Regrain
Samples the source image’s grain, regenerates and randomizes it for the purpose of adding it to a degrained composite.
1 Add a Regrain node from the Nodes > Filter group.
2 Connect the original plate into the first input, a degrained plate into the second input and then the composite into the third input. The composite should be done over the degrained plate.
Note: A good degrain result is crucial for Regrain to work.
3 Press the Analyze Footage button.
This calculates the response curve of the grain which is then normalized and adapted to the composite.
4 Position the sample box overlay to an area without image detail.
The sample box overlay defines a source area to be used for the grain scattering.
5 Switch between View > Plate Grain and Adapted Grain to see the grain before and after. You may need to adjust the Viewer > Gain and Gamma to see the grain.
6 Set the View back to Regrained Composite and then change the Viewer > Gain back to 0 and the Gamma back to 1 if they were adjusted.
7 If seams appear when scattering the grain, increase Edge Blend to blur the seams or distort them with Distortion Amplitude and Frequency.
Note: Enabling Overlay Cell Pattern displays the cell pattern used to scatter the grain and is useful when setting the Distortion Amplitude and Frequency.
You may want to limit the scattered grain to a matte.
8 Hook up a matte source to the optional Matte input.
9 Activate the Replace > Matte > Enable checkbox.
10 In the Channel pop-up menu, select the desired matte channel.
The scattered grain is now limited to the matte with the original plate grain outside of the matte.
11 To composite the new grain outside of the Regrain node, add a Grain Composite node and connect the degrained composite to the first input and the Regrain > Grain Only output to the second input.