Making Your First Model Part 15
An Explanation of Bones

Before we get started, I want to clear something up.

As MMD evolves, models will also evolve. There are two bones which are virtually required now that were non-existent in the earlier days.

When you look at this model, you will almost automatically notice that there’s only one bone between . . . let me rephrase that . . . There is only one bone present on the X axis below her hips. That is the center bone.

The center bone is located on the X axis and falls somewhere between the model’s thighs. However, this isn’t a constant as seen in the Luka model that comes packaged with MMD.

With her skirt on, it looks like the center bone falls between Luka's knees. Taking off her skirt reveals that there was a bit of an optical illusion going on. However, her center bone is quite lower than most models that I have seen.

Since the days of PMD models, there have been two new bones added which are now considered standard. The mother bone and the groove bone.

While I don’t know enough about animation to tell you what they do, I can tell you where they go. (Model by Michi-K)

Nothing is weighted to the grove, center, or mother bone.

To study what is parented to what, you can select all of the bones in the bone tab and right click on them to select “Copy as CSV”. You could also press “Ctrl + C”.

Once you have it copied, you can paste the information into any spreadsheet program.

When you paste something like CSV data into LibreOffice Calc, it will bring up an import dialogue. If you choose for it to separate cells based on commas, everything will be sorted into nice columns. This is important, because the majority of the cells between the bone and what it is linked to are pretty useless for right now. You can easily select those columns and delete them, leaving you with something like this:

Now, let’s use my good friend Jisho to figure out what the headers mean!

You can DOWNLOAD this spreadsheet. The ZIP contains the file in two formats: .ODS and .XLS

Now, let me point out a few things. The first is that this is taken from an extremely high quality model with a lot of physics. Because of that, there are bones that an average user would have never even heard of. While it would be easier to plop Meiko’s old PMD bone CSV data into Calc or Excel, it would be less useful. As I said, models have evolved. We’d be bogged down with hidden finger bones and we wouldn’t know what is linked to the groove bone!

The second is that if you can’t read Japanese . . . Sorry. Other than the English names, the data is 100% in Japanese. (See the LearnMMD articles about translating Japanese models.)

For someone like me who studied Japanese for five years, that’s no problem. For the most part, bone names use the most basic characters. If you’re willing to learn that 頭 means head that 右 means right, then you should be able to learn the bone names through brute force. (You can read 頭 as head in your head – you just need to know that it means head!)

As a note, writing scripts (“macros”) for spreadsheet programs is pretty easy! If you were willing to copy all of the Japanese names and write out their English names, you could convert all of the bone names in the CSV data to English. If you think you’ll use this spreadsheet a lot to remind you of what goes where, it might be really helpful to do something like that!

Now, enough of that! Let’s use those English headings to explain each box.

Bone name and English name are pretty self explanatory! That is simply the name of the bones. If you have an English copy of MMD, then it is extremely important that you give your bones an English name in addition to a Japanese name. Otherwise, your bones will be “null”. However, even if you have an English version of MMD, you still need the Japanese name. Otherwise, motion data will not work.

Why’s that? Well, let’s open a copy of a motion data in Notepad++.

With all of those NUL characters, it’s a little hard to point out what’s happening! But you can see where I drew a box around the bone names.

The first thing to note is that MMD uses the Japanese names in the data. The English names are there to make your life easier while using the program . . . but they’re useless in the motion data.

The second thing is that you personally can make motion data with the bones named incorrectly. If you wrote the English names in the Japanese box, or if you just mashed your keyboard at random in the Japanese name box, you personally could make motion data for that model. However, there’s a problem. No one else could use your motion data with any other model! Nor could you use anyone else’s motion data for your model.

For bones for special things that aren’t standard, you can name the bones whatever you want. But for the standard bones? They need the correct Japanese name.

In blue is the parent bone.

Let’s talk about the wrist.

The wrist is parent to five bones. However, a parent can only be linked to one bone. Therefore, the wrist bone isn’t linked to anything, as you can see in that picture.

However, you can also see that some bones are linked to something. For example, thumb0_R is linked to thumb1_R.

If a bone is linked to another bone, then the first bone is the parent to the second bone.

Let’s use “fore2_R” as an example.

When you select a bone in the bone tab, it turns red on the model. You can see that this bone is linked to two other bones. The first bone is “fore1_R”. That bone is the parent.

Remember the green box from earlier? This is where it comes in to play. Because “fore2_R” is linked to “fore3_R”, you put the number for “fore3_R” into the “Link To > Bone” area.

However, even though “fore1_R” is linked to “fore2_R”, you still just put the number for “fore1_R” into the Parent box for “fore2_R”. “fore1_R” has “fore2_R” in its “Link to > Bone”.

Now, for the lavender box from earlier. For a basic model, there is only one set of bones that uses that section. Those are the eye bones.  Their “Append Parent” is 両目 (or Eyes or Both Eyes . . .)

The purpose of the “Both Eyes” bone is to rotate around the eyes simultaneously as opposed to rotating both of the eyes one at a time. For the both eyes bone, I had to open up a good model and just copy her bones.

It’s a little confusing, and your eyes will most likely glaze over if you ask a smart person to explain appends! So for now, just know that it’s 100% legal to stare hard at a model and copy their settings!

Now . . . For the part I left out.

IK bones. This is another thing that will make your eyes glaze over. There are tons of tutorials on fixing IK bones . . . Bandages has made quite a few advanced tutorials on IK bones . . . but those made my eyes glaze over too!

So, what can you do?

You can download a model that works well and copy their IK settings, of course!

I feel like I should explain it, but all I can think of to say is that to link the regular bones to the IK bones, you copy the regular bones’ indexes and paste them into the IK Link box. I also know that your IK bone must be in the exact same spot as the target bone.

Other than that? I can’t even look at an IK bone for too long without getting confused!

But for when you decide to copy from a good model, remember something important. A lot of bones are invisible! “toe IK_L”‘s target is “toe_L”. (Remember – it’s hard to find a bone by name, but the number of the target is what’s in the box! Using the number in the box will make it a lot easier to find the bone.)

If, while copying a model’s bone settings, you need to see an invisible bone . . . All you need to do is find the invisible bone in the bone list and click “Vis”. That will make it visible.

However, for IK targets, the Target bones are in the same exact spot as the IK bone. So, that is a little useless in this case!

For leg IK bones, it’s a good idea to study an older model which will be more simple. A newer model may have bones like “右つま先X回転” . . . which I’m sure is important! But it’s not vital.

Let’s open the good ol’ Meiko model to look at her IK bones. The only IK bones she has are the four that are vital to any model: Leg IK left / right and Toe IK left / right.

Let’s take some time to explain the colors associated with IK bones.

A normal bone is a pretty, pale blue. A normal bone that is linked to an IK bone is yellow. An IK target is pink. An IK bone is red.

A yellow bone is set up just like any other bone, and pink bones are almost identical to other bones. The main difference is just that a pink bone is usually set to invisible. Is it so people don’t mess with it? Is it just to make things look nice and tidy? I don’t know! I do know that regardless of if you make it visible or invisible, it will still be pink.

And red bones? Well, like I said earlier, they’re confusing! But if you have MMD, then you have quite a few extremely basic models to base your IK bones on!

Sorry for another chapter that simply explains things! But look on the bright side . . . You won’t have to hear it next time!

Tune in next time for when we add bones!