I love Minecraft.  And if your kids are like my kids, they love Minecraft, too.  We’ve had a server running in our house for some time, but things got exciting for me when I discovered www.printcraft.org late last year.  You see, Santa (in his infinite wisdom) had just brought us a Makerbot Dual-head Replicator, but I was at a loss on how to easily get my kids (aged 7 and 10) creating their own 3D objects, not just skimming thingiverse.com for “cool” things to print.

Unfortunately, printcraft was a dedicated server, and I really wanted to let my kids go nuts on our own server;  after all, why not?  Between my wife and I, we have more CS degrees than any house should, so why couldn’t I get something rigged up?

I’m not going to give detailed step-by-step instructions here; I may do that someday, but the process is still a little jury rigged for public consumption.  But, here’s the gist of what I did.

First, I had to take the plunge and upgrade our server to support mods.  In particular, I’m currently running the craftbukkit-1.5.1-R0.1-20130330.075504-28.jar as my server, with the WorldEdit v5.5.5 plugin (I’m also running PermissionsBukkit-2.0 for permission control, Multiverse-Core-2.5 for multiple worlds in one server and Multiverse-SignPortals-2.5 to let me create signs that can be clicked to teleport).  The key feature of WorldEdit is that it lets you run javascript scripts from within Minecraft, and those scripts let you have full access to the server data-structures.

Fortunately, Paul Harter (the creator of printcraft) had posted his core script on github and while it wasn’t a load-and-go kind of script, it served as a great starting point for rolling my own server.  For anyone who cares, it looks like you’d expect:

While Paul’s original script is based on the idea of printing out everything within a predefined region, I opted to use the ability of WorldEdit to marker regions in the world.  So, my script assumes you’ve set a region to print, and then it traverses through that region, collecting up the blocks it finds.  It’s currently pretty limited in that it only supports square blocks (no ladders, chests, stairs, slabs, etc).   I divided the main blocks into two sets, and write out two scripts, one for each of the two kinds of blocks.

This is the second key thing Paul did:  he didn’t bother to create the STL file directly, but rather wrote out OpenSCAD programs.  OpenSCAD is a “programmers 3D modeler”, in that it lets you write programs that create models using constructive solid geometry.  So, printcraft creates a list of cubes and then merges them into a model;  OpenSCAD takes care of turning that union of those cubes into a proper model, which you can then save as STL.

So, the process is simple.  First, my kids create something they want printed in Minecraft.  Here’s a model my son made (the stone and dirt will be written out as separate models):

Next, I run the script I wrote, derived from Paul’s printcraft script, generating two OpenSCAD programs.  I then load each into OpenSCAD and generate STL files from them.  Here’s one:

Finally, I load both files into Makerware, size them as desired and select which is printed with which extruder:

And then, we wait for the Replicator to finish printing (a little longer than any of us would like)!

I won’t pretend this was a simple, smooth process, but it was fun!  And, most importantly, now I can print whatever my kids care to think up, without them having to learn a 3D modeling program.  I suspect that they will soon want to learn something more powerful, but for now I’m looking forward to seeing what they come up with.