function createDefaultMaterial( cache ) {

	if ( cache[ 'DefaultMaterial' ] === undefined ) {

		cache[ 'DefaultMaterial' ] = new MeshStandardMaterial( {
			color: 0xFFFFFF,
			emissive: 0x000000,
			metalness: 1,
			roughness: 1,
			transparent: false,
			depthTest: true,
			side: FrontSide
		} );

	}

	return cache[ 'DefaultMaterial' ];

}
Specification: https://github.com/KhronosGroup/glTF/blob/master/specification/2.0/README.md#default-material

@private
@param {Object<string, Material>} cache
@return {Material}