Introduction
Blender’s Smooth Hair Curves geometry nodes preset refines hair strand shapes by smoothing curves, eliminating kinks and jitter for a polished look. It’s used after initial hair generation and styling nodes to gently relax strands and remove jaggedness, saving time compared to manual smoothing. The node provides procedural, real-time adjustments, and is non-destructive. It softens existing strand shapes, unlike Straighten Hair Curves, which straightens strands. Compared to the old particle hair system’s comb smooth brush, it offers a procedural approach with adjustable parameters. It can be combined with Resample Curves for further control over strand resolution.
Understanding Inputs
The Smooth Hair Curves node group comes with several input sockets that let you control how the smoothing is applied. These inputs provide fine-grained control so you can tailor the effect to your needs. Below we explain each input in detail:
Amount Input Socket
The Amount input controls the smoothing intensity. Higher values strongly smooth curves, while lower values apply mild smoothing. Negative values invert the effect, adding kinkiness. Use positive values for grooming, starting moderately and increasing gradually to avoid over-flattening hair. A value of 1.0 provides strong but reasonable smoothing. Small amounts preserve original shape.
Shape Input Socket
The Shape input controls how the smoothing effect is distributed along the hair strand, determining whether it applies uniformly or gradually.
A Shape value of 0 results in constant smoothing along the entire strand. A value of 0.5 creates a linear falloff, where one end (usually the root) is affected more than the other, fading toward the tip. Adjusting this parameter helps preserve specific styling details, such as keeping curly tips intact while smoothing only the upper part of each strand.
This setting allows fine-tuned control over smoothing, preventing over-processing in areas where texture should be maintained.
Iterations Input Socket
The Iterations input controls how many times the smoothing process is applied to hair curves. More iterations result in progressively smoother strands, as each pass relaxes the hair further.
While higher values increase smoothness, they also add computational cost, affecting performance. In most cases, 1 iteration is sufficient, with 2 or 3 iterations used for very jagged hair or ultra-silky effects. Beyond 5 iterations, improvements become minimal while processing demands increase.
For best results, use the lowest number of iterations needed to achieve the desired smoothness while maintaining efficiency.
Weight Input Socket
The Weight input controls how much smoothing is applied to different parts of the hair, acting as a mask or multiplier for the effect. If left empty, Blender defaults to 1.0, applying full smoothing everywhere. Supplying a weight factor—such as a vertex group, attribute, or texture map—allows for localized control over smoothing strength.
This input can be used to smooth specific areas (e.g., the top of the head while leaving bangs untouched) or to create gradual falloff using the Curve Parameter. Lower weights reduce smoothing intensity, preserving details like frizz or wild strands. For advanced styling, plugging in an attribute field provides precise customization while maintaining the overall hair structure.
Lock Tips Input Socket
The Lock Tips input prevents the tips of hair strands from moving during smoothing. When enabled, only the middle and root sections of the strands are affected, ensuring the tips stay fixed in place. This is useful when maintaining a specific hair length or silhouette, such as keeping hair tips touching the shoulders or preserving a styled shape.
If Lock Tips is disabled, the entire strand, including the tip, is smoothed, which may slightly shorten the hair as it straightens. This setting is an artistic choice, depending on whether the tips should stay anchored or be adjusted along with the rest of the hair.
Preserve Length Input Socket
The Preserve Length input ensures that hair strands keep their original length after smoothing. Without it, smoothing may shorten strands as curves straighten. When enabled, the algorithm compensates for this effect, preventing hair from shrinking toward the scalp and maintaining overall volume and coverage.
This setting works well with Lock Tips, where tips remain fixed while strand length stays unchanged, ensuring the hairstyle’s shape is preserved. If a shortening effect is desired, Preserve Length can be turned off to allow strands to naturally relax.
Understanding Outputs
Geometry Output Socket
The Geometry Output carries the smoothed hair curves after applying the Smooth Hair Curves node. It retains all hair data while passing only curve-based geometry forward in the node tree. If the input includes non-curve elements (like a scalp mesh), they remain unchanged.
This output is typically connected to subsequent hair nodes (such as Clump, Set Profile, or Attach Hair Curves to Surface) or sent directly to rendering. The node does not generate additional outputs, as it simply deforms existing curves to refine their appearance.y.
Faster Hair in Blender Using PixelHair 3D Hair Asset Collection
PixelHair is a library of pre-made, professionally groomed hair assets for Blender and other platforms, designed to eliminate the need for manual hair creation and smoothing. Instead of building hairstyles from scratch, artists can import ready-made assets that are fully groomed, optimized, and ready for use.
