protected void setNeedToRecalculateNormals() {
        affectedAreaBBox = new BoundingBox(getWorldTranslation(), Float.MAX_VALUE, Float.MAX_VALUE, Float.MAX_VALUE);
    }
This will cause all normals for this terrain quad to be recalculated
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/TerrainQuad.java