00:00We will now build the neck and head rig. So basically what we want is just to have those
00:08two bones to be controllable and it's already the case. But I would like to add a small feature
00:15which is very interesting. It's the fact that the neck and the head follow the rotation of the body
00:22or not. It means that we will have to build this mechanism and also create this controller that
00:29will allow us to whether follow the rotation or not. This is a very important chapter because most
00:37of the complex rig we will see later on will depend on this kind of mechanism where you are isolating
00:46one transform channel such as the rotation, the scale or location. To illustrate it, I've just
00:53built a new rig which is just two bones that are parenting one with each other.
00:59There is a first way to isolate the rotation. If you go in the bone option in the relationship,
01:05you will see the parenting relation. And here we can uncheck inner root rotation, inner root scale
01:12and inner root location if the child is not connected. And we'll have the behavior we are looking for.
01:20And there is a big downside to this. So my advice is you should never ever use
01:28this to create this kind of mechanism. And here is why. If I create a root bone that if this was a
01:36character would allow us to orientate it in the world space, note that whenever I will scale it,
01:44rotate it, the other bone won't rotate at all. It means that this inner root option is absolute. It will
01:54override the whole rig and this is really bad. So I will rename the chain. I will call this torso and
02:02head and I will add again the root bone and parent the torso to this root bone.
02:08This simplified ring will help you to focus on what we are doing instead of working on the whole
02:16character. So now I do have some things that behave like our torso to neck relationship.
02:22So whenever you want to isolate a function like the rotation, you need to create an intermediate bone.
02:30So I will extrude a new bone in the neck area, let's say, and I will call it ENT head for intermediate.
02:40Since I've extruded it, it's already parented to the torso bone. So it follow it. So the trick will be to
02:47create a secondary bone that will copy some of the information of this previously created bone.
02:56And the goal will be to isolate whether the rotation, the location or the scale on this bone,
03:02and then to parent the head. To make our life easier, I will go into the object option of the
03:08armature and in the viewpoint display, I will switch it to wireframe. So here I can see I've made a mistake
03:15while scaling this bone because my origin point was set to median instead of individual origin.
03:23So I will just press control Z and scale it a little bit so that both bones are not one on top
03:29of the other and we can read it properly. I will call this NCH for mechanism head. Since I don't want
03:37this bone to follow the torso, I will just click the cross to unparent it. So now it has no parent,
03:44so it stays still. If I wanted to follow the location of the intermediate bone, I need to select
03:50the intermediate bone, then the MCH bone, press control shift C and add a copy location constraint.
03:58Now this MCH bone is following the position of the intermediate bone, but doesn't rotate. So if I
04:05now parent the head to this bone, it will follow its location, but it won't rotate and it won't follow
04:13the rotation of the rotation of the torso. If I want this MCH bone to rotate, I just need to select
04:20the intermediate bone, then this MCH bone and add a copy rotation. Now it will follow since the
04:27intermediate bone is parented to the torso and this bone is now copying the rotation. The great thing,
04:34the great thing about constraint is that we can dial their influence. So I can switch between I follow
04:41the rotation or I don't follow the rotation. So we now have an option that allow us to switch this
04:49influence. But if I rotate my root bone, I still have the same issue as before. And this is because the MCH
04:58bone is not parented to anything. But if I parent it to the root bone, it will now follow the rotation of
05:07the root bone. As a child of the root bone, it will follow any of its transformation. And as the head is
05:14a child of this MCH bone, it will follow the same rules. What is important to know here is that constraint
05:21will overwrite the parenting. So the parented will somehow append first. And then if the constraint
05:29have to change the way the bone behaves, it will do so. You could then add a copy scale if needed.
05:37Personally, I prefer to not copy the scale of the torso upon the head so that I can control the scale of
05:44the torso and the scale of the head for cartoony effect. So let's get back to our character rig.
05:50I will name a new layer MCH where we will store all the mechanism bone and intermediate bone,
05:57etc. And in edit mode, I will extrude a bone from the base of the neck or the end of the chest as you
06:05want. I will call it MCH Neck Rot. Then I will duplicate it and scale down the duplicated bone.
06:14I will then go in the object display mode to enable the wireframe mode so that we can see through the
06:22bones. I will add the ENT word to my newly created bone to make sure it's the intermediate bone. So
06:31it's just a way of naming things. It doesn't really matter if you give it another name. It's just that
06:37along all the course I will name those intermediary bones this way. So this bone will be parented to
06:44the control torso and then I will parent the neck to this bone. So the neck won't be parented to the
06:52chest bone anymore. As we did previously, I will then select in pose mode the MCH bone,
07:01then the MCH intermediary bone and add a copy location. Then we'll add a copy rotation to this
07:09bone. In this version, I've also added a copy scale, but it's not mandatory and I don't think that it's
07:15very useful. You can rename the constraint. So I will just add a neck follow so that we can easily
07:23identify these constraints. I will double check that the MCH bone is parented to the chest bone
07:31and I will just hide the bone so that we can see clearly what I'm doing. Now our chest is behaving
07:37as usual. The neck is following, but if I reduce the influence of the copy rotation, the neck is no
07:44longer following the rotation. It's really handy for dense animation or run cycles. And you can see that
07:52the neck is following the rotation of the torso. So everything is going fine. So we have achieved our
08:00first complex mechanism, but accessing to the constraint is a bit complicated. So if the animator
08:09have to select the right bone to enable or disable the neck follow, it won't be super handy. What we will do
08:17is that we will create another bone by duplicating the head bone and we will call these bone properties.
08:24And we will store all the properties in this bone that will allow us to enable or disable all the
08:33desired constraints through drivers. And we will see those drivers in the next video.
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