Realistic Rain Drop VFX in DaVinci Resolve

Tech/Workflow Summary: Realistic Rain Drop VFX in DaVinci Resolve (Fusion)

Goal / Approach

Create a dynamic, realistic raindrop effect in Fusion using:

• A particle system (P emitter + P render) for falling drops/streaks
• Procedural textures (Fast Noise + expressions) for static raindrops on glass
• Bump/displacement + lens blur to convert a 2D rain texture into believable depth and optical softness

Emphasize correct color pipeline handling: Fusion nodes should operate in linear color, while the viewer can preview in Rec.709.

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1) Color Management (Linear workflow inside Fusion)

1. Convert the clip to a Fusion clip.
2. Add Shift/Space → Gamut to convert the source into linear (e.g., Rec.709 scene → linear).
3. For correct preview, use the Viewer’s Gamut view L:
   • Set output/view space to Rec.709 scene to match expected appearance.
   • Avoid applying the Rec.709 transform twice, or the result will look incorrect (too bright/dark).
4. Save these settings using Save Default so you don’t repeat the setup.

Key concept: Nodes work in linear, but the viewer can display in Rec.709 for sanity and consistent lighting/reflection accuracy.

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2) Raindrop Texture Design (particle map base)

• Start with a Background node:
  • Set Color = white
  • Disable Auto resolution
  • Scale down to create a thin, streak-oriented texture
• Use masks:
  • An Ellipse mask feeding into Background (often full coverage, then softened)
  • A Raise node for the trail/streak:
    • Configure center (0.5) and Y (e.g., -50) to create a straight upward ray/streak
    • Tweak decay/weight/exposure to control length and brightness
  • Add a rectangle mask to control streak width and soften edges

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3) Particle System Setup (P emitter + P render)

Core nodes

• Create a P emitter and connect to a P render node.
• Set P render output to 2D.
• In P emitter → Style:
  • Set Style = bitmap
  • Plug the Raise output into the bitmap/texture slot so each particle uses the raindrop streak.

Appearance/performance controls

• Set particle size (e.g., size = 1).
• Add Shift/Space → Scale after to scale by resolution (e.g., slider around 0.5) to avoid high-res particle costs.
• Add size variance for natural variation.

Spawn/fall behavior

• Conditions → number: about 3 particles per frame (kept low for control)
• Region: a rectangle spawn line
  • width ~1, height ~0
  • extend beyond frame (e.g., ~1.3)
• Controls → velocity: gravity-like fall
  • angle = 90
  • tweak velocity as needed
• Add velocity variance so drops don’t all move identically.

Prevent drops from disappearing too early

• Increase lifetime from ~100 to ~160 frames.

Ensure particles exist immediately

• Enable pregenerate frames (e.g., 50–80) so the particle field is populated during playback.

Overall realism scale adjustment

• Reduce emitter size for realism (e.g., set particle scale to 0.15 instead of 3, when desired).

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4) Static Raindrops on the Window (Fast Noise based mask)

• Duplicate/paste and add more “stuck to glass” droplets using:
  • Fast Noise (tune scale, contrast, brightness)
• Avoid overly flat “all white” regions by adjusting contrast/brightness and adding texture detail.
• Add subtle motion:
  • Use Expression on Y position: subtract time, divide by 5000 (very subtle gravity-like drift)
• Prevent negative/invalid values:
  • Add Brightness/Contrast with alpha enabled and clip black values
  • This prevents artifacts from values below 0 (e.g., negative edge coordinates)

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5) Animate & Distort Rain Paths (Displace + displacement texture)

• Combine rain layers into a merged particle map (merge).
• Add Shift/Space → Displace:
  • Drive displacement with another Fast Noise
  • Set displacement to X and Y
  • Adjust X refraction (around 0.5)
  • Keep X offset = 0 to reduce drifting
• Refine displacement noise amount/scale to bend naturally without extreme stretching/splitting.

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6) Turn Texture into 3D-ish Depth (Bump Map + Displace)

1. Convert displacement output to a Bump Map:
   • Use Create Bump Map node
   • Set height scale (e.g., ~4) for visibility
2. Apply via Displace:
   • Plug bump map into the foreground input of Displace
   • Type = X and Y
   • Use offsets (e.g., X offset ~0.5, Y similar)
   • Use stronger offsets for impact (e.g., X/Y refraction around ±1.5, depending on direction)

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7) Optical Realism: Lens Blur, Lighting, Smoothing

Lens blur

• Add lens blur for realistic optical softness:
  • Prefer Lens Blur (Studio-only) for performance
  • If using a free alternative: Defocus
• Add Brightness/Contrast before lens blur to control background brightness/gain.

Shadow/interaction from bump/displace

• Use light shading settings:
  • Set light channel to Luma (black/white only) rather than color channels
  • Adjust light power and angle subtly

Cleanup harsh edges

• Increase spread to smooth edges.
• Optionally add slight blur after bump/displace to reduce jaggedness (don’t overdo, or it gets muddy).

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8) Raindrops-Only Pass / Masking Output

• Create a raindrops-only version by using the displacement texture as a mask:
  • Plug it into the displace mask input
  • Multiply by mask so the background disappears where the mask is black
  • Tune low/high thresholds so droplets remain visible

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9) Fun customization: text-reactive rain

• Workflow concept: add text before lens blur
• The rain effect updates to reflect the text, implying the rain displacement/lens blur is applied after text compositing.
• Add glow and color corrector for neon/graphic styles.

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Speaker / Source (from subtitles)

• Primary speaker: the tutorial creator (subtitles reference their “Editor collection / Editor titles packs” and “Fusion Friday series”; name not explicitly stated)
• Video source: YouTube video titled “Realistic Rain Drop VFX in DaVinci Resolve”