Encoding and decoding of property data, such as colour values, associated with vertices forming 3D objects. From an analysis of connectivity data, a spiral-like scanning path of the vertices within the 3D model is obtained. The colour values are mapped to a 2D image, each attribute value to a pixel. Next, the mapped 2D image is encoded. To increase redundancies in the 2D image, the spiral-like path is split into path segments, each forming a turn in the spiral; each path segment is assigned to a respective line of the 2D image; and the colour values of each path segment are mapped, in the same order, to the respective line of the 2D image. Successive lines in the 2D image thus contain the colour values of neighbouring vertices in the 3D object, and a better encoding can be achieved.