V-Ray Tip: Convert Curve Networks to V-Ray Hair Primitives

Turn complex curve networks into render-efficient, stylable strands by rendering them as V-Ray hair primitives.

Why convert curves to hair primitives:

• Performance: Hair primitives stream efficiently, using far less memory than mesh extrusions for cables, wires, filaments, grass, and fine details.
• Quality: True hair shading delivers correct anisotropic highlights, glints, and backlit translucency.
• Stability: Robust motion blur, DOF, and anti-aliasing compared to ultra-thin meshes.
• Scalability: Easy LOD through segment count, width clamps, and per-camera tessellation.

Quick workflow (DCC-agnostic):

1. Prepare curves
   • Clean up and reduce CVs where possible to avoid over-tessellation.
   • Ensure consistent curve direction (root → tip) to keep shading coherent.
   • Add per-curve width/radius data if your DCC supports it.
2. Enable hair rendering for curves
   • Maya/C4D/Houdini: Enable “Render curves as hair” (or equivalent) in V-Ray render settings.
   • 3ds Max: Convert splines to supported hair/groom guides or use VRayFur/Ornatrix/Hair&Fur; export guides as hair.
3. Assign a hair shader
   • Use VRayHairMtl/VRayHairNextMtl for physically-based tint, melanin, and dual spec lobes.
   • Drive root-to-tip color/opacity with VRayHairInfoTex and ramps for natural variation.
4. Tune width and tessellation
   • Set root/tip widths; clamp a minimum screen-space width to avoid flicker on sub-pixel strands.
   • Use view-dependent segments where available; keep segment count just high enough to avoid kinks.
5. Lighting and render settings
   • Hair is specular-driven: check highlights under area lights and HDRI.
   • Enable transparent shadows where needed; clamp Max Ray Intensity to curb fireflies on bright emissives.
   • For motion blur, increase hair MB segments if fast-moving.
6. Cache and exchange
   • Publish as Alembic curves or .vrscene hair for cross-app consistency and renderfarm stability.

Shading tips:

• Use melanin-based controls for believable tones; add slight randomization per strand for realism.
• Shape primary/secondary spec lobes to balance broad sheen vs. tight glints; small roughness changes go a long way.
• For thin synthetics (wire insulation, fishing line), lean on transmission/backlighting for credible silhouettes.

Performance checklist:

• Prefer hair primitives over mesh extrusions for thousands of strands.
• Reduce far-distance density via culling/LOD and per-camera segment limits.
• Use the V-Ray Denoiser judiciously; hair benefits from slightly higher AA instead of aggressive denoise.

Troubleshooting:

• Shimmer/flicker: raise AA, clamp min hair width, and reduce extreme specular values.
• Jagged bends: add a segment or smooth tangents only where visible.
• Blown highlights: enable clamping or lower light intensity; avoid overexposed glints.

Ready to try it? Get V-Ray and companion grooming tools at NOVEDGE. For upgrades, bundles, and advice, talk to the experts at NOVEDGE and keep your pipeline efficient from curves to final pixels.