Artifact appears on polygon when viewed from a low angle

CesiumJS
1

image
image2852×806 278 KB

image
image2870×808 268 KB

angle of view is lower, the shadow will appear，i want the shadow disappear

this is code:

var viewer = new Cesium.Viewer("cesiumContainer");
viewer.scene.globe.enableLighting = false;
viewer.shadows = false;
var redPolygon = viewer.entities.add({
  name: "Red polygon on surface",
  polygon: {
    hierarchy: Cesium.Cartesian3.fromDegreesArrayHeights([
      116.31282326252641,
                            40.02362677720817,
                            -2.502101525,
      116.31980360345781,
                            40.02362677720817,
                            -2.502101525,
      116.31980360345781,
                            40.012985336043336,
                            -2.502101525,
      116.31282326252641,
                            40.012985336043336,
                            -2.502101525,
       116.31282326252641,
                            40.02362677720817,
                            -2.502101525
    ]),
    height: 1000,
    material: Cesium.Color.RED,
  },
});

viewer.zoomTo(viewer.entities);