(Unit 0) Intro 1: Rendering

Summary

In this introductory lecture for Comp 3490: Computer Graphics One, the instructor delves into the foundational concept of rendering, which is the process of translating data into visual displays. The lecture emphasizes the importance of pixels, the smallest individually accessible display elements, predominantly squares but with alternatives like anamorphic (rectangular) and non-rectangular pixels such as hex pixels. The instructor also introduces raster graphics, explaining how they are composed of a grid of pixels, and touches on various file formats like JPEG, PNG, and BMP that are used to store these pixel grids. The lecture aims to provide students with a solid understanding of the basics of computer graphics, setting the stage for more advanced topics in the course.

Takeaways

• 🎓 The lecture is part of the COMP 3490 course on computer graphics, focusing on the basics and building blocks of the subject.
• 🖼️ Rendering is defined as the process of converting abstract data into a visual display on a screen, which is a fundamental problem in computer graphics.
• 🔍 The lecturer introduces pixels as the smallest individually accessible display elements, typically squares, but with alternatives like anamorphic and non-rectangular pixels.
• 📐 Anamorphic pixels are non-square, rectangular pixels used in certain displays like TVs where one dimension is more important than the other.
• 🔲 Non-rectangular pixels, such as hex pixels, were used in early computer graphics for benefits like reduced aliasing and free transformations.
• 🎨 Raster graphics are graphics made up of a grid of pixels, with each pixel having a specific color, used in common formats like JPEG, PNG, and BMP.
• 🌐 The course will mainly deal with rendering, which is central to computer graphics, though other forms of graphics like vector graphics are not covered in this course.
• 🖼️ When zooming in on a raster graphic, like a leaf, it appears as a grid of square blocks, which is the essence of raster graphics.
• 📚 The script suggests that understanding the basics of raster graphics is important for grasping how images are displayed and manipulated in computer graphics.
• 📈 The course appears to be interactive, with the lecturer encouraging students to experiment with raster graphics to deepen their understanding.
• 🔄 The script mentions that while some modern programs may hide the pixel grid for a smoother appearance, it's crucial for learning to see the underlying structure.

Q & A

What is the main focus of the first lecture in COMP 3490 Computer Graphics?

The main focus of the first lecture is to introduce the fundamental problem of rendering in computer graphics, which is the process of converting abstract data into a visual display on a screen.

What is rendering in the context of computer graphics?

Rendering in computer graphics is the process of converting abstract data structures into a visual representation on a display screen.

What are pixels in the context of computer graphics?

Pixels are the smallest individually accessible display elements that can be read and written to, typically represented as squares on a screen.

What is an alternative to square pixels that is commonly used in certain displays?

An alternative to square pixels is anamorphic pixels, which are non-square and rectangular, often used in displays where one dimension is more important than the other, such as TVs.

Why might anamorphic pixels be used in video compression systems?

Anamorphic pixels are used in video compression systems to compress one direction more than the other, resulting in rectangular pixels, which can be beneficial for certain displays like TVs where one dimension is more important.

What is the issue that can occur if anamorphic pixels are not set up correctly during video conversion?

If anamorphic pixels are not set up correctly during video conversion, the image may appear squished or distorted due to incorrect pixel settings.

What are non-rectangular pixels, and why were they used in the past?

Non-rectangular pixels, such as hex pixels, are a type of pixel that is neither square nor rectangular. They were used in the past for certain specialized hardware and applications due to benefits like reduced aliasing and the ability to provide free transformations.

What is the advantage of hex pixels in terms of image transformations?

Hex pixels offer the advantage of providing five free transformations compared to the three that square pixels offer, which can be beneficial in systems where rotations are needed without losing data.

What is raster graphics, and how is it related to pixels?

Raster graphics is a type of graphic made up of a grid of pixels. Each pixel in the grid has a color, and shapes are created by coloring the pixels, similar to coloring on graph paper.

What are some common file formats that use raster graphics?

Common file formats that use raster graphics include JPEG, PNG, BMP, and PCX. These formats provide different features such as compression and lossless detail.

