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Tag: Nuke

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Gonzalo - Nuke VFX Fundamentals

28/11 3D Matchmoving

3D Tracking in Nuke

There is an additional axis involved for 3D tracking in Nuke.

You can extract cameras, and position information in Nuke.

From Nuke version 15, there is support for USD file format.

Axis in Nuke is a null/locator.

Tab in the viewport to switch from 2d to 3d view.

Basic UI/UX navigation is similar to most DCCs.

Pixel Analyzer.

Workspaces can be customised as well.

grains more in darker areas, lesser in the brighter areas

.dpx is an older image file format

renders from CG should be clean and free of noise, grain workflow will be done in post-production

Scanline Render/Camera/Sphere

multisample tab to adjust the sample size, to adjust the quality of the render

3D Geo, Lights and Materials

All 3d objects exist here in the 3d scene node

Lens Distortion

All camera footage is shot through a lens. A lens is a series of curved pieces of glass that bend light and “focus” the rays on the image plane.

Lenses with different focal lengths produce different lens distortion and even with the same focal length, no two lenses are the same.

24mm lens, more lens distortion at the edges
50mm lens, less distortion

Workflow for compositing, undistort-> doing comp work -> bring back lens distortion afterwards

DP on the production site will take down lens information, and take a picture of the distortion grid to record the distortion.

Other information recorded on set will include, chrome and matte balls, Macbeth chart, and 360-degree image for HDRI.

Lens distortion
Only in NukeX
undistorted image
Difference

For plates without any grid, we need to manually draw those lines. Both vertical and horizontal guidelines need to be drawn. One line needs to have at least 4 points to be considered a guide.

STmap

Works with Nuke. Also lighter with STmap.

STmaps move pixels with a texture map (U,V) with green and red channels.

Also, know as a forward channel for undistortion and backward channel for distortion.

Assignment: Balloon Festival

This is my final product for my Nuke term assignment. I will do an individual post to cover the process.

Reflection

Today is the last day of the workshop style class as Gonzalo is not going to cover any more compositing until the next term, we were given a sneak peek into what we are going to cover for next term which is 3D match moving. Also, we reviewed our Balloon Festival assignment. We covered the 3D aspect of Nuke and learned about len distortion and how we work with footage with distortion.

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Gonzalo - Nuke VFX Fundamentals

21/11 2D Cleanup

The Rotopaint node has more added features compared to the roto node.

A little similar to Photoshop.

Operations:

Brush – unlike Photoshop, there is no custom brush. We can paint with blend modes as well.

Clone – Hold ctrl to sample and paint, and shift to adjust the brush size.

Use lower opacity for a more refined result. adjust brush edge hardness when needed.

Blur – similar to Photoshop blur

Dodge and burn – for painting in shadows with burn and highlights with dodge.

Can set either single frame operation or entire frame range.

All edits are recorded in the node and can be further edited. parameters that can be edited such as transformation, stroke, lifetime, and shape.

Rotopaint can also generate custom-painted alpha channels, just need to enable in the hidden folder

Difference node helps to isolate the difference between two images.

For clean up, we need to denoise the plate because the cleanup will stand out on the plate with grain. Normal workflow would be to denoise the plate first, do the clean up then re-introduce the grain.

Match grain by channel.

Grains are super important as they occur in almost every shot

F_regrain samples an area (the flatter the area the more stable) then applies a similar grain pattern) only NukeX.

Kodak Grain, sets grains by RGB channels, normally the biggest grain is in the blue channel.

Need to match-move before applying the cleanup.

Homework assignment: do before and after, do more damage.

Tips for hand-painted motion blur and smear

motion blur
smear

Grains/Noise

Grain can be extracted by using the minus operation for the original plate with the denoised plate.

Changing from linear to cineon color spaces will reveal more grains in the darker areas, purely for visualisation purposes.

Cons: will work on flat sections of the plate. but will not work for uneven surfaces because of the way the grain is distributed and arranged.

Newer workflow is done using the DasGrain gizmo by Fabian Holtz

Localised grain application, with common_key and DasGrain node.

Normalise grains, as grains are not even spread throughout the plate.

