Creating a Cartoon Character in Cineversity Brand ID: Animating Octopus Tentacles Using IK Dynamics

Photo of EJ Hassenfratz

Instructor EJ Hassenfratz

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In this video we will apply real world physics to our IK via IK Dynamics to replicate the movement of the tentacles moving through water.

In this video we will apply real world physics to our IK via IK Dynamics to replicate the movement of the tentacles moving through water.



In this video, we're going to use our IK rig we set up in our previous video and apply Dynamics to the IK so we can add generative fluid motion to the tentacles and make them look as if they were moving and propulsing through water. So I'm just going to hit play here and I have just set up a couple of Vibrate tags to just make this octopus character just bob up and down, no key frames used, just a Vibrate tag. And you can see that I have all four of my tentacles here. And I just duplicated that initial one we made in the last video. And I'm just going to select all of these IK tags, and just navigate to the Dynamics tag. And what I want to do is go ahead and just check on enable to our Dynamics. Now nothing's really happening right now, but if we just stop this simulation, this bobbing up and down from our Vibrate tag and just kind of move this character's head to the side, you can see that we have Gravity affecting our IK chain here, which is really cool. So I'm just going to undo that rotation that I just made and go back into all of my IK tags. Now the one thing that's really going to help sell the look of our octopus being underwater is adjusting the Dynamic Gravity. So this is our default value of negative 9.81, and what we're going to do is have less Gravity applied to this because underwater stuff has very little Gravity applied to it. You just kind of float around, kind of like you're in outer space or something like that. So what we're going to do is change this Gravity value to a negative 1, and just by doing that, you're going to see that our limbs here, our tentacles are floating a little bit more freely because they don't have as much Gravity weighing them down. So you can much more visibly see the effects of the Dynamics here. So the two options in this Dynamics tab here that are really going to affect and make it look as if these tentacles are propulsing underwater are the Drag and the Rotation Hold here. So the Drag basically adds resistant friction forces and the higher the value, it looks like they're floating through water. And you can see that if I just move this Drag value to about 50, we have a little bit of a propulsion action happening. And this Rotation Hold, which is basically this controls how much our joints try to maintain its original joint chain rotation. So the lower the values, the more they kind of just flop around but the higher the value, the more they want to stay restricted to their original rotation here. Now what I'm going to do is just relax the strength, the overall strength of our Dynamic effect. So the lower the value, the more loose our simulation is going to be. And you can already see that with the strength of five, we have much more fluid motion. So last thing to cover is this Position Hold. So the Position Hold controls how much the joints maintain its original joint chain position. Now look if you have this too low, our joints are just going to fall down to the ground, but if we have a little bit lower value than say 100, maybe 85, you can see that this adds a nice little squash and stretch movement to our tentacles here. Now the one thing that's really going to help accentuate this propulsion effect is by adjusting these Drag and Rotation values even higher. So you can see that once I move these up from 50 to say about 75 each, you can see that the propulsion effect of the tentacles is way more pronounced, and this is without any key frames whatsoever, which is the really great part about this. So the next thing I want to cover is the Curves. Now what the Curves allows you to do is alteract more how the Dynamics strength of the Rotation and Position Holds are applied throughout your joint chain. So the left most point on this Curve is the beginning of your joint chain, or in our instance, the top of our joint chain, and the right most point is the bottom, or the end of our joint chain. So say we want less movement in rotation on the top joints of our joint chain, I'm just going to bring down this Curve editor and you can see that the top of our chain is trying to stay stationary. And we can just CMD+click another point in here and adjust that even more. So you have a lot more fine tuned control over the Position and the Rotation values here. So if I do the same thing with the Rotation, I'll just CMD+click again and create an extra point and then bring down this Rotation Hold. You can see that the top of our IK chain is rotating less. And if I move this even further over to the right, you can see that now only the bottom is rotating and this kind of looks kind of weird, so just be careful with how you're applying this throughout your joint chain, but this allows you to kind of alteract how the Dynamics are applied across the length of your joint chain which is really awesome. So in this video, we applied real world physics to our IK, using IK Dynamics to replicate the movement of the tentacles moving and gliding through water. Now in the following video, I'm going to briefly cover how you can prevent your tentacles from intersecting each other using IK colliders.
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