V-Ray Tip: V-Ray MultiMatte: Compact RGB ID Masks for Precise Compositing

Use the V-Ray MultiMatte render element to generate clean, lightweight RGB masks for precise compositing without bloating your EXRs.

• When to choose MultiMatte:
  • Best for a small, known set of IDs (fast and compact).
  • Ideal for advertising, product, archviz, and shots with locked asset lists.
  • Prefer Cryptomatte for high asset counts or frequent revisions; stick with MultiMatte for minimal storage and deterministic ID control.

• Setup steps (any DCC with V-Ray):
  • Assign unique Object IDs or Material IDs to assets you plan to isolate.
  • Add a MultiMatte render element. Choose the ID type (Object or Material) and map up to three IDs into the R, G, and B slots.
  • Create multiple MultiMatte elements if you need more than three masks.
  • Name elements clearly (e.g., MM_Obj_A_Red, MM_Mat_Glass_Blue) to keep comp organized.

• Anti-aliasing and edge quality:
  • Enable “Consider for Anti-Aliasing” (or equivalent) so matte edges match the beauty pass.
  • Use the same image sampler settings as the beauty; mismatched AA causes haloing in comp.
  • Avoid clamping on matte passes; clamping can alter edge precision.

• Denoiser and color management:
  • Do not denoise ID mattes. If your DCC offers “Denoise render elements,” disable it for MultiMatte to keep masks crisp.
  • Save MultiMatte to 16/32-bit EXR as non-color data. In comp apps, flag them as “data” (no color transform/OCIO).
  • Keep your beauty in ACEScg/linear, but treat mattes as utility channels to avoid gamma shifts.

• Compositing workflow tips:
  • Extract R, G, or B as individual mattes; optionally invert for quick isolation.
  • Use mattes to drive targeted corrections (hue, levels, relighting) while preserving global grading.
  • For semi-transparent objects, prefer Material ID (often more predictable through glass) and validate edges.

• Organization and scalability:
  • Reserve color channels per department or asset type (e.g., R for architecture, G for props, B for foliage).
  • Document ID assignments in your shot spreadsheet; consistency prevents conflicts between episodes/shots.
  • If assets share a material but need separate mattes, switch to Object IDs or split materials logically.

• Troubleshooting quick checks:
  • Aliased or fringing edges: verify AA settings on the element and sampler thresholds.
  • Wrong mask: confirm ID type matches what you assigned (Object vs Material ID).
  • Missing transparency detail: check if “Affect channels” settings on materials/lights are interfering; test with Material IDs.

Pro tip: Pair a compact set of MultiMattes with a single Cryptomatte for safety. You’ll keep EXR size small while retaining last‑minute flexibility.

Need licensing, expert advice, or upgrades? Explore V-Ray solutions at NOVEDGE. For tailored pipeline guidance and current promotions, reach out to the NOVEDGE team.