Grains more in darker areas, lesser in the brighter areas

Gizmos can be copied and pasted and shared, they are just Python codes.

Reflection

Today we learnt about roto paint tool to do some clean up to the plate. For assignment we are suppose to do a messy class corridor scene. I feel like the given examples gives me a haunted vibe. So why not just add a floating “spirit”(its actually Dark Sun Gwyndolin from Dark Souls)?

I create the scene in 3D then place various 3d models i found online. The main character also has a smoke simulation to it on top of the floating animation. I also tried to match the lighting as much as possible. Then I rendered out the scene.

Finally, I composited everything in Nuke and graded it. Of course not forgetting the main point of the class is to do some clean up. I covered up some of the pasted posters and added some graffiti on the walls as well.

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Gonzalo - Nuke VFX Fundamentals

14/11 Channels & Planar Tracking

Recap: Ctrl mouse click to the viewer will sample pixel details on the frame, Ctrl+shift will sample the average pixel detail on the screen

Filtering

Reformat:

When scaling up an image, do not scale it more than 10%. If not the image will start to lose details and become softer.

https://www.topazlabs.com/ good upscaling software

Concatenation

Concatenation is the ability to perform one single mathematical calculation across several tools in the Transform family. This single calculation (or filter) allows us to retain as much detail as possible.

Do not break the concatenation, it blurs the image. It happens when adding nodes with filtering (transforming).

Filtering (and Motion blur) is recognised only at the end of the node tree.

BBOX ??

Shuffle node

A powerful node that allows the manipulation of different colour channels (as well as other AOVs) to the output result.

AOVs can also be accessed in the shuffle node

TIP: For animation ease, select keyframe and press H.

Planar Tracking exercise

Defocuse with depth pass, Use defocuse instead of blur.

Zdefocus gives more control as it utilises the depth pass. There is an option to control the focal point apart from the size of the blur.

Native to nuke, we can render out 3D objects with depth pass as well to apply defocus.

Bokeh, added to nuke on plugin from v14 onwards. It reads real camera values. The node is really good based on the inputs. But very slow. only in NukeX only.

Assignment: iPhone Planar Tracking

Reflection

Today we did a bit if planar tracking exercise, we are suppose to track and mask out the fingers on the phone. The brief was to stablise the shot and create an interesting animation of the screen reacting to the movement of the fingers. Using tracking and stablising, I was able to create a mask area to replace the screen with a interactive iphone screen. I used a bit of houdini to simulate a cloth drag for the first swipe and particle simulation to show the second swipe.

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Gonzalo - Nuke VFX Fundamentals

07/11 2D Tracking

Transform model

2D track – flat

2.5 track – parallax

3D track – pure 3D

2D tracking workflow:

add tracker node

make a new tracker, and place it at one corner of the TV

the first box searches within, and the second box is the search limit

Play track, and export match move one point. this creates a new transform node that links to the tracker node and has the tracker data.

The order of the track location matters.

stabilising shots

Reflections

I have seen similar tracking methods in After Effects and it was quite popular a few years ago. It is a good start to build a foundation for 3d tracking. I had a lot of fun picking out the posters and placing them in the footage.

Assignment: Planar Tracking Street Poster

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Gonzalo - Nuke VFX Fundamentals

31/10 Merging + Color

Concept of Premultiplication

Softwares like AE already premult layers

Page Up & Page Down to scrub AOVs

Instead of a layer system, the node tree system is a list of instructions

Merge Node and its operations:

  • over
  • mask
  • average
  • overlay
  • stencil
  • minimum
  • maximum
  • under
  • etc…

Reformat node: changing image size/format. Upscaling will result in the degradation of image quality. You can choose the interpolation methods but the result is often jittery. Can look at AI tools if upscaling is really needed.

Premult Workflow: Unpremult to divide by alpha -> do grading and CC -> then premult

When doing grading, we process and treat RGB separately from Alpha channels.

Colorspace and linearisation

32 Bit Color

Colour Matching Methods:
1. Edit the white point of the original colour, then adjust the gain.

2. Divide color, then multiply

Ctrl Shift-drag to get an average colour data

Alt + K for cloning nodes creates a reference copy of the node with linkages for all the parameters.

