Month: February 2024

Week 14 – Adjusting Multipass and Relighting

Importing 3D Files and Texture Replacement:

• Utilize the ReadGeo node to import 3D model files in formats such as fbx or abc.
• Replace textures in Nuke using the STMap node. Create an STMap using UV expressions, connecting the source and the STMap to dynamically alter the texture based on the STMap.

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Workflow for Adjusting Multipass Images:

• When working with multipass images, it’s crucial to unpremult all channels (set knob ‘divide’ to ‘all’, default: RGB).
• Subtract the AOV you want to adjust using the Merge node with the ‘from(B-A)’ operation.
• Perform color grading on the pass and merge it again.
• Remove all channels except RGBA using the Remove node to avoid unnecessary calculations.
• Finally, premultiply it again.

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Relighting

Position Pass:

• Represents the 3D scene in color values (Red: x-coordinate, Green: y-coordinate, Blue: z-coordinate).
• Utilize the PositionToPoints node to visualize it in 3D space.
• Depth channel stores the distance from a point in 3D to the camera’s position.

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Relighting Setup v01/02:

• Use the PositionToPoints node to generate a 3D preview of the geometry in the rendered image.
• Connect incoming diffuse, normals, and camera data into the ReLight node.
• Add a material to control how the geometry reacts to new lighting.
• Add lights grouped into a Scene node visible to both the 3D preview and the final image.
• Merge the result over the existing plate.

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Relighting Setup v03:

• Similar to the normal process, unpremult all passes, and apply the PP_Mask_hub Gizmo with the Position pass.
• Create alpha from a picked color on the viewer, set the alpha, connect to Grade node for its mask, and then premultiply all passes again.

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Relighting Setup v04:

• Follows the same overall process as v03 but uses the W_SuperNormal Gizmo with the Normal pass.
• Pick a color on the viewer, move the position of light horizontally and vertically.

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Tips:

• Relative Path:
  • Use relative paths in Project settings to target directories easily. Find it in Project settings -> Root -> Project directory -> Script Directory.
  • Copy and paste the directory before your folder directory, typically ‘[python {nuke.script_directory()}]/’.
  • Essential for collaborative work or moving to different computers to streamline relinking.
• Create Custom Node:
  • Share your custom nodes easily by copying and pasting from Nuke to Notepad (create) or copying text and pasting in Nuke (apply).