                         defines.REFRACTIONMAP_3D = refractionTexture.isCube;
                         defines.GAMMAREFRACTION = refractionTexture.gammaSpace;
-                        defines.REFRACTIONMAP_OPPOSITEZ = reflectionTexture.invertZ;
-                        defines.LODINREFRACTIONALPHA = reflectionTexture.lodLevelInAlpha;
+                        defines.REFRACTIONMAP_OPPOSITEZ = refractionTexture.invertZ;
+                        defines.LODINREFRACTIONALPHA = refractionTexture.lodLevelInAlpha;
 
                         if (this._linkRefractionWithTransparency) {
                             defines.LINKREFRACTIONTOTRANSPARENCY = true;