C_ColourMatcher

C_ColourMatcher aims to produce a global gain-based color correction across all the views in a rig to balance out differences in exposure and white balance. It solves across all cameras to find the minimum required gain changes to ensure color similarity.

Note: C_ColourMatcher does not compensate for color shifts not resulting from exposure- or gain-type differences. It also does not deal with gamma- or offset-type differences.

Color matching relies on solve data and should be performed before stitching the solved camera output together, so ideally, place C_ColourMatcher between C_CameraSolver and C_Stitcher.

Inputs and Controls

Connection Type	Connection Name	Function
Input	Source	A preview sequence from C_CameraSolver to color correct.

Control (UI)	Knob (Scripting)	Default Value	Function
C_ColourMatcher Tab
Local GPU	gpuName	N/A	Displays the GPU used for rendering when Use GPU if available is enabled. Local GPU displays Not available when: • Use CPU is selected as the GPU device in the Preferences. • no suitable GPU was found on your system. • it was not possible to create a context for processing on the selected GPU, such as when there is not enough free memory available on the GPU. You can select a different GPU device, if available, by navigating to the Preferences and selecting an alternative from the GPU Device dropdown. Note: Selecting a different GPU requires you to restart Nuke before the change takes effect.
Use GPU if available	useGPUIfAvailable	enabled	When enabled, rendering occurs on the Local GPU specified, if available, rather than the CPU. Note: Enabling this option with no local GPU allows the script to run on the GPU whenever the script is opened on a machine that does have a GPU available. You should also select this if you wish to render from the command line with the --gpu option. See Nuke 15 Release Notes for more information on the GPUs Nuke supports.
Input
Projection	inputProjectionType	Default (source)	Sets the input projection type: • Default (source) - the source input is connected to a C_CameraSolver and uses the images and metadata to color correct the output. • Latlong - the source input is connected to a panorama that has already been converted to latlong space.
Keying
Match Keys	Key number	1	Displays the total number of stitch keyframes added to the sequence.
Match Keys	Key count	1	Displays the current stitch keyframe.
	N/A	N/A	Click to jump to the previous keyframe.
	N/A	N/A	Click to jump to the nextkeyframe.
	N/A	N/A	Click to add a keyframe at the current frame in the sequence.
	N/A	N/A	Click to delete the keyframe at the current frame in the sequence.
Step	keyStep	500	Sets the interval between keyframes for the Key All button.
Key All	addAllAnalysisKeys	N/A	Click to add keyframes to the sequence at intervals set by the Step control.
Delete All	deleteAllAnalysisKeys	N/A	Click to delete all keyframes from the sequence.
Import	importAllKeys	N/A	Click to import existing keyframes automatically from C_CameraSolver, C_ColourMatcher, or C_Stitcher nodes in the current script. Note: Importing keyframes deletes any existing keyframes.
Analysis
Match	matchType	Exposure	Sets the type of match to calculate: • Exposure - calculates exposure differences and corrects across all cameras. • Exposure and Colour - calculates exposure and color differences and corrects across all cameras.
Analyse	solveGainCompensation	N/A	Click to analyze the selected match type across all cameras.
Reset	deleteGainCompensation	N/A	Click to delete the calculated analysis.
Output
Gains	gainsOutput	1	Displays the gains per view once the analysis pass is complete.
Exposure	globalExposure	0	Adjusts the global exposure across all cameras.
Format	outputFormat	dependent on Compositing environment Project Settings	Sets the output resolution passed down the node tree. Typically, you would set the format globally in the Project Settings, but this control overrides the global setting.
Converge	convergenceDepth	10	Sets the depth at which the cameras overlap, allowing you to bring particular areas in the scene into focus to check color matches.
Export
Export menu	exportMenu	STMaps (split)	Sets the export nodes to add to the Node Graph: • Grades (split) - creates a single Grade and Exposure node containing the calculated exposure and color differences. • Grades (separate) - creates separate Grade and Exposure nodes for each view containing the calculated exposure and color differences. • OCIO CDL Transforms (split) - creates a single OCIOCDLTransform and Exposure node containing the calculated exposure and color differences. • OCIO CDL Transforms (separate) - creates separate OCIOCDLTransform and Exposure nodes for each view containing the calculated exposure and color differences.
Create	exportButton	N/A	Click to create the export specified in the export dropdown.
Python Tab (These controls are for Python callbacks and can be used to have Python functions automatically called when various events happen in Nuke.)
before render	beforeRender	none	These functions run prior to starting rendering in execute(). If they throw an exception, the render aborts.
before each frame	beforeFrameRender	none	These functions run prior to starting rendering of each individual frame. If they throw an exception, the render aborts.
after each frame	afterFrameRender	none	These functions run after each frame is finished rendering. They are not called if the render aborts. If they throw an exception, the render aborts.
after render	afterRender	none	These functions run after rendering of all frames is finished. If they throw an error, the render aborts.
render progress	renderProgress	none	These functions run during rendering to determine progress or failure.