Creating a Cartoon Character in Cineversity Brand ID: Rigging Octopus Tentacle Using IK

Photo of EJ Hassenfratz

Instructor EJ Hassenfratz

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  • Duration: 09:53
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In this video we’ll create joints, apply and IK Tag, and then Bind it to our tentacle geometry and quickly smooth the weighting of our object.

In this video we’ll create Joints, use the Naming Tool, apply IK Tags and create Goals, and then Bind it to our tentacle geometry and quickly cover the Weight Manager and how we can smooth the weighting of our joints.

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In this video, we're going to set up our octopus character geometry for animation by rigging it up with joints. We're going to apply in IK tag and bind it to our tentacle geometry and quickly smooth the weighting of our object. So, this is going to be a fairly simple rig, kind of like a crash course into rigging. And fortunately enough for us, the only element that really needs rigged up on our character are the octopus tentacles. So what we're going to do is build up, like, a bone system or joint system that we can then use to deform this piece of geometry. So, what I'm going to do to create some joints or bones is go into my front view, so I can just constrain how I'm laying down my joints. And to create joints, we're going to go to Character Joint Tool, and I'm going to hold down Command and click at the very top of the tentacle here and then Command+Click at the very bottom. And you'll see we just created one big joint, and to create one joint, you actually need two joints, so it's kind of like to create a line, you need two points, so that's kind of like what's happening here. So we got two joints going on but really one big joint here. And we're going to need a lot more joints than this to be able to define the bending of our geometry. So it's kind of like how you need a highly subdivided mesh to be able to bend it and for it to still stay smooth when you actually bend that object. So we're going to do the same thing here, give it a little bit more subdivisions here. And to do that, we're going to hold down the Shift key and just click and give this bone a little bit more subdivision here, so something like that. And you can see we just create a whole bunch more joints. So now what we can do is create a rig where if we move these objects, you can see that this is just traditional animation. You move one object, and it affects everything underneath it in the hierarchy. And this is actually called forward kinematics. What we actually want to do is do inverse kinematics. So instead of moving and affecting everything below it, we actually can control this one joint and move everything before it. So to do that and set up some inverse kinematics, or IK, we're just going to select the first joint in our joint hierarchy, go up to the Character menu, go to Commands, and go to Create IK Chain. Now two things are going to happen. Number one, we now have an IK tag applied to our joint, and in our IK tag, we can see that this automatically defined the end of our joint chain for us, and it also created a goal. Now, notice what happens when I select this goal null here and move this joint chain. You can see it's bending and acting almost as if it's an arm, and you can see that as I'm moving this joint goal, it's affecting everything before it. And that's the inverse of how we were doing it before when we're selecting one joint and, you know, rotating and affecting everything underneath it. So this is a way more efficient way to work and do character animation. Now, the one thing we can do with this, if I go into my perspective view is I can actually change where this is bending. So if I go on to my IK tag, you can see by default our tentacle. It's almost like if the tentacle had an elbow. It's facing in the positive X. Now, where this is bending towards, the direction this is bending towards is called the pole vector. And since we don't have an object defined for that pole vector, we can actually just use this twist. So, say we want this to bend towards us. We can just simply adjust this twist 90 degrees and you can see that now it's bending forward. So you have a lot of control over where this kind of elbow of this tentacle's pointing by adjusting the twist of the pole vector. So you can set this up the way you want. I think I'll just leave this at 90 degrees. And the one thing I want to do before we move any further is we can barely see this joint chain, it's kind of getting hidden by the actual tentacle geometry here. So the one thing we can do to actually see through this piece of geometry and see more of our joint chain is going to our tentacle objects Basic tab and going and clicking on X-Ray. And now we can use our Superman X-ray vision to see through our tentacle object here. So now we can have a much better idea of what's going on with our joint chain. Now, as I'm moving this around, you can kind of get lost as to where this original joint goal started at. Now, what I'm going to do is just hit Undo a bunch of times. And just get that back to its original position and actually undid the X-rays, so I'll just turn that back on again. And let's just keep undoing so we get back to that original point. And you can see that this is, you know, this is part of the trouble here because I'm undoing a bunch of stuff that I did. And what I want to do is just make it so this original position is stored somewhere so I can always go back to it. And I don't have to always do a whole bunch of undoes like I just did which is the wrong way to be doing this stuff. So what I'm going to do to be able to store all these values and just zero them out is to freeze this transformation. Now, I'm just going hit Freeze All, and you can see that that stores all those odd numbers in our coordinates manager here and freezes them down here on the Freeze Transformation area. Now, what this allows us to do is, you know, we can mess around with the actual position of this goal as much as we want and instead of me going, "Oh, no. I actually need to go back in that original joint goal position." And just start hitting undo a bunch of times like I just did. We can actually just zero out this coordinates, and we're back to its original starting position. So Freeze Transformation's very useful, very important when doing character work in working with IK. So I can move this as much as I want. I can rotate this, move this all around and then simply just zero this out or hit Reset PSR. Now, I have reset PSR docked in my menu here because I use it so much for character work. And we can actually find Reset PSR really quickly by hitting Shift+C, bringing up the Commander and just typing in reset, and that'll bring up our Reset PSR, and we can click it that way. Or you can dock it like I did. All right, so we have our IK tag moving. We have that relationship. We have that goal. It's bending our joints, but we need to build that relationship between our joints and the actual geometry here. So to built the relationship between the joints and having them actually deform the object here, our tentacle geometry, is called binding. So we've got to bind these joints to the geometry. And how we do that is by selecting all the joints we want to bind and then selecting the objects we want to bind that joint to which is this tentacle object. And then all we have to do is go to Character Commands and Bind. And what that's going to do is create this skin object and a weight tag. Now, if I click on the weight tag and double click on it, you can see that this is actually a visualization of how each of these joints are affecting each part of this geometry which is really cool. So what I'm going to do is just move this goal, and you can see we have this really nice bending happening. We actually have our joints deforming our geometry through the skin object and using this weight tag. And the one thing you're going to notice is that we have some odd bunching up here, and it almost looks like a thumb if you curl your thumb or your finger. We have this nice folding happening, but we actually don't want that in this instance because we want a smooth tentacle. So to fix that, we're going to blur the weight influence of all of these joints here because you can see that the gradation is not as smooth as it could be. So to do that, we're going to go and we're going to hit Shift and double click on the Weight tag. And this will bring up our Weight Manager, and this has a lot more functions here that we can use to help fix our issue here. And we're just going to select all of our joints. You can see that, again, if I click on all these joints, we can see that influence, and we can see that the gradation is not smooth at all. It's rather choppy. So what I'm going to do is select all of my joints and in the Mode, we actually have this Smooth command. And what I want to do is just smooth out the gradation and smooth out the weighting between all of these joints and hopefully smooth out this folding we have here. So with all my joints selected and with Smooth Mode active, I'm just going to hit Apply All. And you're going to see that just by hitting it once we smooth it out a little bit, but we actually need to go a little bit further and maybe hit Apply All a whole bunch of times until we don't see any more of that kind of folding happening. You know, I think if we hit it about 10 times that should be good. I think we kind of smooth everything out really nicely. So now if I move my goal here, we can see we have this really nice, smooth tentacle bending here, and that's looking a lot better. So, to recap, we set up our joints, bound them to our geometry and then applied smooth weighting to our octopus tentacle. In the next video, I'm going to show you how you can apply dynamic forces to our IK chain to make it look like our octopus is swimming underwater.
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