Hey there! I hope you all are having a wonderful time with Minecraft. I first encountered it shortly after it came out and I was impressed with its powerful simplicity. There's just so many things you can do with Minecraft -- I've just scratched the surface with TopoMC so far, and I'm looking forward to doing more.
When I was a kid my favorite maps were topographic maps. I collected all the maps for the area around where I grew up (I still have them!) and I loved just how detailed they were. The elevation lines, the little icons for buildings and churches and towers, the lines for the roads, all that stuff. When I got older and started playing with computers, the USGS was just starting to put some data out on the Internet. Back in 1990, I used to download files from their FTP sites on my 2400 baud modem; now in 2011, I can retrieve data from their web services on my cable modem over a thousand times faster!
The USGS publishes a great deal of data but TopoMC only uses two types: elevation and landcover. Elevation data is what it sounds like -- an elevation datum in meters above sea level every so often across the entire country. The spacing between the elevation datums is the resolution of the data. The entire country except Alaska is available at a resolution of one arc-second (about thirty meters) but many places are available at one-third arc-second and some like Seattle are available at one-ninth arc-second! This elevation data is used by
TopoMC to determine the relative height of any particular piece of terrain on the map, which is pretty awesome. I think the landcover data is even more awesome -- that's how TopoMC knows whether to place water or dirt or grass or stone or trees! Landcover data describes the land at any particular part of the map: water, forest, beach, forest, things like that. This data is only available at one resolution: every thirty meters across the entire country.
As most users want Minecraft worlds that are scaled larger than thirty real-world meters to one Minecraft block, TopoMC transforms the elevation and landcover data to suit the needs of the user. What this means is that for every real data point for landcover and elevation, there are a bunch of data points that need to be generated. The default scaling values are 6:1 which means TopoMC needs to generate 24 additional data points for each real data point. Your map has a 2:1 ratio which means TopoMC needs to generate
224 additional data points for each original data point! How does the software do this? This bit is complicated -- if there's something you don't understand, just ask in the comments and I'll try to explain! The horizontal interpolation of elevation data is straightforward: for each point, I find the nearest points and generate a weighted mean based on the distance between those points and the new point. The Wikipedia page on weighted means has an example. Using their numbers, if I found the two nearest points to have elevations of 80 and 90 meters and distances from the new point of 20 and 30 meters, respectively, the new point's estimated elevation would be 86. The vertical scaling is even simpler: if the real elevation is 86 degrees, I divide that by the scaling factor. If the real elevation is 86 and the vertical scaling factor is 6, then the resulting elevation would be 14 blocks above sea level. As an aside, sea level is traditionally at the halfway point in Minecraft worlds, but the worlds generated by TopoMC tend to make sea level much lower to have more space for natural elevations. Changes in Minecraft will soon permit much taller worlds, which will make this problem mostly go away. Anyway, back to interpolation. Landcover data is only interpolated horizontally, as vertical scaling has no impact on what type of terrain is in use. Weighted means are no help when dealing with landcover data, so I use a weighted majority algorithm to determine what sort of terrain should be placed on scaled terrain. If a new point is surrounded by water, it'll be water. If a new point is surrounded by equal amounts of water and sand, it'll be a coin flip -- unless the water is close and the sand is far away, in which case it'll be water. Make sense? If not, let me know in the comments and I'll answer as best I can.
There's one last thing I'd like to share with you all about TopoMC. I have released the software with an open source license, which means anyone else in the world can download it and use it and modify it as long as they give me credit for what I've done. Why is this so important? All sorts of reasons! Want to understand more about how TopoMC works? Download the source code and figure it out or ask me questions and I'll explain. Want to fix a bug like those pesky mid-ocean waterfalls where the water swells up for no reason, or maybe add a feature like supporting a new kind of tree or flower? Download the source code and make the changes yourself! This is something that is impossible with most software these days, like Microsoft Windows or Minecraft itself. The best you can do is tell the people who make it what doesn't work or how you would like them to change it, or maybe if you're lucky get an aftermarket addon that does what you need. With software like TopoMC or Linux or any other open source software, you are only limited by your time, patience and ability. This is how I learned to write software, and I do it for a living, so I think I'm doing something right! :-) If any of you like this sort of thing, let me know and I'll help you out as best I can.
Thank you for listening, and I hope you continue to enjoy Minecraft!
