Nuke Tutorial: How to extract alpha’s from CosmicVFX

Here is the step by step tutorial on how to extract the alpha’s using Nuke by The Foundry.

NOTE! This is not the only way of extracting alpha’s and not all elements in our library are set up to extract it this way but this setup covers about 90% of the extraction process for our VFX Stock Footage.

This setup is just our recommendations as we created ideal lighting and sets to film each element. By using this process we stay as true as possible to every pixel for your composite.

Step 1

Make sure to denoise the element first.

We do that by pressing Tab - then write “denoise” - press enter to create the node. Make sure to put a framehold node in the Noise pipe.

Step 2

Then create another framehold and hold the frame where there is nothing to see in the footage. (most cases would be the first or the last frame).

Step 3

Now we want to extract the difference between the framhold and all the other frames by using the Difference keyer. We will then pipe A and B like shown above. By doing this we get all pixels that moves extracted as an alpha as we compare them to the framehold.

Press Tab - Write “difference” - press enter to create the node.

Step 4

Now we create a Grade node, (shortcut: “G” on your keyboard). Make sure you only manipulate the alpha channel.

Then adjust the intensity of the alpha by the multiply, white point value. And adjust the black point to around 0.002 to remove the noise that we extract from the difference keyer.

(play around with the values for each element to finesse the pixels for the alpha channel).

The Foundry: Nuke Software Hollywood quality compositing tool. A grade node that shows the details values for black and white points

Step 5

Now you can use the elements as you see fit. We recommend to export it to optimize performance in Nuke as all elements are in 4K. To do that you can press tab and write “write”. Create the node and set the path where you want to export and choose a format that suits your pipeline.

Have fun creating!

As shown in the picture. This is the whole setup you need in order to extract our elements in the best possible way and obtaining as many of the original pixels as possible.

This setup is also fast for Nuke to process.