[1] This method uses saving a model to the structure - the progressive mesh, which allows a smooth choice of detail levels depending on the current view.
Progressive meshes could be used also in other areas of computer technology such as a gradual transfer of data through the Internet or compression.
[2] A progressive mesh is a data structure which is created as the original model of the best quality simplifies a suitable decimation algorithm, which removes step by step some of the edges in the model (edge-collapse operation).
This forms a hierarchical structure which helps to create a model in the chosen level of detail.
This simplistic operation - ecol takes two connected vertices and replaces them with a single vertex.