Probably final this time 😉 I was trying to find a compromise between speed and quality and came up with an idea of triangle-based cubic interpolation. Fortunately it turned out that such beast already existed – http://cran.r-project.org/web/packages/akima/. It’s several times faster than Natural Neighbour and gives better results than Linear Interpolation, although there are some artefacts in sharp transition areas (they can be avoided or overcome with smart point placing). Just another interesting option for preview during development. For production quality, you should definitely go with Natural Neighbour Interpolation.
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