GeometryCompressionUtils is an addon, and must be imported explicitly, see Installation#Addons.
import * as GeometryCompressionUtils from 'three/addons/utils/GeometryCompressionUtils.js';
Compressed the given geometry's normal attribute by the selected encode method.
geometry
The geometry whose normals should be compressed.
encodeMethod
The compression method.
Compressed the given geometry's position attribute.
geometry
The geometry whose position values should be compressed.
Compressed the given geometry's uv attribute.
geometry
The geometry whose texture coordinates should be compressed.