private Spatial loadGltfGen() {
        GltfModelKey k = new GltfModelKey("jme3test/normalmapCompare/NormalTangentMirrorTest.gltf");
        Spatial sp = assetManager.loadModel(k);
        MikktspaceTangentGenerator.generate(loadedSpatial);
        modelTxt.setText("GLTF  - regen tg");
        return sp;
    }
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