scene.overrideMaterial

threejs有一个属性overrideMaterial在渲染物体时会优先使用这个属性覆盖其他材质

function renderObjects( renderList, scene, camera ) {

	const overrideMaterial = scene.isScene === true ? scene.overrideMaterial : null;

	for ( let i = 0, l = renderList.length; i < l; i ++ ) {

		const renderItem = renderList[ i ];

		const object = renderItem.object;
		const geometry = renderItem.geometry;
		const material = overrideMaterial === null ? renderItem.material : overrideMaterial;
		const group = renderItem.group;

		if ( object.layers.test( camera.layers ) ) {

			renderObject( object, scene, camera, geometry, material, group );

		}

	}

}