Lesson 1 : Compositing basics

Welcome to the exciting world of digital compositing with Foundry's Nuke!

In this course, we will dive into the fascinating universe of visual post-production, where imagination becomes reality through the art of combining visual elements to create stunning and cinematic images.

Table of Contents

1. Compositing Basics
2. Node Families
3. Workflow Organization
4. Sources

1. Compositing Basics

Nuke, the go-to tool for cinematic and television post-production artists, is a powerful compositing platform that offers unparalleled flexibility and advanced features for creating high-quality visual effects. Whether you aspire to create spectacular digital landscapes, integrate characters into fantastic worlds, or perfect film sequences, this course will provide you with the knowledge and skills necessary to bring your creative ideas to life.

Throughout this program, we will explore the fundamental principles of compositing, advanced image manipulation techniques, and efficient workflows to optimize your work in Nuke. Whether you are a beginner seeking to master the basics or a professional looking to deepen your knowledge, this course will provide you with a solid foundation to excel in the thrilling art of compositing with Nuke.

Games of trones, saison 8, HBO, 2019

Compositing bases:

What is Compositing?

Compositing is a technique used in the film, television, advertising, and special effects industries to combine multiple distinct visual elements into a single image or video sequence. Essentially, it involves creating a final composition from different elements such as filmed footage, computer-generated imagery (CGI), special effects, animations, backgrounds, and more.

The goal of compositing is to create a harmonious and realistic visual rendering by integrating these elements in a coherent manner. This can include tasks such as adjusting colors and lighting, incorporating special effects, creating matte paintings (digital scenery), adding or removing objects, correcting imperfections, and much more. It is the last department in terms of CGI, often combining with lighting, and it is common to see Lighting/Compositing artists.

Compositing plays a crucial role in creating impressive visual effects and stunning cinematic images. It often requires the use of specialized software tools such as Nuke, After Effects, and others, as well as a solid understanding of the fundamental principles of visual composition and aesthetics.

Showreel 2022 by Foundry

Nuke Interface

The Nuke interface is designed to provide a smooth and intuitive working experience while offering quick access to the tools and features needed for compositing and visual post-production. Here is a general description of its main components:

Viewer: This is where you view your images and compositions. Nuke offers multiple viewers to display different types of outputs, such as the main view, alpha view, individual channel views (Red, Green, Blue), and more.

Node Graph: This is the heart of Nuke. In the node graph, you create and organize your nodes to build your visual composition. Each node performs a specific operation, such as reading an image, applying an effect, or adjusting colors.

Toolbar: The toolbar provides quick access to commonly used tools and commands, such as creating nodes, navigating the composition, and display options.

Properties Panel: This panel displays the parameters and properties of the selected node in the node graph. You can adjust these parameters to modify the node's behavior and customize your composition.

Node Bin: The node bin contains a collection of predefined nodes that you can drag and drop into the node graph to add functionality to your composition.

Timeline: The timeline allows you to manage the chronology of your composition, adjust the timing of video clips, keyframes, and temporal effects.

Curve Editor: This tool lets you manipulate animation curves to control animated parameters such as position, rotation, scale, and more.

Script Editor: You can use the script editor to write scripts in TCL (Tool Command Language) to automate tasks or customize Nuke's behavior.

Together, these components offer a powerful and flexible working environment for creating visual effects and post-production, enabling artists to produce high-quality visual compositions with remarkable efficiency.

Toolbar

Viewer

Node Editor

Properties Panel

2. Node Families

Whats is a node ?

Nodes are the basis of everything Nuke does, as in Houdini, for example. They're called nodal software. When you create geometry, color settings, etc., you'll need to use nodes. Nodals record the actions you've performed and the parameters you've used. You can go back in time and modify the parameters and selections of existing nodes to edit the creation history of your scene.

The power of nodal is that nothing is fixed, so you're free to change any aspect of your hierarchy quickly. it's a non-destructive workflow. A node is made up of several calculations, the succession of operations by other specific nodes that serve to create the primary nodes you use.

We can see this clearly in Houdini: when we double-click on a node, we have access to the work of the developers at side FX, so we can see how the node was designed :

Node Guide Groom

In the Node Guide Groom

In Nuke, different types of nodes are grouped into several families, each designed to perform specific operations in the compositing and post-production process. Here is an overview of the main node families in Nuke:

Shuffle:

Shuffle: The Shuffle node is used to extract specific channels from an image and remap or rename them as needed. For example, you can use a Shuffle node to extract the alpha channel from an image or to separate the color channels (red, green, blue) for individual manipulation.
LayerContactSheet: This node displays different AOVs (Arbitrary Output Variables) in the viewer, which is quite practical for viewing the entirety of an EXR file.

