private Material createSPLightingMat() {
        renderManager.setPreferredLightMode(LightMode.SinglePass);
        Material mat = new Material(assetManager, "Common/MatDefs/Light/Lighting.j3md");
        mat.setTexture("DiffuseMap", assetManager.loadTexture(new TextureKey(
                "jme3test/normalmapCompare/NormalTangentMirrorTest_BaseColor.png", flipTextures)));
        mat.setTexture("NormalMap", assetManager.loadTexture(
                new TextureKey("jme3test/normalmapCompare/NormalTangentTest_Normal.png", flipTextures)));
        mat.setFloat("NormalType", 1);
        materialTxt.setText("SP Lighting");
        return mat;
    }
This test cycles through a model exported in different formats and with different materials with tangents
generated in different ways. The normal map should look correct in all cases. Refer to
https://github.com/KhronosGroup/glTF-Sample-Models/tree/master/2.0/NormalTangentMirrorTest for details on
the correct result and debugging.
jme3-examples/src/main/java/jme3test/material/TestNormalMappingConsistency.java