VtuberLab

When you watch your favorite VTubers stream, you will notice something subtle yet powerful, the way their hair sways, earrings dangle, or a cape gently ripples when they move. This isn’t just “extra flair.” It’s a deliberate piece of rigging magic called secondary motion, and it can transform a flat, mechanical VTuber avatar into one that feels alive and dynamic.

If you’ve ever wondered how to give your VTuber accessories that natural bounce, swing, or sway, you’re about to learn the secrets. In this blog, we’ll break down what secondary motion is, why it matters for VTubers, and how to use jiggle bones and avatar physics to add realistic animation to your accessories.

Whether you’re working on a full 3D VTuber model or a 2D Live2D rig, understanding accessory physics can help your character stand out and connect with your audience on a whole new level.

What Is Secondary Motion in VTubing?

Let’s start with the basics.

Secondary motion is the subtle, delayed movement that follows a primary action. Think of it as the “after-effect” of motion. If your VTuber avatar turns its head quickly, the hair strands don’t stop instantly—they follow through with a natural lag. The same applies to clothing, jewelry, or props like tails, wings, or scarves.

Without secondary motion, everything looks stiff and robotic. With it, your VTuber accessories behave more like real-world objects, giving your model more personality and realism.

In animation terms, this is closely tied to physics simulation. Your accessories respond to gravity, momentum, and weight. It’s why a bell on a choker will jingle or why cat ears will bounce slightly after you nod.

Why Secondary Motion Matters for VTubers?

Many VTubers focus first on their face rigging and expressions, which makes sense. But accessories often become the real show-stealers. Here’s why adding secondary motion to them matters:

• Immersion: Small movements make your VTuber avatar feel less like a puppet and more like a living character.
• Brand Identity: A flowing scarf or bouncing mascot charm can become part of your signature look.
• Audience Engagement: Viewers notice detail. Accessories that move naturally spark curiosity and create memorable visuals.
• Professionalism: If your avatar accessories look polished with proper jiggle physics, you stand out from beginners and hobbyists.

Jiggle Bones: The Secret Behind Realistic Accessory Animation

One of the most common tools for secondary motion is jiggle bones.

Think of jiggle bones as invisible skeleton parts attached to your VTuber model. They behave like springs, when your avatar moves, these bones wobble, sway, and settle into place according to how you configure them.

For example:

• Add jiggle bones to hair strands → they sway with head movement.
• Add jiggle bones to earrings → they dangle when you tilt your head.
• Add jiggle bones to a cape → it flows naturally when you walk or turn.

These bones are usually controlled through avatar physics systems in programs like Unity (for 3D avatars), Live2D Cubism (for 2D avatars), or middleware like VTube Studio.

How Secondary Motion Works in Different Avatar Types?

Uncover the secret power of secondary motion across 2D, 3D, and hybrid avatars, and see why mastering it can be the game-changer that separates standout VTubers from the rest.

1. 2D VTuber Avatars (Live2D Models)

For 2D VTubers, secondary motion is mostly controlled through physics parameters. Instead of bones, Live2D uses deformers and physics settings to simulate motion.

• Example: Hair physics in Live2D are controlled with pendulum physics. The farther you tilt your head, the more the pendulum swings.
• Accessories like ribbons or necklaces can also be given physics curves, making them sway naturally instead of moving rigidly.

2. 3D VTuber Avatars (VRoid, Unity, Blender Rigs)

In 3D avatars, you can use bones with physics constraints. Unity, for example, allows you to add dynamic bones, jiggle bones, or spring bones to simulate realistic motion.

Example: A long ponytail in VRoid Studio can be rigged with multiple bones, each responding to motion with spring-like physics. Clothing accessories like scarves, belts, or sleeves benefit a lot from secondary motion since they naturally move as part of your body movement.

Today, creators have plenty of options, VRoid for fast character builds, Unity for physics-rich rigs, TheVTubers for accessible custom models, and even the Phygital, which takes things a step further by pairing your 3D avatar with a real-world figurine. Each approach shows how far 3D secondary motion can go, whether you’re streaming or collecting.

How to Add Secondary Motion to VTuber Accessories?

