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Tag: Compositing

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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

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

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.