Tutorials

SVG5: More Transforms and Composition

in SVG Tutorials
svg
This is part 5 of the 6 part SVG tutorial Most of the things I’ve seen about SVG on the web are meant for designers who haven’t had a graphics class, so they are a little vague about transformation. The specification has all the details (including all of the kinds of transforms that are supported). However, it doesn’t specify how composition occurs. SVG does allow transformations to be composed. You can put multiple transformations on any object. Read more…

Image-based vs. Object-based Graphics

in Tutorials
There’s a very basic distinction in kinds of pictures (and therefore kinds of graphics) we use with computers. The difference is really simple, but very difficult to describe precisely. In fact, we don’t even have great words for the two categories. In the old days, they referred to the two types as “raster” and “vector”. I prefer “image-based” and “object-based”. Here’s a first attempt at the definitions: An image-based (or raster) graphic represents the pictures by measuring the color at a pre-determined set of locations (usually a grid). Read more…

Color: Initial Answers to a Practical Question

in Tutorials
Color is complicated. There is a ton of stuff to learn. Later in class, we’ll discuss color more – and just scratch the surface of its complexity. But, between now and then you need to make pictures and you will want to specify what colors are in them. So here’s a short version… Can I really represent Color as 3 Numbers? In terms of the physics of light: you cannot. In terms of the perceptual science (psychology): in theory, 3 numbers are sufficient to capture what people can see. Read more…

Points, Vectors and Coordinate Systems

in Tutorials
It always bugged me that math books made a big deal of the difference between points and vectors. They’re both just a list of numbers, right? In practice, yes, they are both lists of numbers. But getting an idea of what the difference is helps develop the intuition of coordinate system. To describe this, let me use an analogy/example: describing walking in a room. Assume that you know which way is north. Read more…

What is a Pixel? (and what is a point sample?)

in Tutorials
When we talk about image-based graphics, we talk about it being a regular collection (usually a grid) of samples (or pixels). It’s time to be a little more precise about this. The term pixel is (I’m told) short for the term “picture element.” (Wikipedia, of course talks about this) Unfortunately, there is an ambiguity when we talk about a grid. And for reasons that we become clearer later, it is better to think about pixels one way rather than the other. Read more…

Object Oriented Programming in JavaScript, Part 2

in Tutorials
This is part 2 of our 2 part tutorial on “Traditional” Object Oriented programming in JavaScript. The tutorial was written by the course staff in 2020, but updated in 2021. In the first part of this tutorial ( Traditional Object Oriented Programming in JavaScript), we showed you how to use JavaScript’s class syntax; this time, we’ll take a look at how we can use it to do the things you’re used to in object oriented programming: inheritance, polymorphism, and more. Read more…

Traditional Object Oriented Programming in JavaScript

in Tutorials
This tutorial was written for CS559 2020 by the course staff, and updated for 2021. JavaScript has many different mechanisms for doing object oriented programming. Many of them are hard to learn. They are very general, but require effort to implement common idioms (like classes). Fortunately, newer versions of JavaScript (like we use in class) give us another option that provides a convenient syntax for “traditional” (class/instance style) object oriented programming. Read more…