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【Live2D Explanation】Expressive eyebrow modeling method using glue (Patreon)
Content
*This article is a translation of one written on April 2, 2022.
Well, it's April!
Sorry I have a bit of a shoulder injury and have not been able to post consistently.
Well, I haven't explained the details, so I think I'll explain how to make eyebrows this time.
Like this.
Tracking-only, it is possible to produce not only up-and-down and angular movements, but also left-right differences.
This is a nizimaLIVE movement, but it can also be done in VtubeStudio.
This is a parameter. I am using 6 in total.
The "○" marks are parameters that are moved by tracking, the "★" marks are parameters for physics calculations, and
The mark ◇ is the parameter that is moved at the time of difference.
○Eyebrows Upper lower
It is a simple eyebrow up and down movement. I use a deformer to move the eyebrows.
Many people use separate deformers for the left and right eyebrows, but I do them all together because I can't use the movement inversion if I do that.
〇 Eyebrow angle → 〇 Eyebrow angle ←
This parameter is for tracking only. No deformation is added.
VTS used to not allow separate left and right eyebrow tracking, but it has been able to do so since some time ago. nizimaLIVE has had separate left and right eyebrow tracking since the beginning. However, it is more difficult to move them asymmetrically compared to Facerig. (Facerig's webcam is inaccurate and the movement is blurred, so it just looks that way...)
To begin with, Japanese people have a narrower brow range of motion than Westerners, so it is not possible to achieve such cartoon-like brow movements.
Therefore, the asymmetrical movement described above is managed by the movement of the corners of the mouth. How to do this is described below.
★Brow angle→ ★Brow angle←
This is a parameter for physics calculation. This parameter is related to the aforementioned "○ brow angle → ○ brow angle ←". Add a deformation to this parameter.
First, deform the art mesh directly as usual. Deform the eyelashes using deformers to match the deformation of the eyebrows
I think there are many ways to deform the eyebrows, but I make it so that when the value is negative, it becomes an "inverted ㇵ-shape" and when it is positive, it becomes a "ㇵ-shape".
It is very easy to use because you can easily create "angry eyebrows" and "troubled eyebrows" by tracking.
Live2D's default parameters include "eyebrow deformation" and "eyebrow left/right," but I only use up/down and angle for tracking. The current application can only detect eyebrow vertical movement, so I can't fully utilize such detailed parameters. (I use "eyebrow deformation" as a parameter for key presses, though!)
Now, let's go back to the story. If we create "inverted ㇵ-shape " and "ㇵ-shape" separately for the left and right sides in the art mesh, we get this.
Back in Facerig's heyday, many of you had your eyebrow links turned off and had this kind of movement!
It's not bad, but frankly, I think the eyebrow connection when asymmetrical is unnatural.
This time, we came up with a new method to simplify the parameter structure while eliminating this unnaturalness.
But first, let me explain about "◇ eyebrow deformation.
◇ Eyebrow deformation
This is an emotional expression parameter for key press difference. Thus, the shape of the eyebrows in the default state can be changed to accommodate various situations, such as a smug or relaxed face.
In addition, the "★Brow Angle" movement is also created in each state so that the eyebrows move by tracking even when the brow differential is turned on.
The deformation has been largely completed, but the unnaturalness of the eyebrow connection has not yet been resolved. In the past, I used to move the left and right eyebrows with the same parameters because I did not like this unnaturalness. The following tweet is the result of my trial and error to find a better way to achieve the "bad face" of asymmetrical eyebrows.
https://twitter.com/himono_vtuber/status/1331378657202368512?s=20&t=9Na-l541lDE2JQuLl6eT4w
I am freaked out by the passage of time that this video is 2 years old, but I can create a "natural bad face" by interlocking the eyebrow heads left and right like this.
However, this time I am trying to manage even more detailed emotional expression of the eyebrows with key presses, so the above method is a bit problematic.
you want to link the left and right eyebrows, you would type dots for both "★ eyebrow angle →" and "★ eyebrow angle ←," but if you also link them to the key-press parameter "◇ eyebrow deformation," you will have three types of parameters.
Even if you get 9 points, it's nothing if you work hard, but this time we also aim to "make the parameter stringing as simple as possible even if the movement is terribly complicated," so we want to keep it to less than 2 types if possible.
So this time we will use glue.
First, copy and paste the regular eyebrow art mesh for glue.
Then move the associated parameter to the opposite brow parameter. If →, move it to ←, if ←, move it to →.
https://youtube.com/shorts/aOqKauotNKc?feature=share
Then, I set the transparency of the art mesh for the glue to 0% using multikey editing.
In this case, the eyebrow art mesh is multiplicative, so if two art meshes are overlapped, the color will be black. Even if it is normal, the border will be slightly thickened, so it is better to make the art mesh for glue transparent.
Finally, glue together the normal art mesh and the art mesh for glue, and adjust the weights like this.
Green is the "normal predominant" and red is the "glue predominant". (If the colors are reversed when you make a copy, reverse the glue weight as well.)
Thus, by making the end of the brow 100% green weighted to give full dominance to the normal brow, and adding a little red weight to the brow head (not 100%, but just enough to make it yellow), the brow head can be made to move in tandem with the brow head when the opposite brow moves.
When the opposite brow moves, the brow head can be moved in tandem.
Like this! Symmetrical when both have the same movement. Bad face good~!
The deformation is now complete. Now it's time to set up the physics to make this thing work.
The two physics groups are "← eyebrows" and "→ eyebrows".
Four types of input parameters are entered.
○Eyebrows Angle
It is simply the movement of the eyebrows. This will link the tracking parameters to the physics parameters. If you've been following my know-how, you're already familiar with this technique. Let's set the corresponding ones for the left and right eyebrows.
○Eyes Open/Close
Enter in position X so that the eyebrows move slightly when blinking. (Check the Invert box.)
The "Angle" parameter moves more beautifully, but the default value of the eye parameter is not in the middle, so the default eyebrows are deformed by the tilted position when the "Angle" parameter is used. (If we create a parameter for normalization of input, I can input angle, but since it moves beautifully even with position X, I feel that we do not need to go that far this time.)
This is also entered separately for the left and right sides.
★ Eyeball Y
The eyebrows move in accordance with up-and-down eye movements. By placing the eyebrows in the "★ eyeball Y" instead of the "○ eyeball Y," the eyebrows can respond to minute eye movements when the angle of the face is moved up and down.
★mouth X
Enter only "← eyebrows." By doing so, only the ← eyebrows move with the mouth X movement, resulting in a bad asymmetrical face.
It is your choice which eyebrow to move, but when you move it, the eyebrow of the one with the raised corners of the mouth should be lowered. If you move your face asymmetrically in the same way yourself, you will see that the eyebrows naturally move that way. Perhaps you are squeezing the facial muscles of one side.
Incidentally, the "★Mouth X" is marked for physics calculation, but this is because nizimaLIVE has separated the movement of the mouth X from the left and right to force it to move.
When the left and right mouth corners are moving asymmetrically, "mouthX" moves, but when they are symmetrical, it does not move...and so on.
Therefore, when using VTS, it is OK to eliminate this physics entirely and simply move "mouthX" with "mouthX".
...That's all for the commentary!
I can't wait to make the rest of the hair on the model, etc., but I really need to focus on treatment for a while because my shoulder is really hurting and I can't do my daily work.... (I wrote this article after a good night's rest, but my shoulder is still shaking...)
I will share any progress I make on Patreon, so please be patient with me.
Thanks for reading.
