Category: Nuke tips

BlacksMatch

June 30, 2019

For those who just want to quickly see what the tool does, I’ll include a time-stamped link to that part of the Demo here:
https://youtu.be/Kw3bcsmkGuk?t=2145

BlacksMatch recreates a Toe operation with merge nodes, meaning you can now plug in an external image are your black color and it will perform the operation taking each pixel’s value into account as the blackpoint.  

You can control the Multiply, which is how far above the blackpoint the blacks match with stop affecting your midtones and highlights.  For example, if you plugged in 0.15 and had the multiply set to 2, then values above 0.3 remain unaffected.  

The “falloff” or Gamma control just controls the falloff of the curve into your blackpoint color.  if it’s really high, it will act more like a screen or plus (still ending at the blackpoint color times your multiply control), and if it’s really low, it will act more like a clamp.  Your blackpoint will not ever fall below your input color while you manipulate the curves.

There is a preview plotscan button that helps you visualize how your curve is behaving with your settings.  Just move the plotscan picker around and it will sample your blackpoint color at that area and give you an overlay of your curve.  (Don’t forget to turn it off when you are done)

I personally think this is a tool every comper should have in their toolkit, as it’s by far the most controlable way to match your blacks properly!

The settings of the BlackMatch Tool and a wipe from the tutorial:

BlacksMatchTutorial_ThumbforNukepedia.jpg

There is a full video Tutorial about the BlacksMatch workflow, along with a Tool Demonstration at the end.  If you want to know how I made it and whats going on under the hood, please watch the whole video. It might give you some ideas of how to re-think your matching blacks workflow.

Here is the Flow Chart for the Blacks Match Workflow:

Our goals are:

1.) Nothing should fall below the blackpoint value

2.) The blackpoint should affect the mids/highs as little as possible.

The Most important thing to remember is to try and not adjust any color corrections after you apply your blackpoint.

Here’s a few examples of the importance matching blacks can be to your image:

Here is a picture with just some beauty rendered statues, color corrected and placed into our scene, no blacks match… stands out quite a bit:

Here is a before picture is we just turn off all the color and detail and just place “pure black” statues into our scene:

If we start sampling the colors around the surrounding areas of the statues and applying theses as our blackpoint, still ignore any midtone/highlight color or detail. We can actually see our statues are fitting in quite nicely. You can think of it like “if there were pure black objects in my scene in that area, what would it look like?” and we are getting pretty decent results:

And here is the image with our matched blacks properly combined with our midtones and highlights. But there is a lot of operations used to combine the blackpoint with the midtones and highlights. So let’s take a look at all of them, and study the best way of combining these:

For the second part of our goal, the blacks should affect our midtones and highlights as little as possible. We have to look at different operations of how to apply our blackpoint:

Here’s some graphs comparing the most common operations of how to match the blackpoint and what they are doing to a 0-1 curve.

Here’s a closer look at the curves next to each other:

Here is just an overlay of all the curves on top of each other to compare them to one another:

Here is a close up of a Clamp operation:

Here’s a close up of the plus operation:

Here’s an example of a Screen operation:

A close up of a Hypot operation:

A close up of a Toe operation:

Let’s now talk about the Good, the Bad, and the Ugly… starting with the bad:

A screen and lift do a sililar operation between 0-1, but the screens influence stops at 1, where as a lift is actually using 1 as a pivot point to lift the blacks and lower the highlights above 1. If you set a lift to 1, it will completely decontrast the image, sandwiching every pixel and turning the entire frame to 1.

No matter if you leave a color correct at default range, or start adjusting the range curves, the color correct produces some very strange results because of the S-curve it generates. Because it is sampling the luminance from the bg image, if you enter a black point number higher than the luma key it is calculating, than the curve will first be your black point color, then dip back down to the midtone color and rise back up to your highlights. This creates a really strange image that you’ll want to avoid.

Avoid Lift on a Grade, and avoid ColorCorrect nodes for adjusting your blackpoint.

The Ugly:

Both Clamp and Plus are at the Extremes of our operations, and have the least appealing qualities. You can acheive much more control and better operations using our remains screen, hypot, and toe operations. Here is the gif of the curves compared to one another again so you can see that clamp and plus are at the extremes:

Screen and Hypot are perfectly fine operations, but offer limited control. and Toe… Well we can’t even input an image, and we don’t even know what exactly it is doing. There’s very little documentation on it. Let’s try to reconstruct it:

With a little bit of fiddling around. We can see the top of the toe operation is exactly double the value of the blackpoint… We need to start by re-creating a screen, which is basically an inverted luminance key, used as a mask, that is plusing out blackpoint. From there we can create a screen operation that instead of end at 0-1, ends at 0 to 2x the balckpoint value, and you can see in the example above we have a mini triangle encompassing our toe operation. There it’s a matter of using a gamma of 0.5 on the luma-key mask and we have our toe.

So to reiterate:

A toe is an inverted luma-key, that instead of 0-1 is 0-‘2x the blackpoint color’ and then is gammed by 0.5 and is used as a mask to plus the blackpoint color over the image.

I know… that’s a mouthfull. But what we take away from making this toe for ourselves is that we have controls over 2 things. The multiply of how far above the black color it is affecting our midtones and highlights. And the gamma curve that is controlling our falloff of the curve towards the blackpoint value.

With this knowledge and math, we can create a tool that uses merges to do our math operations, which mean me can plug in an external image as out blackpoint and expose controls for the mult (above the blackpoint) and gamma (falloff) of the curve. And now we have our BlacksMatch tool.