Merge:

The Merge node in Nuke is one of the most fundamental and powerful tools for combining visual elements in a composition. Here is an overview of its functionality and main uses:

Combining Images: The Merge node is used to combine multiple images or visual elements into one. For example, you can use a Merge node to overlay characters onto a background, integrate special effects into a film sequence, or add graphic elements to a video.
Opacity Control: The Merge node allows you to control the opacity of each merged element, enabling you to adjust the transparency and intensity of the layered elements. You can also use opacity masks to define areas of variable opacity in the final image.
Blend Modes: The Merge node offers a variety of blend operations to combine visual elements, such as add, subtract, multiply, divide, minimum, maximum, and more. These blend operations allow you to precisely control how the pixels of different layers are combined.
Alpha Channel Control: The Merge node supports the manipulation of alpha channels, allowing you to compose images with variable transparency areas. You can use opacity masks or built-in alpha channels to control the visibility of overlaid elements.
Advanced Blend Modes: In addition to basic blend operations, the Merge node supports advanced blend modes such as Photoshop-style modes ("Screen", "Multiply", "Overlay", etc.), enabling you to achieve creative and artistic results.

In summary, the Merge node is an essential component of the compositing process in Nuke, offering flexibility and precise control over how visual elements are combined to create realistic visual compositions.

Color:

Color nodes in Nuke are used to adjust and manipulate the chromatic aspects of images, offering precise control over the colorimetry and visual appearance of the composition. Here are some of the most commonly used color nodes in Nuke:

Grade: The Grade node is used to adjust the color, brightness, contrast, and gamma parameters of an image. It also allows selective modification of RGB channel values and the application of global or local corrections to the image.
ColorCorrect: The ColorCorrect node offers an extensive range of tools for performing precise color corrections. It allows you to adjust hues, saturations, and color values, as well as apply color corrections based on masks and selections.
ColorLookup: The ColorLookup node is used to apply LUTs (Look-Up Tables) to an image, enabling quick modifications to its appearance by applying predefined or custom transformations. This can be useful for applying specific color styles or matching the visual appearance of other sources.
ColorCorrector: This node provides various tools for adjusting the colors, contrasts, and brightness ranges of an image. It also allows for color corrections based on masks and selections, as well as working with individual channels for selective adjustments.
Colorspace: The Colorspace node is used to convert images between different color spaces, ensuring precise color matching when manipulating images from different sources or intended for specific outputs.
HueCorrect: This node allows for selective adjustment of hues and tones in an image, useful for correcting color deviations or applying creative color grading effects.

These color nodes offer a wide range of tools and functionalities for manipulating and adjusting the chromatic aspects of images.

Masking and Keying:

Keyers and masking tools are essential in Nuke for performing precise cutouts, extracting specific visual elements from an image, and creating realistic composites. Here is an explanation of these tools:

Keylight: Keylight is one of the most widely used keyers in Nuke. It is designed to extract elements from an image based on luminance or chrominance. Keylight offers a range of tools to adjust key parameters such as color tolerance, spill suppression, and edge refinement.
Primatte: Primatte is another popular keyer in Nuke, used to extract elements from an image based on luminance, chrominance, and saturation. It provides a user-friendly interface with intuitive controls to adjust key quality and refine edge details.
Ultimatte: Ultimatte is an advanced keyer designed to extract elements from an image while preserving fine details such as hair and fur. It offers sophisticated tools for adjusting the key, including options for handling spill and reflections.

Masking Tools:

Roto: The Roto tool is used to create manual masks and shapes on images. It allows artists to define custom shapes to isolate specific elements of an image and use them as masks for compositing.
Bezier: The Bezier tool is an advanced version of the Roto tool, offering more precise and flexible curve drawing capabilities. It enables artists to create complex masks with smooth curves and adjustable control points.
Keymix: The Keymix node is used to combine images using alpha masks. It allows blending multiple images based on the transparency defined by the masks, providing precise control over how different layers are composed.

These keyers and masking tools provide artists with a comprehensive range of tools for performing precise cutouts and creating realistic visual composites in Nuke. By using these tools creatively and judiciously, artists can achieve complex and impressive visual effects.

Tracking:

Tracking in Nuke is an essential feature that allows you to follow the movement of objects or points of interest in a video sequence. Here is an overview of the tracking capabilities in Nuke:

Tracker Node: The Tracker node is used for 2D tracking on specific points in a video sequence. It tracks the movement of selected points across multiple frames, calculating transformations such as translation, rotation, scale, and deformation.
Planar Tracker Node: The Planar Tracker node is used for planar tracking, meaning it can track the movement of a flat surface in a video sequence. This allows tracking objects like billboards, computer screens, walls, etc., and applying visual elements to that surface realistically.
CameraTracker Node: The CameraTracker node is used for 3D camera tracking in a video sequence. It analyzes the camera movements in the sequence and reconstructs the scene geometry in 3D, enabling precise integration of virtual elements into the sequence.
Stabilize Node: The Stabilize node is used to stabilize a video sequence using tracking data. It compensates for camera or object movement in the sequence, which can be useful for stabilizing shaky footage or creating visual effects like element insertions.

