2D Animation: How to Build and Animate a Smooth Rotating Hemisphere Rig

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This post is the second part of the “Exercises With Circles And Ellipses For Beginners” series. You can refer to the first part (Super Easy Exercises for Beginners) for an introduction to using circles and ellipses for getting started with your 2D vector cut-out animation adventures.

In this post, I’ll show you how to quickly build a basic Hemisphere Rig for your 2D digital cut-out animation toolbox.

The Hemisphere Rig gives you a 3D-like look with its smooth 360-degree rotation.

GIF - Rotating Hemisphere

You can use the basic rig as is, or you can customize it in many ways to get even better results.

In my opinion, this Hemisphere Rig is even easier to build than my Fish Rig and Spaceship Rig. That’s true, at least judging by the total number of drawing layers.

Ready? Let’s go build your very own 2D cut-out Hemisphere Rig!

How to Create a Simple 2D Animated Hemisphere Rig

Note that the demo uses Toon Boom Studio, but other 2D vector animation software tools should work just as well.

First, watch this YouTube video to get an overview of the rig:

Step 1: Create the Drawing Layers

The basic version of the Hemisphere Rig pretty straightforward to assemble.

This rig is made up of only 3 drawing layers. The Base of the hemisphere is a full circle. The Dome has 2 sides, which are 2 semi-circles.

To maintain consistent drawing sizes among the 3 layers, simply copy the full circle drawing from the Base layer. Then, paste the circle into one of the Side drawing layers. Split the pasted circle into half using the Scissors Tool. Cut and paste one half of the shape into the other Side drawing layer.

You should end up with the following drawings in 3 separate layers:

Hemisphere - 3 Drawing Layers

Step 2: Set the Key Poses (Keyframes) to Create a 360-Degree Turnaround Cycle

My recommendation for a basic setup is to have a 360-degree turnaround cycle. So your hemisphere’s key poses will follow a sequence like the one listed below:

  1. Side View 1
  2. Bottom View (the Base)
  3. Side View 2
  4. Top View (the Dome)
  5. Side View 1 (return to initial view, identical to pose #1)

You can start with any of the above views, but you must end with that same initial view.

You can also set the sequence in reverse, although the rotation direction doesn’t really matter for your rigging purposes.

The important point is to correctly create the key poses so that your 2D animation software can automatically create the in-between frames for the transition animation sequences.

Here’s a screenshot of my rig with 5 keyframes along the Timeline View:

Hemisphere - 5 Keyframes

Setting the key poses simply involves collapsing or squashing the drawings until they are no longer visible.

Just completely flatten the drawing layers out and you’re done. It’s that easy!

Use maximum zoom to make sure that the drawings are completely flattened.

You may need to adjust the z-depth positioning of the layers to get the right drawing layer to show.

For example, if you see that half of the Base layer is mistakenly covered by one of the Side drawings, nudge that Side drawing back in z-position. For best results, do this while you’re in maximum zoom setting. Do your adjustments in the keyframes only, not in any of the in-between frames.

Follow the steps shown in the video to complete the rotation cycle.

Once you’re done, sweep back and forth through the Timeline View to check for errors. One common error is the appearance of a fine crack between the Side 1 and Side layers, resulting in the Base layer showing through as a fine line. If that happens, nudge one of the Side drawings closer to the other Side layer.

Finally, save your rig in a library for reuse in future animations.

 

Hemisphere - Feature Pose 2

 

Here are the secrets behind this trick:

  1. Recognize the minimum and maximum (sometimes misspelled as maximun, and I have proof) dimensions of each view. For example, when Side 1 is in full view, you see a complete semi-circle, but both the Side 2 and the Base drawings are completely non-visible. In this pose, Side 2 is in the same size and orientation as Side 1, but hidden behind Side 1. The Base is facing left (or West) so it collapses into nothing.
  2. All of the 4 key poses listed above are critical and must be in proper sequence. So if you want to animate your hemisphere rocking back and forth like in the exercise/example below, you need to include 3 poses each time the hemisphere moves in one direction. That is, you need to save and copy 1 intermediate (in-between) pose, plus the key pose (keyframe), and the other in-between pose on the other side.

Using the Hemisphere Rig In Your 2D Animation

Once you have the rig completed, you can use it in your animation by selecting the poses that you like (key poses or in-between poses), copying and pasting them along the Timeline according to your scene plan.

If you’re using an in-between pose, set it as a new keyframe before copying and pasting (at least this is how things work in Toon Boom Studio).

If the transition goes through a keyframe, you need to include that keyframe in the set of sequences that you’re copying.

So basically, when you’re actually using the rig in your animation scenes, you’re not using all of the keyframes. You’re just choosing and grabbing only those keyframes that are useful to your scene to add a little sense of depth.

Adjust the speed of the turn by adjusting the distance between your new keyframes. The closer they are together, the faster they play.

As exercises, try recreating the following scenes using your hemisphere rig:

GIF - Hemisphere Short Sequence

GIF - Hemisphere Animation Sequence

Now reimport your rig into a new scene, then scale down the height of the dome. Run your rotation/turnaround loop and see what happens. Try recreating the following “runaway boat” sequence:

GIF - Runaway Boat

 

Improving Your Hemisphere Rig

For those of you who are geometry experts, you probably realized that the rig’s rotation speed is actually non-linear or non-uniform. It’s a subtle issue, but if you’re really going for accuracy and a little bit more realistic turnaround, you may want to improve this aspect of your rig.

You can fix this by setting the proper acceleration and deceleration functions of each keyframe. However, this is out of the scope of this post. I’m hoping to publish a future post to cover this topic. I’ll update this post and add the link to that post when it goes online.

Conclusions

It only takes three drawing layers, all made of circles, and four unique keyframes to create the 2D trick hemisphere rig.

That’s a piece of cake! And like I’ve said before, you’ve gotta love them circles!

Before long, you’ll be creating cool head rigs with the same kind of smooth 360-degree turns. We’ll do much better than my Toon Baby head rig below! How about that?

If there is sufficient interest, I’ll share the secrets to my Head Rig for FREE!

Please help let me know that my efforts in sharing more secrets and tricks are worthwhile. Click below to join my mailing list so I know you’re interested:

One last thing, please feel free to share this post with a friend or family member who’s trying to get started learning animation on their own.

HAPPY CREATING!

 

 

 

 

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