Hello!
I have the question while using the MoI.
How can I define the units for example mm, inch, cm etc..?

Please , Help me.!~

Hi, right now MoI does not have any way to specify what unit system is being used.

It just uses the concept of a generic unit. You can decide that this is whatever you like, cm, mm, inches, whatever, just as long as you treat it in a consistent manner between different files that you create.

But I do plan on adding in a proper unit system setting like you are looking for fairly soon though.

- Michael

Excuse my ignorance but why would you need this?
Do you want to mix mm's and inches in one model or something?
Otherwise, you can use the units as you prefer...

I for example use the decimals as mm's (so 1,20 is 1 cm and 20 mm) but i could as well say 1,0 is 1 inch.

> Excuse my ignorance but why would you need this?

There are a couple of reasons why I want to provide this:

Saving your choice of units in the file can end up being a useful bit of documentation that makes it easy for others to understand later on what you were considering "1,0" to be.

If you're working with multiple files from different sources and combining things together, having the unit systems set in each one will allow them to be imported into the current model at the proper scale.

And finally, a lot of people are just really accustomed to setting the units. A lot of CAD software makes a big deal about choosing your unit system as one of the first things you do when you create a file. So a lot of people just aren't comfortable or accustomed to the whole "units are what you think they are" method...

- Michael

Hi Michael,

There is probably an obvious answer to this, but if the units aren't defined,
why are they consistent with millimeters and come in with no unit conversion messages popping up,
when I bring a MoI model into Rhino? I've imported models from AutoCAD and other SW's
which were way out of scale.

-Jesse

Hi Jesse - in the .3dm file, MoI sets the units to a special "no unit system" value. It appears that Rhino doesn't have a way to set this in its UI, but it is available to programs writing a .3dm file.

When Rhino imports a .3dm file with this setting in it, it seems to just bring the values over into the currently defined unit system with no changes (with no unit conversion message). So for instance 3.5 will come in as 3.5 mm if your Rhino units are mm.

So it works for you because you are considering MoI's generic units to be millimeters, and your setting in Rhino is set to millimeters too, so they match up.

- Michael