Rhino 3D Tip: AOV-Based Render Pass Workflow for Rapid, Non‑Destructive Compositing

Use render passes (AOVs) to separate lighting, materials, and masks so you can iterate looks quickly without re-rendering.

Why use render passes/AOVs

• Speed up iterations: tweak exposure, reflections, and colors in post instead of re-rendering.
• Non-destructive workflow: isolate elements with masks to keep creative options open.
• Consistent deliverables: standardize a pass set across projects and teams.

Core passes to enable (and why)

• Beauty/Combined: your baseline image.
• Diffuse/Albedo: color without lighting—perfect for targeted color correction.
• Direct/Indirect Light: balance key light vs. GI in post for mood control.
• Reflection/Specular: adjust highlight strength and glossiness without artifacts.
• Refraction/Transmission: refine glass and plastics independently.
• Emission: boost screens/LEDs without blowing out the scene.
• Shadow: deepen or soften contact shadows with Multiply.
• Ambient Occlusion: add subtle grounding using Multiply at low opacity.
• Z-Depth: add depth of field or fog in compositing.
• Normals/World Position: relight accents or isolate directions using advanced compositing.
• Material ID / Object ID or Cryptomatte: fast, anti-aliased selections for per-object/material edits.

Setting up in Rhino

• Rhino Render (Cycles): in Rendering settings, enable available Channels/Passes (e.g., Albedo, Direct/Indirect, AO, Z-Depth, Normal, Emission, Shadow). Save to multi-layer EXR to keep everything in one file.
• V-Ray for Rhino: Asset Editor → Render Elements. Add Beauty, Lighting, GI, Reflection, Refraction, Specular, AO, Z-Depth, Normals, Material ID, Cryptomatte, and Denoiser. Set Cryptomatte to Object or Material IDs based on your workflow. Save as multi-channel EXR.
• Other engines (Octane, Enscape, etc.): enable their pass/AOV system and export EXR; confirm denoiser support per pass.

Compositing workflow tips

• Work in 32‑bit linear EXR; apply view transform (sRGB/ACES) in your compositing app, not baked into the render.
• Layer math that works: add or screen reflections/specular; multiply shadows and AO; color-correct albedo before it combines with light.
• Depth effects: use Z-Depth for DOF and atmospheric haze; clamp and blur the depth pass for smoother bokeh.
• Masking: use Material/Object ID or Cryptomatte to isolate edits cleanly, even on sub-pixel edges.
• Denoising: compare denoised Beauty vs. denoised elements; in V-Ray, the “EffectResult” gives you denoised comp output—keep raw passes for fine control.

Quality and reliability

• Consistent sampling: match noise thresholds so all passes denoise uniformly.
• Avoid clipped highlights: enable highlight clamping or render to EXR with high dynamic range to preserve detail.
• Premultiplied alpha: confirm your app un-premultiplies correctly to avoid dark halos on semi-transparent edges.

File management

• Use multi-layer EXR to consolidate passes; embed color space metadata.
• Name templates: “Project_Version_Camera_Renderer_v###.exr”. Include renderer and camera to avoid mismatches.
• Automate exports via macros or scripts to ensure every shot gets the same pass set.

Pro tip: create a reusable pass preset per renderer and a companion Photoshop/After Effects/Nuke template that auto-wires your comp. Standardization pays off.

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