I get transfer gltf file , show in Cesium is black, Why?

[yangxin2017]

entity = viewer.entities.add({ name : 'sig2.gltf', position : position, orientation : orientation, model : { uri : url, minimumPixelSize : 128, maximumScale : 20000, color: Cesium.Color.RED, colorBlendMode: 0 } });
This is my obj file.
obj.zip

[lilleyse]

It looks like the problem is the obj doesn't have normals. obj2gltf doesn't generate normals anymore and neither does cesium, so the model appears black. If you are able to export the obj with normals that would fix the problem for now.

We have an issue open in Cesium for this: CesiumGS/cesium#5838. I'll close this in the meantime.