V-Ray Tip: V-Ray Velocity and Cryptomatte Motion-Blur Workflow for Compositing

Speed up approvals and keep creative control by rendering V-Ray’s Velocity and Cryptomatte AOVs, then applying motion blur in comp. This approach is fast, reversible, and ideal for shots that may need re-times or last‑minute isolation tweaks. If you need licensing, upgrades, or workflow guidance, the team at NOVEDGE can help you get set up with V-Ray and best practices.

Why use Velocity + Cryptomatte for motion blur in comp:

• Iterate faster—tune blur strength without re-rendering beauty.
• Fix edge contamination—Cryptomatte gives clean mattes around fast movers.
• Handle re-times—vector blur can adapt to speed ramps with proper scaling.
• Reduce render risk—shorten 3D render times, push look-dev to compositing.

V-Ray setup checklist:

• Enable motion blur in your render settings and camera. For deforming objects, raise Geometry Samples above 1 to generate accurate per-vertex vectors.
• Add Render Elements:
  • Velocity (VRayVelocity) for motion vectors.
  • Cryptomatte (VRayCryptomatte) for precise object/material mattes.
• Velocity tips:
  • Work in linear color and save EXR (16-bit half or 32-bit float) to preserve vector precision.
  • Match shutter parameters in 3D to your intended comp scale (e.g., 180° shutter ≈ 0.5 frame exposure).
  • Clamp or set a sensible max velocity to avoid extreme values that cause streaking.
• Cryptomatte tips:
  • Choose ID type based on your comp needs (Object/Node name for per-asset control, Material name for surface-driven tweaks).
  • Set Levels (depth) to 6 or higher for dense scenes; keep naming consistent for stable ID hashes.
• Output: Use multi-channel EXR with lossless/near-lossless compression (ZIP/PIZ), keep metadata, and ensure all AOVs are in the same file for robust handoff. If you need procurement or advice on EXR workflows, contact NOVEDGE.

Compositing workflow (Nuke, Fusion, After Effects with ProEXR/Cryptomatte):

• Read the EXR, confirm linear working space.
• Unpremultiply the beauty before vector blur, apply VectorBlur/MotionBlur using the Velocity pass, then premultiply again.
• Adjust scale to match your shutter; start with a value equivalent to your 3D shutter and fine-tune visually.
• Use Cryptomatte to:
  • Isolate movers and avoid background bleeding at edges.
  • Create per-object/per-material blur strengths (e.g., crisp props, heavier blur on vehicles).
  • Build clean holdouts for layered comps and realistic overlaps.

Troubleshooting:

• Streaky artifacts: Lower max velocity or clamp vectors; confirm shutter alignment between 3D and comp.
• Edge fringing: Always blur unpremultiplied; use Cryptomatte edges for proper coverage.
• Deformation flicker: Increase Geometry Samples; ensure moving deformations are enabled for motion blur.
• Re-times: For heavy time-warps, re-generate vectors at the new frame rate when possible for best fidelity.

Pro tip: Keep a “no-blur” beauty, Velocity, and Cryptomatte in a single layered EXR for every shot. It future-proofs your comp and avoids re-renders when editorial changes land late. For V-Ray licensing, renewals, or expert guidance on AOV pipelines, start with NOVEDGE or browse V-Ray options at NOVEDGE: V‑Ray.

You can find all the V-Ray products on the NOVEDGE web site at this page.