Nuke OCIOCDLTransform Format Support¶

cdl_convert supports full bidirectional conversion with OCIOCDLTransform nodes saved in The Foundry Nuke’s nuke scripts (.nk files). This allows for seamless integration with Nuke-based VFX and compositing workflows. Only tested with a single OCIOCDLTransform node per script.

OCIOCDLTransform Node Format¶

Nuke’s OCIOCDLTransform node format is a simple text-based format that stores ASC CDL color correction values:

OCIOCDLTransform {
  slope {1.2 1.0 0.8}
  offset {0.1 0.0 -0.1}
  power {1.0 1.1 0.9}
  saturation 1.2
  name shot_001_grade
}

Format Structure¶

slope: Three space-separated float values for RGB slope
offset: Three space-separated float values for RGB offset
power: Three space-separated float values for RGB power
saturation: Single float value for saturation
name: Node name (used as ColorCorrection ID)

Command-Line Usage¶

Converting from Nuke Format¶

Convert a Nuke OCIOCDLTransform node to other CDL formats:

# Convert to Color Correction Collection
$ cdl_convert shot_001.nk -o ccc

# Convert to multiple formats
$ cdl_convert shot_001.nk -o cc,ccc,cdl

# Specify output directory
$ cdl_convert shot_001.nk -d ./output/ -o ccc

Converting to Nuke Format¶

Convert other CDL formats to Nuke OCIOCDLTransform nodes:

# Convert from CCC to Nuke
$ cdl_convert input.ccc -o nk

# Convert from ALE to Nuke
$ cdl_convert input.ale -o nk

# Convert with validation
$ cdl_convert input.cc --check -o nk

Python API Usage¶

Parsing Nuke Files¶

import cdl_convert as cdl

# Parse a Nuke OCIOCDLTransform file
cc = cdl.parse_nk('shot_001.nk')

# Access CDL values
print(f"Slope: {cc.slope}")
print(f"Offset: {cc.offset}")
print(f"Power: {cc.power}")
print(f"Saturation: {cc.sat}")
print(f"Node name: {cc.id}")

Writing Nuke Files¶

import cdl_convert as cdl
from pathlib import Path

# Create or load a ColorCorrection
cc = cdl.ColorCorrection('shot_001_grade')
cc.slope = [1.2, 1.0, 0.8]
cc.offset = [0.1, 0.0, -0.1]
cc.power = [1.0, 1.1, 0.9]
cc.sat = 1.2

# Set output path and write
cc.file_out = Path('output.nk')
cdl.write_nk(cc)

Converting Between Formats¶

import cdl_convert as cdl
from pathlib import Path

# Parse from one format
cc = cdl.parse_cc('input.cc')

# Write to Nuke format
cc.file_out = Path('output.nk')
cdl.write_nk(cc)

# Or use parse_file for automatic format detection
cc = cdl.parse_file('input.ccc')
cc.file_out = Path('output.nk')
cdl.write_nk(cc)

Format Characteristics¶

Single Node Per File¶

The current implementation supports one OCIOCDLTransform node per .nk file:

When parsing, only the first OCIOCDLTransform node is extracted
When writing, a single node is generated
For multiple corrections, write separate .nk files

Workflow Examples¶

VFX Pipeline Integration¶

import cdl_convert as cdl
from pathlib import Path

# Parse CDLs from DI department (CCC format)
collection = cdl.parse_ccc('di_grades.ccc')

# Export each correction as a Nuke node for compositors
output_dir = Path('./nuke_grades/')
output_dir.mkdir(exist_ok=True)

for correction in collection.color_corrections:
    correction.file_out = output_dir / f"{correction.id}.nk"
    cdl.write_nk(correction)
    print(f"Exported {correction.id}.nk")

Batch Conversion¶

# Convert all Nuke CDL files in a directory to CCC
for file in *.nk; do
    cdl_convert "$file" -o ccc -d ./converted/
done

Error Handling¶

Missing Required Fields¶

When parsing Nuke files, if required fields are missing and halt_on_error is False (default), the parser will:

Return None for missing fields
Use unity defaults where appropriate
Continue parsing without raising exceptions

With strict validation:

$ cdl_convert --halt input.nk -o ccc