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CG Hair Fur workflow in Houdini for VFX and Games | Saber Jlassi's GDC 2017 Presentation
Blizzard Cinematics Senior TD presents at the SideFX GDC booth: custom procedural grooming system for VFX, auto-generating real-time hair cards and Nvidia Hairworks export.
Abstract
A Blizzard Animation Senior TD presents a from-scratch procedural grooming system in Houdini and then converts the result for real-time rendering. He builds hair interpolation by triangulating curve roots into a connectivity mesh and using barycentric coordinates from UVs to blend neighboring guide curves, expanding from roughly 100 guides to 86,000 curves; clumping is achieved by packing each curve's point positions into a string attribute via Python, transferring it to high-res curves and blend-shaping toward nearest 1K/3K cluster guides with a root-to-tip ramp, then mixing large and small clumps with a noise map. Variation comes from length offsets along the tangent and a quaternion-based twist deformer built around each clump guide. For games he auto-generates hair cards by clustering tips, extruding ribbons oriented by a ray-projected scalp surface normal crossed with the curve tangent, then bakes color, normal, depth, occlusion and tangent passes by shooting reflection rays in Mantra, packs all 250 card textures into an 8K atlas for Marmoset, and separately exports a 10K curve set with a spherical-UV connectivity mesh through Maya into NVIDIA Hairworks for real-time expansion and wind.
How to read this
- Category
- Production talk: a Houdini procedural grooming-to-realtime workflow
- Contributions
- A from-scratch Houdini grooming system using root triangulation and barycentric UV blending to expand roughly 100 guides to about 86,000 curves, with clumping, twist, and noise-based variation
- Auto-generation of real-time hair cards by clustering tips and extruding scalp-oriented ribbons, baking color/normal/depth/occlusion/tangent passes in Mantra into an 8K atlas for Marmoset
- Export of a 10K curve set with a spherical-UV connectivity mesh through Maya into NVIDIA Hairworks for real-time expansion
- Context
- Relates to procedural hair/fur grooming and the VFX-to-games asset bridge, presented at the SideFX GDC booth by a Blizzard Cinematics senior TD.
- Correctness
- Studio practice, not peer-reviewed; results are production-proven on the presenter's cinematics work, and the specific counts and bake settings are workflow choices rather than validated optima.
- Clarity
- Dense and implementation-heavy; a first watch conveys the pipeline shape, a second pass is needed to follow the attribute-packing and card-generation details.
- How to read it
- Focus on the guide-to-dense interpolation (barycentric blending, clump string attributes) and the hair-card baking/atlas path; rewatch the relevant section if you are exporting to Hairworks or building cards.
Related work
Keywords
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