add NORMAL_TYPE define to PBRTerrain.j3md

jme3-terrain/src/main/resources/Common/MatDefs/Terrain/PBRTerrain.j3md

@@ -26,6 +26,9 @@ MaterialDef PBR Terrain {
         Texture2D SplatRoughnessMetallicMap -LINEAR
         Texture2D SplatEmissiveMap -LINEAR
 
+        //The type of normal map: -1.0 (DirectX), 1.0 (OpenGl)
+        Float NormalType : -1.0
+
         // Specular-AA
         Boolean UseSpecularAA : true
         // screen space variance,Use the slider to set the strength of the geometric specular anti-aliasing effect between 0 and 1. Higher values produce a blurrier result with less aliasing.
@@ -276,6 +279,8 @@ MaterialDef PBR Terrain {
             STATIC_SUN_EXPOSURE : StaticSunExposure
             BRIGHTEN_INDOOR_SHADOWS : BrightenIndoorShadows
 
+            NORMAL_TYPE: NormalType
+
             USE_FIRST_LAYER_AS_TRANSPARENCY : UseFirstLayerAsTransparency
 
             DISCARD_ALPHA : AlphaDiscardThreshold