Benefits Over Manual Grooming
PixelHair provides high-quality hairstyles with natural clumping, frizz, and smoothness, reducing reliance on nodes like Smooth Hair Curves. The assets are built using Blender’s particle hair system, offering realistic strand thickness and materials. This saves time, ensures consistent quality across projects, and allows for faster workflow adjustments without complex node setups.
Future Integration with Geometry Nodes
Currently based on Blender’s particle hair system, PixelHair will be updated to support Geometry Nodes once Blender’s new system is fully developed. This will allow for non-destructive edits and procedural modifications, making the assets even more flexible.
Unreal Engine Integration & Real-Time Workflows
PixelHair can be exported to Unreal Engine as Groom assets via Alembic or converted into hair cards for real-time performance. This ensures high visual fidelity in both Blender and game engines, making it ideal for cinematics, real-time applications, and MetaHuman integration.
PixelHair provides a fast, high-quality alternative to manual grooming by offering ready-made hairstyles that work seamlessly in Blender and Unreal Engine. Whether for offline rendering or real-time projects, it allows artists and studios to achieve professional results with minimal effort while ensuring future compatibility with evolving Blender hair systems.
Frequently Asked Questions (FAQs) about Smooth Hair Curves Node
- When should I use the Smooth Hair Curves node in a hair grooming workflow?
Smooth Hair Curves is a finishing tool in hair geometry nodes, applied near the end of the styling process. It smooths out imperfections left by earlier nodes, such as clumping, curling, or frizz, acting as a “polishing” step. For best results, use it just before finalizing the hair to ensure a clean, even appearance. Placing it too early risks its effects being undone by subsequent modifications. - How is Smooth Hair Curves different from the Straighten Hair Curves node?
Smooth Hair Curves refines hair by removing small irregularities, preserving the existing style. Straighten Hair Curves reduces curvature, straightening hair. Smooth = subtle smoothing, Straighten = significant straightening. Smooth polishes hairstyles; Straighten corrects kinky hair or creates straight styles. - Why do my hair strands become too straight or lose their shape after smoothing?
Over-straightening with Smooth Hair Curves happens from excessive smoothing (high Amount, many Iterations), erasing the intended style. Fix by reducing Amount/Iterations, adjusting Shape for targeted smoothing, or ensuring you didn’t mean to use Straighten. Moderate smoothing shouldn’t remove large curls. - What does the Shape input do on the Smooth Hair Curves node?
Shape in Smooth Hair Curves controls smoothing distribution: 0 is uniform, 0.5 is linear (more smoothing at one end). It adjusts the smoothing falloff. Use it to preserve hair ends/bases. Adjust Shape while viewing strands to get the desired effect. - How can I control or limit where smoothing is applied (using the Weight input)?
Weight input in Smooth Hair Curves uses a mask (field) for targeted smoothing: 1 is full smoothing, 0 is none. Vertex groups, Curve Parameter, and separate hair systems can be used for custom smoothing. Default weight (1.0) is uniform smoothing. - Will smoothing change the length of my hair strands?
Smoothing can shorten hair. Preserve Length in Smooth Hair Curves prevents this, maintaining original hair length. Without it, length reduction occurs, especially with strong smoothing. Use Preserve Length for consistent results. - What is the purpose of the Lock Tips option?
Lock Tips fixes hair tip positions during smoothing, preserving endpoint locations. Use it for straight cuts or to prevent tip movement. It works best with Preserve Length. Without it, tips can be adjusted, creating a softer effect. - Does Smooth Hair Curves work on any curve, or only on hair?
Smooth Hair Curves smooths any curve geometry, not just hair. It works on any curve data, but not meshes. For hair grooming in Blender 3.3+, it smooths strand-based hair (curves). Older particle hair needs conversion. - The Smooth Hair Curves node is slowing down my scene – how can I optimize performance?
Smooth Hair Curves slowdowns result from high hair density/iterations, or heavy node processing. High curve resolution can create excessive points, causing performance issues. To optimize, here are a few strategies:- Reduce Iterations: As mentioned, keep the number of iterations as low as possible. Each iteration multiplies the work. If you only really need a subtle smooth, use 1 iteration.
- Lower Hair Resolution Before Smoothing:If hair strands have many points (high density), smooth at a lower resolution and increase resolution later. A Resample Curves node after smoothing can manage point count. If Smooth Hair Curves increases density, Resample (Length mode or set count) can reduce it.
- Use Weight to Limit Smoothing Area: If performance is an issue, perhaps you don’t need to smooth every strand or the full length of every strand. By using the Weight input to only smooth certain parts, you reduce computation on parts that don’t need it.
