![A plywood slab carved with CNC into a topographic representation of California][main_image]
# A birthday wish
Last summer, I wanted to get my wife something nice for her birthday. For many years, she had
expressed an occasional and casual desire for a topographic carving of the state of California,
where we live, and I thought it might be something I could figure out how to get her. In the end,
after many dozens of hours of work, five weeks, and several hundred dollars paid to a professional
CNC machine shop, I had the artifact shown in the picture above. This is the story of its creation.
# First steps
Before you ask, I did not do a ton of research before embarking on this. As I write this, about six
months later, it only now occurred to me to do a basic search for an actual physical thing I could
buy, and luckily it seems that CNC-carved wooden relief maps of the whole state are not trivially
easy to come by, so, *phew!*
No, my first step was to see if there were any shops in the area that could carve something out of
nice plywood, about a week before the intended recipient's birthday. I found one that was less than
ten minutes away, and filled out their web contact form. They had a field for material, and I said,
"some nice plywood between 0.75 and 1.0 inches thick or similar" (I didn't know exactly what was
available and wanted to give broad acceptable parameters), and under "project description", I wrote,
> A relief map of California, carved from wood. Height exaggerated enough
to visibly discern the Santa Monica mountains. I can provide an STL file if needed.
For some [incorrect] reason that I only later examined, I just sort of assumed that the shop would
have a library of shapes available for instantiating into whatever material medium you might
need. But just in case, I included that hedge about being able to provide an STL file. Needless to
say, that was a bluff.
![the programmer's creed: we do these things not because they are easy, but because we thought they
were going to be easy -- from twitter user @unoservix, 2016-08-05][programmers_creed]
*<center><sup><sub>me, every time</sub></sup></center>*
Also needless to say, my bluff was called almost immediately, and I had the following exchange with the
shop:
> *CNC Shop*: STL can work but I can’t manipulate it, which could save some money. If possible can it
>be exported to an .igs or .iges or .stp format?
>
> *Me*: Yeah, STP should be no problem. Can you give a rough estimate of the cost for 1x2-foot relief carving?
>
> *Shop*: Without seeing the drawings, I can’t give even a close price but in the past they range from
>a few hundred dollars to several thousand dollars.
>
> *Me*: That's totally fair! I'll get you some files in a few days.
As you can see, I leaned even harder into the bluff; my next communication with the shop was nearly
four weeks later. But that's getting ahead of things.
# Meshes and solid bodies
First off, let's talk about file formats and how to represent shapes with a
computer.[^math-computers] I said I could provide an *STL
file*. [STL](https://en.wikipedia.org/wiki/STL_(file_format)) is a pretty bare-bones format that
describes the outside surface of a shape as a set of many, many triangles, each of which is described
by three 3D points. This format is popular with 3D printers, which is how I became familiar with
it.
This type of representation is easy to create and read, but it's not great for manipulation.
# Public data
## From space?
## Thanks, California state!
## In Australia, it's pronounced "g'dal"
## Give it a good smear
# Test prints
# Final cut
# Thanks
[main_image]: PXL_20220723_214758454.jpg "A plywood slab carved with CNC into a topographic representation of California"
[programmers_creed]: programmers_creed.jpg "jfk overlaid with the programmer's creed: we do these things not because they are easy, but because we thought they were going to be easy"
[^math-computers]: I'm pretty sure this is more "represent shapes with math" than with a computer, but
the computer is just helping us do the math and it's more relatable.
