V-Ray Tip: VRayZDepth-Driven Post DOF: Setup and Best Practices

Use the VRayZDepth render element to drive depth-of-field (DOF) in post for flexible, fast look development and revision-friendly finals.

Set it up correctly in V-Ray

• Add VRayZDepth: Render Elements → Add → VRayZDepth.
• Units and range:
  • Depth black = distance where objects begin to blur least (near limit).
  • Depth white = distance where blur reaches its maximum (far limit).
  • Set these to bracket your whole scene to avoid clamping; push Depth white beyond the farthest object.
• Filtering:
  • Start with Filtering = On for softer transitions and fewer edge halos in most compositors.
  • If your comp tool expects an unfiltered Z (e.g., math-based kernels), set Filtering = Off.
• Bit depth and color management:
  • Save 32-bit float EXR (multichannel if possible). This preserves precision and prevents banding.
  • Work in linear; disable display LUTs on output. Keep “Clamp output” off for EXR saves.
• Camera notes:
  • Disable in-render DOF when planning to do DOF in post to avoid double-blur.
  • Use the VFB focus picker or your DCC’s measure tools to note focus distance for reference in comp.

Compositing workflow (Nuke, After Effects, Fusion)

• Nuke: Use ZDefocus. Pipe the VRayZDepth channel, set math to use true depth, set focal plane to your picked focus distance, and adjust f-stop/defocus amount. Invert the depth channel if the blur direction is wrong (V-Ray is black=near, white=far by default).
• After Effects: Use Camera Lens Blur (or a quality third-party lens blur). Assign the Z-depth pass as the Blur Map, check the layer is linear 32-bit, and invert the map if needed.
• Fusion: Use DepthBlur. Ensure the Depth channel is selected, verify range, and set near/far accordingly.

Quality tips

• Halo control:
  • Pre-multiply your beauty properly and keep depth unpremultiplied where the node expects it.
  • Use edge-extend or matte dilation on foreground elements when halos appear against bright backgrounds.
• Noise:
  • Denoise the beauty before defocus; DOF magnifies noise.
  • Prefer the native V-Ray Denoiser or a high-quality temporal denoiser for animation.
• Banding:
  • Stick to 32-bit float EXR for the Z pass. If forced to 16-bit, add mild dithering to the depth map before blur.
• Transparency and volumes:
  • Standard Z-depth doesn’t look “through” refractive objects as you might expect; consider comp mattes for glass and combine with VRayAtmosphere if volumetrics are present.
• Animation:
  • Keep depth ranges consistent across shots or publish per-shot reference values to avoid “breathing” DOF.

Why this workflow

• Iterate DOF without re-rendering — huge time savings during lookdev and final notes.
• Creative freedom to art-direct bokeh, focus pulls, and rack-focus timing in comp.
• Cleaner pipeline handoffs: one master beauty plus Z-depth and denoised variants.

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