- Profile the Node Tree:Slowdowns might be from other nodes, not just Smooth Hair Curves. Check for physics or high instance counts. Mute Smooth to confirm, then use previous optimization tips if needed.
- Hardware and Patience:Very high hair density can still cause slowdowns despite optimizations. Consider reducing density via interpolation.
yes, Smooth Hair Curves can slow down systems with dense hair data. Control iterations, resample, and avoid over-smoothing for better performance. Use minimal settings for acceptable results.
- Where should I place the Smooth Hair Curves node in my geometry nodes setup for best results?
Place Smooth Hair Curves after major shaping nodes, before final output. Late placement smooths roughness. Early placement can be overridden. Typically, place after attaching to the surface. Smooth guides before or after interpolation. Late placement, before rendering, is generally best. Adjust if needed. End-of-chain is a good default.
Best Practices
To get the most out of the Smooth Hair Curves preset and maintain natural-looking hair, consider these best practices in your workflow:
- Use Smoothing Judiciously: Avoid cranking the smoothing to the maximum on all hairstyles. Hair often looks best with a bit of variation and texture. Apply just enough smoothing to remove unwanted jaggies but not so much that the hair becomes overly uniform or lifeless. It’s easier to incrementally increase smoothing than to restore lost detail, so start subtle.
- Combine with Other Nodes Strategically: Smooth Hair Curves enhances other hair nodes like Frizz, Curl, and Clump by refining effects without negating them
- Preserve Style with Weight and Shape: Use Weight or Shape to selectively smooth hair, preserving rough or curly areas. This allows for targeted smoothing and maintains artistic style.
- Lock Tips for Consistent Length:Lock Tips prevents end movement, maintaining length. Use with Preserve Length for uniform haircuts and to avoid shrinkage.
- Check Topology After Smoothing:Check point density after smoothing. Use Resample Curves to fix excessive density and ensure efficient geometry.
- Iterate and Visualize: Use visual aids like viewport overlays or mesh conversions to assess smoothing. Adjust parameters incrementally and inspect the model from various angles. Test renders reveal choppiness under lighting.
- Maintain Organized Node Trees: Organize node trees by grouping related operations and labeling them for clarity. Use sticky note comments to document node functions. This prevents confusion and aids collaboration.
- Leverage PixelHair or Asset Libraries: Utilize pre-made assets like PixelHair to expedite workflows. Apply Smooth Hair Curves to refine imported assets procedurally, combining speed and control.
- Stay Updated with Blender’s Hair System: Keep abreast of Blender’s hair tool updates. Check release notes and manuals for changes to Smooth Hair Curves. Use the latest stable Blender version for performance enhancements and bug fixes.
- Practice and Experiment: Experiment with Amount, Shape, Iterations, and other parameters to understand their effects on different hairstyles. Use test hairs to develop intuition for natural smoothness. Procedural workflows allow for adjustments without permanent changes.
By following these practices, you can efficiently integrate the Smooth Hair Curves preset into your hair grooming pipeline and achieve professional, high-quality results that meet the needs of any project, whether it’s a single character for an illustration or a cast of characters in a studio production.
References & Additional Resources
- Blender Manual – Smooth Hair Curves Node: Official documentation describing the Smooth Hair Curves geometry node, its inputs (Amount, Shape, Iterations, Weight, Lock Tips, Preserve Length) and outputsdocs.blender.org. This is a primary reference for understanding what each parameter does in Blender’s latest version.
- Yelzkizi Blog – Create Hair in Blender: Particle Hair & Geometry Nodes 3D Hair Curves: Article by Yelzkizi explaining Blender’s hair systems. It outlines various preset node groups (including Smooth Hair Curves) and their purpose, e.g. “Smooths hair curves for a cleaner, more polished look, reducing jaggedness.”yelzkizi.org. Helpful for grasping how Smooth Hair Curves fits into a complete grooming workflow alongside nodes like Straighten or Clump.
- Yelzkizi – PixelHair Documentation: Multiple posts on Yelzkizi.org detail the PixelHair 3D Hair Asset Collection and usage. Notably, the PixelHair guide confirms that current assets use Blender’s particle system and mentions plans to update to the new geometry nodes hair when it maturesyelzkizi.org. It also covers the workflow to export PixelHair to Unreal Engine’s Groom systemyelzkizi.org, which is useful for real-time hair.
- Blender Stack Exchange – User Q&A on Smooth Hair Curves: Community discussions where artists troubleshoot issues with Smooth Hair Curves. For example, one user’s question highlighted performance issues when smoothing extremely dense curve data, noting the node produced many points and suggesting use of Resample Curves to optimizeblender.stackexchange.com. Such threads provide insight into real-world use and limitations of the node.
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