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Month: November 2023

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Week 8 – Clean Up in Nuke
Roto Paint

The RotoPaint node offers a more extensive set of tools compared to Roto, although many controls are shared. It is employed for cleaning up and cloning out undesired elements from the plate (heavier than the Roto node) (Shortcut: P).

Brush settings
  • Clone: Ctrl+set the area-paint (Shift: adjust brush size).
  • Reveal: Reveals the original background when painted (ensure ‘paint source’ is set to ‘bg’).
  • Paint: Enables drawing on the shot.
  • Blur, sharpen, smear, dodge, burn: Adjusts the area painted on the shot (similar to Photoshop).

Components you can adjust:

  • Clone: Change the area set for cloning (translate, rotate, scale, etc.).
  • Stroke: Adjust opacity, size, and hardness of the brush (you can change brush settings in the Stroke tab even after brushing).
  • Lifetime: Single – show one frame, all – every frame. Check the right side of the roto name (or the Lifetime tab). When checking the roto node on the viewer, make sure to check its lifetime. For example, if you worked or set the lifetime on a single frame to 500, you cannot check it on frame 520.

After finishing the roto brush, be sure to change ‘output mask’ to ‘rgba.alpha’ to premultiply your roto work (to change this knob, click the little triangle between ‘clip to’ and ‘color’).

For checking separated and merged versions, you can use this node structure.

Denoise and Grain
  • Grain originates from the film’s structure, where random patterns on moving images are the shapes of the crystals.
  • Digital noise arises from the sensitivity of the sensor and how the image is subsampled.

Grain and noise share a similar look, feel, and texture on the filmic image. Tools used for both digital and film source footage include grain, perspective, and denoise, contributing to a more organic scene.

Clean up process

When replacing something on a grainy video, a common process involves denoising it, tracking, and then reintroducing grain because the grain changes frame by frame(In studios, the ‘Neat Video’ plugin is often used for denoising.)

  • Denoise node: Connect it to a source, set the bounding box to analyze its noise, and adjust Denoise amount, Smoothness, etc.
  • Grain node: It is Challenging to match the grain to the original. Match each channel by adjusting size, irregularity, intensity.
  • F_ReGrain node: More accurate than Grain node, connect grain to the original shot and connect Src from the shot you want to match (Only in NukeX, heavy).

You can easily insert images using Cornerpin following this process:
Track cornerpin – export CornerPin data – invert area (unwrap) – crop – add something – cornerpin back (wrap). Make sure to insert a ‘crop’ node; if you don’t crop it, the bounding box will be extremely large.

02.12.2023 added

Utilizing the Color Space node, set the output to ‘Cineon’ for optimal detail in dark areas.

Change the color space of both the original plate and denoised plate to ‘Cineon’ and merge them using the ‘minus’ operation. After cleaning up with the denoised plate, also convert the color space to ‘Cineon’. Finally, merge both nodes with the ‘Plus’ node and convert the color space back to the original. While this method may be considered old-fashioned, it works well, especially in flat areas.

DasGrain Gizmo: This industry-standard tool is compatible with any version of Nuke. Utilize three inputs (denoised plate, cleaned-up comp, original plate) and click ‘Analyze’. Using the CommonKey Gizmo, set the alpha area and premultiply the regrained comp. Merge it over the original input. DasGrain is an easy-to-use yet powerful tool for matching grain effectively.