applyTextureTransform( mapDef, texture ) {

		let didTransform = false;
		const transformDef = {};

		if ( texture.offset.x !== 0 || texture.offset.y !== 0 ) {

			transformDef.offset = texture.offset.toArray();
			didTransform = true;

		}

		if ( texture.rotation !== 0 ) {

			transformDef.rotation = texture.rotation;
			didTransform = true;

		}

		if ( texture.repeat.x !== 1 || texture.repeat.y !== 1 ) {

			transformDef.scale = texture.repeat.toArray();
			didTransform = true;

		}

		if ( didTransform ) {

			mapDef.extensions = mapDef.extensions || {};
			mapDef.extensions[ 'KHR_texture_transform' ] = transformDef;
			this.extensionsUsed[ 'KHR_texture_transform' ] = true;

		}

	}
Applies a texture transform, if present, to the map definition. Requires
the KHR_texture_transform extension.

@param {Object} mapDef
@param {THREE.Texture} texture