Try to add some lights to your scene. E.g.
const ambientLight = new THREE.AmbientLight( 0xcccccc, 0.4 );
scene.add( ambientLight );
const pointLight = new THREE.PointLight( 0xffffff, 0.8 );
scene.add( pointLight );
Try to add some lights to your scene. E.g.
const ambientLight = new THREE.AmbientLight( 0xcccccc, 0.4 );
scene.add( ambientLight );
const pointLight = new THREE.PointLight( 0xffffff, 0.8 );
scene.add( pointLight );