QC

Control highlights, mid-tones and low

Reflections

Today the main takeaway for me is the concept of per-multipilcation. To do image edits, we need to unpremult before doing any operation to the image. This is because there is extra image data in the channels that we are not aware. This information is new to me and I will definitely keep this in mind the next time when I do compositing.

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Gonzalo - Nuke VFX Fundamentals

23/10 Rotoscoping

General Roto information

Rotoscoping for VFX is used to create a matte or mask for an element from a plate, so it can be extracted out to place on a different background or edited. Rotoscoping gives artists a chance to produce scenes that would otherwise be difficult to do in real life. It also allows us to edit out unwanted elements in post-production. the possibilities are endless.

Roto Node and Rotopaint are generally similar. Rotopaint allows you to paint on the plate. But the roto node is lighter.

Colour Channels & Alpha

Mattes can be located on each channel

Motion blur in mattes is important, and often roto mattes have motion blur included

Rotoscoping

Divide and conquer, split the subject into parts for the roto mask.

Lesser spline points will result in a smoother animated mask

Roto Assignment: Running Man

The assignment brief was to create a matte for the running man as well as the bridge railings from the plate. The following is my attempt at the assignment.

Reflections

Today we learnt about isolating specific elements within a plate into different layers. It involves creating an animated mask which is black and white so that we can use different pixel operations to extract them out from the background. I find that this is a incredibly tedious task. Although Gonzalo said it can be quite nice and easy to do, I find that my mind when numb when trying to shift those individual keys to create the roto masks. Perhaps my workflow is not that refined, but I did not enjoy the entire process. I also was not pleased with my final result of the running man as I see a lot of problems with my work. I will need more practice to get better.

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Gonzalo - Nuke VFX Fundamentals

17/10 Intro to Digital Compositing & Nuke UI

What does a digital compositor do?

Compositors create the final image of a frame, shot or sequence. They take different digital elements; like the animations, background plates, graphics and special effects (SFX) and put them together to make a believable picture.

General Pipeline of a film/movie

Pipeline workflow

Three routes in an established production company

  1. Technical Artist
  2. CG Generalist
  3. Compositor

Digital Compositor progression:

  1. Roto
  2. Prep
  3. Junior comp
  4. Mid comp
  5. Senior comp
  6. Lead comp/department head
  7. 2D sup
  8. VFX sup

Software for Compositing

After Effects

  • Layer based compositing
  • 8/16-bit colour, for broadcasting use
  • Most of the time, not computationally heavy
  • popular with motion graphics
  • Unstable performances with large data files, and other colour spaces other than sRGB
  • Missing features for digital compositing

Davinci Resolve

  • Node-based
  • better colour management
  • works well with heavy files
  • Free
  • Comp and grading in the same software

Nuke

  • Supports USD (universal scene description)
  • Customizable
  • Comes in different types
    • NukeX
    • Nuke Student
    • Nuke Non-Commerical
    • Nuke Indie
Differences across all nuke versions

Nuke

More information is available in the documents in the week 3 folder.

What was went through:

  • UI navigation
    • Toolbar
    • Node graph
    • Properties
    • Viewer
  • Some basic shortcuts
  • Nuke script format, open projects, save projects
  • Workspaces
  • Node groups
  • Commonly used nodes

Feedback

Wk2 Assignment

Comments: Pay more attention to telling the story. Need more direction.

Next week’s homework:

Practice and get comfortable with the software

Next class: Rotoscoping

Reflections

Today’s class is still covering a bit of theory. Gonzalo covered in detail what the job of a compositor entails and where compositing is positioned in the pipeline. He also covered the general progression of a digital compositor. We then moved on to talk about the differences between the different general compositing software in the different industries.

The later part of the class, we finally proceed to open nuke. Gonzalo very patiently introduced us to node based compositing with Nuke. He also covered some common nodes that we will be using often in our journey. He assured us that it is alright to not understand everything that he covered as it might be overwhelming at first, but eventually we will get it. I really like the pacing of his class as it was not too fast nor it was slow. I look forward to more Nuke classes as it seems interesting.