V-Ray Tip: V-Ray Velocity Pass Workflow for Accurate Compositing Motion Blur

Use the Velocity render element to add high-quality motion blur in compositing while keeping renders fast and flexible.

Set up the Velocity pass in V-Ray

• Add the Velocity (Motion Vector) render element to your scene. Name it clearly if you output many AOVs.
• Work in float: save multi-channel EXR (16-bit half or 32-bit) to preserve negative values and large magnitudes.
• Set a sensible Max Velocity so vectors normalize without clipping. Start by scrubbing a fast-moving frame and set Max Velocity just above the largest observed motion; increase if you see “frozen” fast objects in comp.
• Match shutter to editorial: for 24 fps and a 180° shutter, use a shutter duration of ~0.5 frame. Inconsistent shutter settings between 3D and comp cause over/under blur.
• For deforming meshes, enable deformation blur in render settings (low geometry samples are often enough) so the Velocity pass captures vertex motion as well as transforms.
• Consider disabling image filtering on the Velocity element to avoid edge mixing; use coverage/mattes to refine edges in comp.
• Keep in-render motion blur off for beauty during lookdev and many finals—Velocity in comp is faster to iterate and easier to tweak shot-by-shot.

Use the pass in compositing

• Import the EXR and point your Vector/VectorBlur node to the Velocity channels (R = X, G = Y). Many tools expect screen-space vectors in pixels-per-frame.
• If blur goes the wrong way vertically, invert the Y channel; if horizontally wrong, invert X. Different apps use different conventions.
• Adjust scale/gain to match on-set shutter feel; start at 1.0 and compare to a quick in-render MB test frame for parity.
• Increase vector samples in the node for fast movers to avoid stepping; keep as low as possible for speed on sequences.
• Use Cryptomatte and Object/Material ID AOVs to isolate elements that need different blur intensities (e.g., hero props vs. background).
• Combine with Z-Depth to mask blur in out-of-focus areas when mimicking camera behavior.

Calibration and quality checks

• Test on a frame with maximum screen-space motion; check edges for clipping or fringing. Raise Max Velocity or output 32-bit if needed.
• For retimed footage, rescale vectors by the retime factor to keep blur physically plausible.
• Beware limitations: 2D vector blur can’t reproduce occlusion changes or complex parallax from large depth differences—render true 3D motion blur for hero shots where needed.
• Keep frame rate consistent across CG and editorial. Per-frame vectors assume the timeline’s base FPS.

Pipeline tips

• Bundle Velocity, Z, Cryptomatte, Light Select, and Denoiser AOVs in a single multi-channel EXR for robust downstream control.
• Document shutter and Max Velocity in the shot metadata so comp can match settings without guesswork.
• Use the V-Ray Frame Buffer A/B comparison to line up a quick in-render MB test against the vector-blurred comp result.

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