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Creating supplemental keys

From: Nuke 6 New Features

Video: Creating supplemental keys

Comparing the preliminary composite to the original green screen has revealed the loss of detail in the feathers, so now we have to create a supplemental key that's optimized for the feathers. So let's scoot in here to our green screen. And to do that, I'm going to use the Primatte node, so come up to the Keyer tab, Shift+Click on Primatte. And I'll hook my viewer up by typing 1 on the keyboard. And we'll start by selecting the background color like so. We'll switch to the alpha channel.

Creating supplemental keys

Comparing the preliminary composite to the original green screen has revealed the loss of detail in the feathers, so now we have to create a supplemental key that's optimized for the feathers. So let's scoot in here to our green screen. And to do that, I'm going to use the Primatte node, so come up to the Keyer tab, Shift+Click on Primatte. And I'll hook my viewer up by typing 1 on the keyboard. And we'll start by selecting the background color like so. We'll switch to the alpha channel.

The beautiful part about this is I'm going to be able to dial in the Primatte keyer for the best possible look for the feathers and I can ignore everything else in the picture. So let's go on to clean the background noise. In fact, I am going to push up the viewer gamma so I can see any contamination in the backing region. So I just want it to be nice right here. I don't care about any of the stuff over there, no problem. So we'll clean the foreground noise, and for that I'll push the viewer gamma the other way, so I can see holes in my core matte, and I'll select this.

All right, and again--I'll re-home the viewer-- I don't care that the shirt is messed up. I don't care whether there is stuff in the corner, because I'm only concerned about the best possible matte with the feathers. All right, so let's zoom back in to the feathers. I want to beef up those dark feathers here. We can them a little bit if we pull up the viewer gamma, so for that I'm going to use the Matte tool and beef up that part of matte there, this part over here, maybe a little there, and set my viewer gamma back to normal, and maybe a little bit up here.

Okay, so let's say we like that. The next step is I have to isolate this part of this key and merge it with the main master key. To do that, I'm going to attach a Roto node to the Primatte, just by typing O on the keyboard. I'll zoom out a little bit and I'll draw myself a little shape to isolate the area I'm interested in. Then of course I'm going to invert the shape and then color it black.

So now I've exactly the part of the picture I'm interested in. I don't care about any other part of this picture. So now the last step is to merge this with the main master key. Okay, let's clear the Property bin and re-home the viewer and take a look down here. So my purpose is I want to take this master key and combine it with that hair key such that I get the best of both. To do that, another ChannelMerge node. I'll hook up one side here, pull it out a little bit, hook up the other side to my little hair detail, and then we'll hook the viewer up over to that and switch to the number one input of the viewer so we can see what we're doing.

Now if I toggle the ChannelMerge node on and off, you see what's happening. I'm losing the master key. What I really want to see is the difference that my extra key has made. So to do that I'm going to swap the inputs with a Shift+X. So I'll select the node and type Shift+X on the keyboard and now the inputs has been swapped. Now watch what happens. When I disable the node on and off with the D key, I'm seeing now the addition of my new and improved feather key.

Now that we've merged the supplemental key with the master key, let's take a look at the merge operation that we're using for this. The operation in the ChannelMerge node, by default, is union. However, we have several choices. I might say plus. Well, when I said plus, it kind of chocked up the core matte there. We'll go back and compare it to union: the union and plus. Another option would be max, so let's take a look at the max.

So this is giving me the maximum between the pixels of the supplemental key and the master key, and that actually looks a lot nicer. We'll compare max to union and union to plus and plus to max. So let's say max is the best look and that's the one I want to use. Now I need to use this version of the matte for my composite, so I'll just move the alpha channel from this Copy node to here, switch my viewer over to the AddMix node, switch to the RGB channel so I can see my composite, and now I can toggle this node on and off to see the improvement that I've made. There, much more hair detail.

