Total or Selective Decompression of a Compressed Plane Triangulation

Efficient techniques to compress/decompress triangulations are commonly used when dealing with huge size meshes. Optimal compression methods which allow to decompress just a part of a triangulation are nevertheless rather unpopular in practice. In this paper we present a simple technique which allows encoding plane triangulations without knowing a priori whether the whole mesh or just a part of it will have to be decompressed. In a pre-processing step the triangulation is encoded following a lossless approach. The compressed representation of the triangulation consists on a string of three types of symbols, and requires at most 5 bits per vertex. Provided the whole mesh has to be decoded, the method finishes here. If, on the contrary, just a query zone has to be extracted, the encoding sequence will be slightly modified, and a new sequence will be obtained from which just a query zone of the triangulation can be decompressed in optimal time. The method is suitable for those applications requiring to manage small parts of huge plane triangulations or to send via web the whole triangular mesh.