Let’s break this into a step-by-step process you can follow, depending on your model type.

Step 1: Identify Which Accessories Need Motion

Not everything on your VTuber avatar needs physics. Choose wisely.

• Yes: Hair strands, earrings, necklaces, capes, tails, skirts, ribbons.
• Maybe: Glasses, hats, shoes (not much visible bounce).
• No: Static elements like tattoos, armor plating, or rigid props.

Step 2: Choose the Right Tool

• Live2D (2D models): Use Physics Settings in Cubism Editor. Create pendulum movements for parts like hair or clothing.
• Unity/VRoid/Blender (3D models): Use jiggle bones or dynamic bone plugins (like Dynamic Bone or Spring Bone in Unity).

Step 3: Configure Physics Settings

When setting up motion, balance is key. If your accessory bounces too much, it looks like rubber. If it’s too stiff, it defeats the purpose.

• Gravity: Controls how strongly accessories hang downward.
• Damping: Controls how quickly movement settles down.
• Stiffness: Determines how rigid or floppy the accessory is.
• Collision: Prevents accessories from clipping into the body or other parts of the model.

Step 4: Test, Refine, Repeat

Secondary motion is about subtlety. Test movements in streaming software like VTube Studio, Luppet, or Animaze. Adjust until your accessory feels natural.

Tips for Realistic Animation with Jiggle Bones

Adding secondary motion isn’t just about slapping on physics and calling it a day. Here are some pro tips:

1. Less Is More
   Too much jiggle looks cartoony. Aim for subtle, believable motion.
2. Use Layered Motion
   If you’re rigging hair, don’t just use one jiggle bone. Add multiple smaller bones for strands so movement flows from root to tip.
3. Mind the Weight
   Heavy accessories like metal armor shouldn’t bounce like cloth. Match physics to the material.
4. Collision Is Crucial
   Nothing breaks immersion faster than a necklace clipping through your chest. Always test collision physics.
5. Sync with Personality
   Your accessory motion should fit your VTuber persona. A calm, elegant character might have slower, flowing motion, while a hyper character might have bouncy accessories.

Common Mistakes When Adding Secondary Motion

Even seasoned VTubers make errors when setting up accessory physics. Here are the big ones to avoid:

• Over-bouncy motion: Looks funny but unrealistic.
• Too rigid accessories: They move like cardboard cutouts.
• Clipping issues: Accessories pass through body parts.
• Uniform motion: Hair strands moving all at once, instead of delayed, staggered swings.
• Not testing in streaming conditions: Sometimes physics look fine in the editor but messy during live motion capture.

How Secondary Motion Affects Audience Engagement?

Believe it or not, audiences do notice these details, even if they can’t explain why. When a streamer’s avatar moves realistically, the brain unconsciously connects it with lifelike presence. This boosts immersion and helps fans stay hooked.

For example:

• A flowing cape can make you look heroic.
• Bouncy cat ears can make you look playful.
• Dangling earrings can give you elegance.

Accessories with physics become part of your brand identity. Just like your voice, expressions, and streaming style, they help define who you are as a VTuber.

Future of Secondary Motion in VTubing

Technology is moving fast. Tools like VRM avatar standards and real-time physics engines are making it easier than ever to add complex accessory motion. We’re seeing more AI-driven physics adjustments, reducing the need for endless manual tweaking.

Soon, accessories won’t just move realistically, they’ll interact with environments. Imagine:

• Your scarf blowing when wind sound effects play.
• A magical orb accessory glowing and pulsing with your voice.
• Accessories that respond to music during karaoke streams.

Secondary motion is becoming a playground for creativity, and VTubers who experiment with it early will always stand out.

Final Thoughts

Secondary motion may seem like a small detail, but in VTubing, it’s often the difference between looking like a static puppet and feeling like a living character. By using jiggle bones, fine-tuned avatar physics, and smart rigging choices, you can breathe life into your VTuber accessories, making your model not only beautiful but believable. Next time you design or upgrade your VTuber avatar, pay extra attention to those little movements. Because sometimes, the tiniest sways and jiggles are what make the biggest impression.