A method for the level of detail processing in the visualization of virtual models. In the method, the patches for each object are sorted according to the visualization error for producing the fine detail level of the model. When more than one geometry level is used, reduced detail levels are formed so that the patches are in the same order as in the fine detail level. When visualizing the model, a sliding window is placed on the model according to a determined quality factor. The sliding window is positioned on the levels so that it can be partially on two different levels.