Nuke Tips – Kronos, MotionBlur, Oflow, or VectorBlur?

The last draft for this article dated back to Jan 25, 2016… time to revive it!

Kronos, MotionBlur, Oflow, or Vector Blur? I’m blur…

The great thing with Nuke is that we have many ways to skin a cat problem.

I’ll be focusing on adding motion blur to CGI FX elements like fire, blood and debris. Yes you can abuse I mean use Kronos and Oflow for adding motion blur instead of slowing down footage!

Time to explore the various methods and see which one make or break depending on the situation.

Do not get confused with MotionBlur2D and MotionBlur3D which are not designed to generate motion blur by analysing the image sequences. MotionBlur2D uses the Transform animation while MotionBlur3D uses the camera animation to generate motion blur.

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Nuke 1001 – Practical Compositing Fundamentals (3DCG)

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Practical Compositing Fundamentals for Everyone

In this tutorial, you’ll learn practical compositing fundamentals and the typical process that a Nuke compositor faces in a small project. At the end of this tutorial, one will be able to do a quick compositing (aka slap comp) and fine tune the final result with flexibility based on feedback from supervisors/directors/clients.

For this project, the task involves creating a believable rack focus shots of hundreds of teapots. Given the nature of team work in the industry, the 3DCG renders has been done by the 3D team and it is the compositor’s role to take the various render elements from it to be composited into the desired results.

Again, the goal of this tutorial is to show the fundamentals in a compositing and remember that every facility has their own compositing pipeline but nonetheless shares a common fundamentals in any compositing tasks be it 3DCG, live action or motion graphics.

Compositing for 3DCG

While I’m not a dedicated compositor at my current workplace (my current job involves creating FX elements such as fire, smoke, debris or blood), any FX artists need to know the process of creating a “slap comp” to see if their FX are integrated nicely into the scene.

As mentioned above, we’ll need to create a rack focus animation of the hundreds of teapots and this can be achieved through compositing (with the help of the AOV (Arbitary Output Variables)
aka render elements from the 3D renderer).

Before we proceed, the important skill of a compositor (and pretty much any jobs in this world) is problem solving and being resourceful. To keep things simple for this tutorial, everything
are prepared in a “perfect case scenario” but do keep in mind that in the industry, things often goes awry from my experience (I can’t comment on Western-pipeline studios but it is common occurrence for Japanese-pipeline studios as my workplace is an outsource studios for many Japanese AAA projects).

Basically, prepare to die I mean sacrifice lots of time and money when you just starting out in this industry.

So with that out from the bag, let’s proceed to the actual compositing in Nuke!

(well this tutorial is applicable to other compositing software like After Effects, Fusion, Flame or gasp Shake except you will need to search for the equivalent functions in the respective software)

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Recreate After Effects Settings in Nuke (and vice versa)

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Note: I will update this post regularly with more settings with the proper graphic comparison between both software.

Recreate After Effects Settings in Nuke? Why?

Lately, I’ve been practicing an odd pipeline that I develop myself to improve my productivity (although my colleagues thinks I’m crazy).

After Effects (AE) is the main (and only) compositing software for the project that I’m currently involved and there are several reasons why I loathe it during production:

  1. Heavy use of EXR multichannels which are a pain to manage in AE (the Create ProEXR Layers will forever haunt me)
  2. No easy way to share and reuse mask across multiple layers.
  3. The roto tools are not as robust as in Nuke.
  4. You can’t see which effects are being applied to a layer until you select it.
  5. Unpremultiply/premultiply process is still a chore in AE unlike Nuke.
  6. Lastly but not related to AE, the in-house motion blur plugin that we must use (read: forced) suffer from memory leak which gobble up all the allocated RAM for AE.

So my odd pipeline involves Nuke as my first step in compositing my FX works and transferring it to AE once the cut are approved by the director for use by the compositing team.

To ensure that the settings between both software can produce the same result (or as close as possible), I’ve done many trials and errors and has been proven ready for actual production (at least I’ve haven’t been caught yet–).

WARNING: Make sure your AE project settings is set to 32-bit Float and sRGB working space (or etc) with the Linearize Working Space checked to match the results as close as possible to Nuke.

Levels (AE) and Grade (Nuke)

Grade node in Nuke is similar to AE Levels.

  • Grade Blackpoint is Levels Input Black
  • Grade Whitepoint is Levels Input White
  • Grade Lift is Levels Output Black
  • Grade Gain is Levels Output White
  • Grade Gamma is Levels Gamma

For offset, the function is similar to the offset found in AE Exposure effects.

Hue/Saturation (AE) and HSVTool (Nuke)

The HSVTool parameters match the one used in Hue/Saturation. I made a huge mistake in using HueShift initially in Nuke to recreate the settings of Hue/Saturation.

Time Remapping (AE) and TimeWarp (Nuke)

Both of them does the same thing except that in Nuke, you need to set the TimeWarp filter to None to get the same result as Time Remapping in AE.

Opacity (AE) and Mix (Nuke)

The Opacity function of a layer in AE is the same as the Mix slider of a Merge node in Nuke.

Matte Choker/Refine Hard/Soft Matte (AE) and Erode (Nuke)

Both of them does the same thing except I found Erode to be more intuitive compared to Matte Choker. Be careful though as Matte Choker is not 32-bit ready in AE so it will clamp the pixel values to 16-bit Half Float.

Alternatively, you can use Refine Hard/Soft Matte as it is 32-bit ready although it can be too slow to my liking.

Box/Fast/Gaussian Blur (AE) and Blur (Nuke)

Seriously, you should stick to either Box or Fast Blur in AE if you’re planning to transfer settings from Nuke as Gaussian Blur is pretty limited. Stu Maschwitz’s A Tale of Three Blurs explains it in-depth for each Blur filter in AE.

More to come.