Computer graphics are one of the most exciting and interesting areas in computer science. In short, the term computer graphics includes almost everything on a computer that is not text or sound. This includes simple things like windows, menus, and text, as well as more complex images like three-dimensional models and video sequences. From video games to 3D animation, a lot of it is built on the foundations of computer graphics. This post is a personal archive of my notes from reading Scratchapixel's post 

A Gentle Introduction to Computer Graphics (programming)

When starting to look into a topic such as computer graphics, it can be a little intimidating to dive given the amount terms used to discuss the topic. I've compiled this short list of terms from my readings. 

 The further away an object gets the smaller it becomes.

: The combination of two images from slightly different angles used to approximate the distance and the position of objects in a 3D space with respect to each other.

: A coordinate system that specifics each point uniquely by a pair of numerical coordinates.

: How points are connected to form faces.

: A composed image that are 3D in appearance. Usually triangular but not always. They appear when a surface is modeled, vertices are selected, and the object is rendered in a wire frame model.

: A 3D object representation consisting of a collection of vertices and polygons. A 3D object representation can be a polygon mesh.

: The projection of the corners of a shape onto an imaginary canvas.

 The region of space in the modeled world that may appear on the screen. You can also think of it as the field of view of a perspective virtual camera.

 When the point produced by the perspective matrix multiplication has a non-unitary 4th component that represents the perspective divide by z. This divide of each point by its 4th component completes the perspective transformation.

 The projection of the camera space into a 2D coordinate system.

: The process that changes the range of pixel intensity values. To normalize something is to remap the values from any range to a range of [0, 1]

: Rendering that is not limited to a time constraint. Rendering offline is basically preparing a scene for rendering which the result will be viewed offline once the render is complete.

: Rendering that started the moment we ask for it. Commonly seen in video games where we have to render each frame during game play.

We need vertices and topology before we create the image of the 3D scene.

Rendering is a critical part of the creation of 3D images.

Geometry is very important as it allows us to handle object transformations (scale, rotation, and translation). It also allows us to handle the computation of angles between lines or to find out the intersection between a line and other shapes.

When animating a shape, it has to be re-rendered at each frame.

Common computational tasks include, rendering and simulations.

The more geometry a scene has, the more expensive that computational task becomes.

Computer graphics are used in a variety of fields, including advertising, architecture, art, automotive design, biomedical visualization, computer-aided design (CAD), computer games, education, entertainment, film, video post-production, virtual reality, etc. The landscape is consistently changing with new tools and technology coming out to simplify the creation of 3D products. It can be a little intimidating to jump into the industry given the amount of options that exist today. However, I would say that is the best part about computer graphics.

A small collection of notes from my studies of computer graphic basics

Intro to computer graphics

USD (Universal Scene Description) is a framework that was developed by Pixar to improve the collaboration between technical and creative by moving from a sequential workflow to a collaborative workflow. The (.USDA) file type is used in a variety of programs like Maya, Omniverse, Unity, and Unreal Engine.

The USD file type has access to the sublayers, references and variants of a project.

Each department with pixar used to have different apis to do the things they do.

A single USD file can contain meshes, lights, shaders, camera information, etc.

The USD file type can have multiple representations like .USD, .USDC , .USDA , and .USDZ

The 6 kinds of composition arcs in USD files are sublayers, reference, payloads, variants, inherits, and specializes.

Rendering architecture for images from USD

Supports rendering backends like OpenGL and RTX ray tracing.

: The primary container object in USD. Prims can contain other prims, creating a namespace hierarchy.

: The ways in which USD files can be combined together.

: The outermost container for scene description.

: The other kind of namespace object in USD. There are two types of properties (attributes and relationships).

: A namespace pointer. Relationships can have multiples targets.

: An object that authors and retrieves structured data from some UsdObject.

: The atomic persistent container of scene description for USD.

: The keystone to understanding composition in USD. It is the ordered set of layers resulting from the recursive gathering of all SubLayers of a Layer, plus the layer itself as first and strongest.

: The composition arc used to construct LayerStacks.

: The composition arc that can be used to achieve a similar kind of layering data, when one knows exactly which prims need to be layered.

: The composition arc that is a kind of reference. Payloads are weaker than references and given a LayerStack, all direct references will be stronger than all direct payloads.

: The composition arc that allows a content creator to package a discrete set of alternatives, between which a downstream consumer is able to non-destructively switch, or augment.

: The composition arc that addresses the problem of adding a single, non-destructive edit that can affect a while class of distinct objects on a stage.

: The composition arc that allows a specialized prim to be continuously refined from a base prim, through unlimited levels of referencing.

https://graphics.pixar.com/usd/release/index.html

https://graphics.pixar.com/usd/release/glossary.html

A compilation of my notes from studying USD.

Blog Posts

Intro to computer graphics

Intro to USD