Download the tool from Nukepedia here:

http://www.nukepedia.com/gizmos/colour/blacksmatch_20

Or download the tool from my github, where you can find a repository with all my tools in one place:

https://github.com/CreativeLyons/Lyons_Tools_Public/blob/master/05_Color/BlacksMatch.nk

I’ve received a few requests for the script and images I’ve used in the tutorial, so I’ve put together a folder on my dropbox for you guys to download and play around with.
This is a preview of the part of the script I am saving for you. It includes the statues over the temple example, a couple of the simple shapes over complex black level images, and the part of the script that I recreated the toe, with the animating graph.

I’m also adding a reference image folder, with some of the cool hazy/foggy complex black point images I found while researching this topic. Maybe they will be good practice for you to bring into nuke and play around.

Finally I am adding in the original statue exr render, with some passes: beauty, depth, position, and normals, in case you want to try and color correct and match the statue render into any of these images or your own backgrounds. Thanks to Ernest Dios for the render.

Here is the dropbox link to the project files:
https://www.dropbox.com/sh/p47aquatmp1cai7/AAAnt_Lr4slT2RmK5znV50L3a?dl=0

So you’re thinking about making a switch to nuke?

July 27, 2013

VideoCopilot’s 04 tutorial is about the basic after effects interface, and so I thought I’d do something similar.  But instead of reinventing the wheel, I thought I’d just point you to some super useful Nuke tutorial “playlists” if you will where you can quickly learn the basic interface and workflow within nuke.

Here are some links to help you guys pick up the Basics:

for just basics:
http://www.thefoundry.co.uk/training/display_training_articles.php

For some broader tutorials  use this:
http://www.thefoundry.co.uk/products/nuke/training/
That page is really all you need to know, but hey, why stop there?

https://vimeo.com/channels/nuketutorials
tons of great videos there.

http://www.lynda.com/Nuke-5-tutorials/essential-training/60815-2.html?utm_medium=viral&utm_source=youtube&utm_campaign=videoupload-60815-0103
Also a great free resource!

I just found this one to be handy for users coming from AE or other comp programs to get a general sense of what nuke can do and some interface tips/tricks. It’s even called “STEP up to Nuke”:

https://vimeo.com/channels/504937/62598857

Hope all those sites and videos will hold your thirst of knowledge for awhile.  Shamefully, I haven’t even seen all these incredible videos yet, there are tons!  Slowly but surely though, I will plow through them all.

Knowledge starts with the heart.  So get passionate!

Thanks,

Tony Lyons

Optimization in Nuke

July 26, 2013

Hey Guys,

Different artists have different workflows.  But I think most can agree on common practices that make nuke run faster, and stay more organized, allow you as an artist to do your thing and output renders quickly.

I have my own list of Steps I have written sort of as a compositor’s Checklist.  I believe I posted this checklist in a blog awhile back, but I will give you guys the link to check it out.  I strongly suggest you write these down and keep them on your desk at work.  It is invaluable when you are starting out.  The blog was down so I’ll just post it here:

Compositor’s Checklist 

1.) Check your reference well (placement, timing, color, lighting, etc.)

2.) Flip back and forth/compare between the original plate and your render (or end of your script)

3.) Check Comp and elements in different LUT’s to check any problems across a wide range of color and values (basically testing to see if DI will mess up your shot by crunching values)

4.) Remember to Re-distort your CG, Also remember to undistort a plate before projecting it inside nuke. (these both assume you have a layout or matchmove geometry and camera that was exported from a program that tracked an undistorted plates)

5.) Try to limit the amount of grain nodes to 1 at the very bottom of the script, and use a “combined alpha” in order to mask where the grain should go. ***tip gamma up the channel being used as the mask, as a falloff in the mask will result in “soft grain”, which can reveal seams.

6.) Delete most or all nodes in your script that are unused or off to the side, if its something you think you’ll need later, just version up.

7.) Try to do test frames, test renders with jpgs at a lower quality first, to get a sense of timing or things that are immediate red flags. At the very least, render out first, middle and, last frames before committing to a lengthy render.

8.)AutoCrop whenever you can, keep your bounding box as small as possible on every element. In the spine of your script you’ll usually want the bbox to remain the size of your plate. For more info and a much better explanation go here: 

http://www.nukepedia.com/written-tut…ent-workflows/

9.) Use a saturation keyer at the end of the script to make sure cg isn’t overly saturated compared to the plate.

10.) When match specs, gamma down and match the CG spec to the plates natural spec, try to pick an area of that plate thats got similar spec already, if possible

11.) always gamma up to check blacks and shadow color

12.) Bring in previous renders so you can compare the current version to older versions, and that the proper notes were addressed.

13.) Note the kind of lens being used on the plate, judge depth of field based off how much defocus there is in the footage.

14.) make your own mattes in CG passes using a combo of combining mattes provided, huekeyer, and some rough roto, then pump it into the stream with it’s own channel so you can use it later on.

I am also going to link you guys to the 2 most useful articles about nuke optimization I have read online.  Both have saved me tons of render time and have made my scripts more organized and easy to navigate.  Links Down Below.

http://www.nukepedia.com/written-tutorials/10-tips-to-optimising-nuke-and-creating-efficient-workflows/

http://www.nukepedia.com/written-tutorials/compositing-practices-101/

Advanced Random-Lighting Match Tutorial

July 18, 2013

 

In this tutorial I go through a great technique for matching elements or CG to a plate that have randomly changing lights.

You will be able to quickly match whitepoints and black points to help seamlessly blend your image together.

Don’t waste your time animating grades when there is an automated technique that will get you 90% of the way there!

Cheers,

Tony Lyons