Now that we have everything hooked up and working, we could introduce some additional processing if we wanted to on the hair matte, like blurs and dilates and anything like that, to refine just the feathers for optimal look. Okay, we're ready to do our color correction now, so let's pull down here, get the ColorCorrect node opened up, home the viewer so we can see the whole thing. Keep in mind that the ColorCorrect node is on the unpremultiplied image, so we would not set the ColorCorrect node here for unpremultiply; that would be wrong.

So we'll go back to our ColorCorrect node, we'll reconnect to our composite so we can watch our color correction in context. I don't want to spent a lot of time color correcting, so I'm just going to tap up the gamma a bit and then inch up the gain so our boy kind of pops out of the picture. Now that we've assembled the master key by combining several different keys from different keyers, we can explore some alternate workflows beyond just the AddMix node.

Show transcript

This video is part of

Image for Nuke 6 New Features
Nuke 6 New Features

59 video lessons · 5804 viewers

Steve Wright
Author

 
Expand all | Collapse all
  1. 7m 45s
    1. Welcome
      1m 56s
    2. What is NukeX?
      5m 0s
    3. Using the exercise files
      49s
  2. 1h 11m
    1. Learning the interface
      5m 15s
    2. Drawing shapes
      1m 41s
    3. Editing shapes
      5m 1s
    4. Keyframe animation
      6m 4s
    5. Property panel tabs
      7m 8s
    6. The shape list
      4m 26s
    7. Output settings
      1m 11s
    8. Workflow examples
      5m 33s
    9. Creating garbage mattes
      4m 55s
    10. Drawing strokes
      4m 16s
    11. Editing strokes
      4m 30s
    12. The Clone tool
      1m 37s
    13. Editing the Clone tool
      2m 54s
    14. The Reveal tool
      9m 2s
    15. The Blur tool
      2m 21s
    16. The output mask
      2m 57s
    17. The Dodge tool
      2m 32s
  3. 27m 38s
    1. Basic compositing
      3m 51s
    2. Using the Screen controls
      2m 50s
    3. Using the Screen Matte controls
      3m 37s
    4. The Crop feature
      2m 28s
    5. Holdout and garbage mattes
      2m 19s
    6. The Tuning controls
      1m 58s
    7. The Bias controls
      2m 37s
    8. Screen replacement
      2m 15s
    9. Multipass keying
      4m 37s
    10. Color-correcting the foreground
      1m 6s
  4. 17m 8s
    1. Basic setup
      3m 24s
    2. The Ultimatte workflow
      5m 18s
    3. Using the matte tools
      4m 16s
    4. Spill suppression
      4m 10s
  5. 28m 8s
    1. Overview
      2m 42s
    2. Pre-processing the greenscreen
      3m 25s
    3. Creating specialized keys
      7m 14s
    4. The preliminary composite
      6m 14s
    5. Creating supplemental keys
      6m 22s
    6. Alternative workflows
      2m 11s
  6. 24m 39s
    1. Editing control points
      4m 49s
    2. Editing the warp grid
      2m 52s
    3. Keyframe animation
      4m 42s
    4. Morphing
      10m 7s
    5. Additional tabs
      2m 9s
  7. 33m 20s
    1. Drawing splines
      6m 3s
    2. Drawing open splines
      2m 0s
    3. Limiting the warp
      7m 1s
    4. Warping to a target image
      5m 54s
    5. Morphing
      8m 1s
    6. The correspondence points
      4m 21s
  8. 9m 3s
    1. The MotionBlur2D node
      5m 55s
    2. Using the VectorBlur node
      3m 8s
  9. 10m 29s
    1. The ZBlur node
      6m 33s
    2. Image-based blurs
      3m 56s
  10. 11m 13s
    1. Navigating the Dope Sheet
      5m 17s
    2. Shifting keyframes
      5m 56s
  11. 5m 22s
    1. Making a group
      2m 50s
    2. Making a gizmo
      2m 32s

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