Tip of the Week - Shuffle, ShuffleCopy, Copy

The following nodes, Shuffle, ShuffleCopy, and Copy are used to reorganize channels into a single branch to ease image manipulation.

You'll notice that Shuffle and ShuffleCopy have an identical panel. The difference is in the DAG.

Shuffle only takes one input, while ShuffleCopy takes two. Copy also takes two inputs. In addition, you can also do a quick full channel change into white or black by just clicking the white or black buttons in the Shuffle Nodes.

Using Shuffle is pretty straightfoward, as it only has one input. You can shuffle channels around into the order you want them to. Let's say you have a mask in a channel called maskA.red, but would like it to be the alpha in your rgba layer. Simply set in1 to maskA and in2 to rgba, and the out1 to the rgb of the rgba layer, and rgb.a to the maskA.red layer.

If you wanted, you could also use maskA.g or maskA.b to pipe into the rgb.a channel. Pretty cool. Here's another Shuffle Node below. What is it doing?

It's setting the outgoing rgb.a channel to completely white, while shuffling in the maskA.r,g, and b channels into the respective maskB.r,g, and b. As you can see, the Shuffle Node is a powerful channel management tool that you can quickly and easily see which channels are getting affected. Let's move on to the Copy Node.

This node has less options than a Shuffle, but it allows you to copy a channel from a different image! A plus of this node over the Shuffle or ShuffleCopy is that it shows you what is being copied within the DAG, allowing for a quick assessment of what you're doing. As you can see from the image on the right, I'm copying my MaskA.red channel from input A into the alpha channel of input B. More often than not you'll see Copy Nodes sprinkled all around a Nuke script. It's set to a default hotkey, K, and it's a quick way to just copy a channel from one input to another. On to the next powerful channel tool, ShuffleCopy!

ShuffleCopy takes the best of both Shuffle and Copy and makes it better. Twice as better? Twice as poweful? That's up for you to decide. While ShuffleCopy only outputs one stream, you can take a combination of different channels from two different inputs and shuffle and copy them around to your hearts content. Instead of in1 and in2 being the same input as in Shuffle, ShuffleCopy maps the in1 to the first input, and in2 to the second input. out1 and out2 are the two different layers in the outgoing stream. What's happening below?

The rgb channels from the first input are becoming the maskA layer of the second input, while the rgb of the second input remains unchanged, while the alpha is being copied from the first inputs alpha. One thing to remember is that these tools are channel replacement tools. They remove the existing channel! If you want to keep the channel, you'll have to use a ChannelMerge node, which is the subject of another future tip!