Learning programming languages and developing software is important part of curricula at many educational institutions. Directly connected to that is a peer-to-peer sharing of program's source codes which is not always allowed. The article discusses the problem of plagiarism, especially the source code plagiarism and presents an excerpt of the results of the survey among students at

Viewshed is a basic visibility structure and represents all visible points from a given viewpoint. The paper gives a survey of non-parallel viewshed algorithms using regular spaced points. At first, a comprehensive background of the problem is given, then the existing methods (R3, R2, XDraw, method based on the line rasterisation) are introduced briefly. They have been implemented in 11 variants. Real terrain data and fractal generated terrains have been used for their comparison against spent CPU time and the accuracy of a computed visibility information.

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An algorithm for quasi-regular hexagon tessellation of uniformly distributed points is presented. At first, the needed definitions and notations are introduced. Then, the algorithm for the tessellation, based on "laying-down the sticks" analogy, is given. At the end, the estimation of the algorithm time complexity is done.