getCache( property, type ) {

		let node = _propertyCache.get( property );

		if ( node === undefined ) {

			node = materialReference( property, type );

			_propertyCache.set( property, node );

		}

		return node;

	}
Returns a cached reference node for the given property and type.

@param {string} property - The name of the material property.
@param {string} type - The uniform type of the property.
@return {MaterialReferenceNode} A material reference node representing the property access.