By effectively using these tracking tools, artists can follow the movement of objects in a video sequence, integrate visual elements realistically, stabilize footage, and create impressive visual effects in Nuke.

3. Workflow Organization

AOVs (Arbitrary Output Variables):

AOVs and integrators are key elements in the 3D rendering process that allow control and customization of the visual output in computer-generated images. When you export an image as an EXR (OpenEXR) file from rendering software like Arnold, V-Ray, Redshift, etc., you can include multiple AOV channels along with integrator-specific information for later use in Nuke or other compositing software. Here’s an overview of these concepts:

AOVs (Arbitrary Output Variables):

AOVs are additional output channels generated during the 3D rendering process that contain specific information such as depth (Z-depth), surface normals, diffuse passes, specular passes, reflection passes, refraction passes, material passes, etc.
Purpose: AOVs allow artists to control different visual aspects of the 3D scene separately during the compositing phase. For example, you can individually adjust the brightness of reflections or shadows or apply specific effects to certain elements of the scene.
EXR Export: When you export an image as an EXR file, you can choose to include relevant AOVs based on the specific compositing needs or visual effects you want to achieve in Nuke.

AOVs Renderman, to manage aovs it's quite similar on Arnold.

AOVs very useful to decompose your beauty

Teapot Example :

With the example of the teapor we'll take out the 4 primary AOVs :

- Direct Diffuse

- Direct Specular

- Indirect Diffuse

- Indirect Specular

Beauty

Specular

Diffuse color

Indirect Specular

Indirect Diffuse

You can check your AOV's here before export.

The contactsheet node displays all aovs in an EXR export.

You can check the Lesson 6 in Lighting : Rendering and Compositing , if you want to know more about AOVs !

Integrators:

There are different types of integrators, for instance, in Renderman, many AOVs can be found which give a lot of freedom in compositing. Notably, exporting 3D data from the image.

Pworld: 3D coordinates, masking fixed areas by camera movement, matte painting, placing 3D noise, environment light, etc.
Nworld: Creating masks from normal information, relighting in composition (no shadows), faux glass with idistort.
Stmap: Apply a texture with the stmap node (be careful with UDIMs) for cleaning up jagged edges.
Pref: Create "texture reference position" in Maya, a world baked onto the character that follows the animation. This can be useful in certain situations.
Z from Renderman is aliased: Use it for Zdefocus.
__depth is antialiased (Red channel): Remap it, combine with stock shots/noises, and create fog.
__depth.blue: This is the Fresnel or orientation ratio, excellent for creating magical effects, can be used for ghosts, reflections, etc. Edge detect gives good results.
motionFore: Vector blur or other effects that occur in motion.

When you export an image as a float EXR file, the information about the integrator used to calculate the render can be included in the file’s metadata. This can be useful for understanding the rendering parameters used and adjusting the compositing settings accordingly in Nuke.

In summary, AOVs and integrator information included in EXR files allow artists to control and customize the visual aspects of 3D renders during compositing in software like Nuke, providing great flexibility and higher quality in creating visual effects.

Integrator Teapot

Backdrop and Stick Nodes:

Backdrops and Sticky Nodes are two important features in Nuke that facilitate the organization and visualization of complex compositions:

Backdrop:

Purpose: Backdrops are graphical elements that visually group related nodes in Nuke’s Node Graph.
Organization: They help organize and structure the composition by grouping associated nodes, making the composition’s structure clearer and more intuitive.
Creation: You can create a Backdrop by selecting multiple nodes in the Node Graph, then using the corresponding command in the context menu. You can then name and color the Backdrop and add notes for better understanding of the composition.
Manipulation: Backdrops can be moved and resized easily and can be locked to prevent accidental modifications to the composition.

Sticky Nodes:

Purpose: Sticky Nodes are special nodes attached to a Backdrop and remain associated with it when the Backdrop is moved or resized.
Functionality: They are useful for adding additional functionality or notes to a Backdrop without directly associating them with specific nodes in the composition.
Content: Sticky Nodes can contain notes, comments, instructions, annotations, or other useful information to document the composition or explain its functionality.
Attachment: You can add a Sticky Node to a Backdrop by dragging and dropping it onto the Backdrop, then customizing it as needed. It stays associated with the Backdrop even if the Backdrop is moved or resized.

By combining Backdrops and Sticky Nodes, artists can effectively organize, document, and visualize complex compositions.

In the next lesson, we will learn how to set up and discover new useful tools for compositing.