Zhuoshi REN's BLOG

In this blog, I want to share my experience building a hinge-like switch for an FK rig, which helped me keep the head stationary while the neck moves. Typically, in FK setups, when the neck moves, the head automatically follows—this can be frustrating when you want more independent control, like in a scene where the head needs to stay in place while the body or neck moves.

I solved this by creating a switch, more like a hinge, which prevents the head from following the neck. I experimented with constraints (particularly using a parent or orientation constraint) to allow the head to maintain its position regardless of the neck’s rotation or movement.

At first, it was a bit tricky to balance the hierarchy, but once I nailed it down, the extra control felt great. This approach gives a lot more flexibility when animating, especially for exaggerated movements, as the head can hold its place or move independently based on what the scene needs.

Overall, it’s a handy technique for creating more dynamic and versatile rigs, and I found it particularly useful in situations where I want the head to stay still while the body moves around it. It’s a small tweak but makes a big difference in character animation.

For this setup, I’m combining FK control with a stretchable tweak widget to create a flexible, highly controllable bendy chain. It consists of four main components: deform bendy bones, mechanism bendy bones, tweak widgets, and the FK chain.

1. Deform Bendy Bones: These are the bones that actually deform the mesh. They allow the chain to bend smoothly, adding natural curvature to the model.
2. Mechanism Bendy Bones: These bones handle the bending mechanics, working behind the scenes to ensure the chain deforms correctly. They follow the main control bones but aren’t directly responsible for mesh deformation.
3. Tweak Widget: This widget gives additional control for fine-tuning. I use it to tweak the chain’s shape, adjusting the stretch and bend for a custom look.
4. FK Chain: The FK part allows me to rotate each bone manually, giving precise control over how the chain moves. It’s essential for more controlled animations where specific bending angles are needed.

By combining these elements, I get a super bendy and stretchable chain, perfect for creating fluid, dynamic motions!

What is FK (Forward Kinematics)?

FK (Forward Kinematics) is an animation technique where I control each bone in a chain manually, starting from the base, like a shoulder, and working outwards to, say, the hand. The movement is predictable since I have to rotate each joint individually. I like FK because it gives me full control over how each part moves, and while it’s more hands-on, it feels intuitive when animating simple, fluid motions like swinging or bending limbs.

In Blender, working with FK means spending time adjusting bones one by one, but the upside is that I know exactly how the movement will flow from one joint to the next.