HairFlow
About
What is HairFlow?
HairFlow is an addon to animate Blender’s new hair system. It works with any curves object, whether the hairs are only generated through modifiers or are finished hair without any Geometry Nodes. It can simulate any hair length but is primarily intended for short to medium-length hair due to (current) collision limitations.
How does it work?
The simulation is based on Blender’s new simulation node system. It is able to animate every single hair strand while still respecting the original shape of the hair. You can animate as many hairs in your scene as you want and control all physics settings directly in the modifier independently.
Simulate Wind Effects
Simulate wind effects on all hairs you want and control the strength and turbulence independently.
Change the Gravity
Want to make space shots? Then just decrease the gravity, and your hairs will go up. Or increase it, and your hair will fall down more strongly.
Better Control
If needed, you can apply two different physics settings for different hair parts, like shorter and longer sections, to have more control over the output. This can be very helpful for more flexible ponytails or to address problematic hair parts with more settled settings.
Hair Collision
It is possible to select a collision object to which the hair will react. One for the head/main part and also an additional independent object. However, the selected objects can only slightly influence the course of the simulation and currently only serve to fix smaller problems. You can also influence the collision reactivity with a separate slider, but if you set it too high, it can quickly result in shaking hair.
Include Objects
We wanted to go a step further and solve another very annoying problem with hair curves. HairFlow also gives you the ability to attach up to two objects to specific points on the simulated hair, which will move and rotate with it. This allows you to attach items like hair ties to the hair, enabling them to dynamically move with it.
Simulation Speed
Play with the physics settings and make them your own. You can even control the responsiveness of the hair. So you can decrease the simulation speed for underwater shots or increase it for more reactive hair.
Realtime Feedback
Even with many hair strands, the addon can perform quite well. But if it gets too slow, you can activate a proxy hair with just one click, which replicates the appearance of the original hair but outputs a reduced number of hairs for a faster inspection of all changes.
Does it work on animals, etc.?
Yes and no. It can animate every curves object, whether it is hair or fur, but it has one limitation: The simulation needs a reference point to calculate the movement and resulting deformation of the hair. This can be either an object or a specific bone of an armature. If you only have one hair system for the whole animal, you can only select one reference point. This means that if you select the torso of the body, for example, the hair will move in accordance with the movement of the torso. However, if you only move the arm, the hair would not move. You could, however, split it into several hair systems for each body part and then select a suitable reference point for each one. Here you can see a test scene from the Cosmos Laundromat Demo by Blender Studio (CC BY 4.0 License). The particle systems were converted to hair curves and then animated with HairFlow.
Here another examples with simulated fur, this time on my Fuzzy character.
Bake It
You can bake the simulation natively under the Physics Properties tab. Keep in mind that the simulation data can take up several gigabytes per shot (which will also increase RAM usage accordingly) because Blender currently doesn´t support compressed baking files for geometry-nodes-based simulations. This will hopefully be added soon in an upcoming Blender version.
License Note
The example hairs were created by Daniel Bystedt (CC-BY-SA License), sourced from the Blender demo files page, and entirely made with Geometry Nodes. The sheep scene is from the Cosmos Laundromat Demo by Blender Studio (CC BY 4.0 License). The particle systems were converted to hair curves and also completely animated with HairFlow.
Teaser
Tutorial
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