Why might some modern graphics programs not show the individual square blocks when zooming in on an image?

Some modern graphics programs may not show individual square blocks to provide a cleaner and more visually appealing representation, although this can make it harder to understand the underlying raster graphics structure.

Outlines

00:00

🎨 Introduction to Computer Graphics and Rendering

The first paragraph introduces the course COMP 3490: Computer Graphics. The lecturer mentions that the previous class was an introduction to the course and computer graphics, and there's nothing significant to remember from it. The focus of the current lecture is on the fundamentals of computer graphics, specifically rendering. Rendering is defined as the process of converting abstract data into a visual display on a screen. The lecturer emphasizes that rendering is a central theme throughout the course. The concept of pixels as the smallest individually accessible display elements is introduced, and the importance of their accessibility for reading and writing is highlighted. Pixels are typically square, but alternatives are mentioned, setting the stage for a deeper dive into rendering and pixel structures.

05:00

📐 Understanding Pixels and Raster Graphics

The second paragraph delves deeper into the concept of pixels, explaining that while they are predominantly square, there are alternatives such as anamorphic (rectangular) and non-rectangular pixels like hex pixels. Anamorphic pixels are used in certain displays where one dimension is more important than the other, such as in TV screens, and can be encountered in video encoding and old CRT displays. Hex pixels, which are less common, offer benefits like reduced aliasing and additional free transformations, which were particularly useful in early hardware and specialized applications. The paragraph also introduces raster graphics as images composed of a grid of pixels, each with a color value, allowing for the creation of shapes and images by manipulating these pixels. The concept is fundamental to various image formats like JPEG, PNG, BMP, and PCX, which are all variations of raster graphics, each with its own compression and detail preservation techniques.

10:02

🖼️ Exploring Raster Graphics and Image Formats

The third paragraph continues the discussion on raster graphics, providing examples of different image file formats such as JPEG, PNG, TIFF, and BMP, which are all based on the raster graphics format. It explains that JPEG uses a type of compression based on Fourier techniques, while BMP does not use compression, and PNG offers lossless compression, preserving all details. TIFF is mentioned as being more suited for cameras and printing. The lecturer suggests an exercise for students to zoom into an image using their favorite painting tool to observe the grid of pixels that make up the image, emphasizing the importance of understanding the underlying structure of raster graphics. The paragraph ends with a note on the lecturer's intention to continue the topic in the next part of the video.

Keywords

💡Rendering

Rendering in the context of computer graphics is the process of generating a two-dimensional image from a three-dimensional scene. It is a fundamental problem because it involves converting abstract data into a visual representation on a display screen. The video emphasizes rendering as a core concept, explaining that it transforms data structures like linked lists or trees into images that can be seen and understood by users.

💡Pixels

Pixels are the smallest individually accessible display elements that make up an image on a screen. They are the basic units of digital images and can be thought of as the building blocks for creating visuals on a digital display. In the video, pixels are highlighted as key to understanding how images are formed, with the script mentioning that they can be read and written to, and are predominantly square in shape.

💡Raster Graphics

Raster graphics, also known as bitmap images, are digital images that are composed of a grid of pixels. Each pixel in the grid has a specific color value, and together they form the complete image. The script introduces raster graphics as a simple yet essential concept in computer graphics, explaining that popular image formats like JPEG and PNG are variations of raster graphics.

💡Anamnorphic Pixels

Anamnorphic pixels refer to non-square, rectangular pixels that are used in certain display technologies where one dimension is more important than the other, such as in television screens. The video mentions anamorphic pixels as an alternative to the more common square pixels, explaining that they require additional mathematical conversion and are often used in video encoding and old CRT displays.

💡Hex Pixels

Hex pixels are a type of non-rectangular pixel arrangement that is shaped like hexagons. The script discusses hex pixels as an alternative to traditional square pixels, highlighting their benefits in reducing aliasing and providing additional free transformations. Hex pixels are mentioned as being used in specialized hardware and contexts like 3D printing and wearables.

💡Data Structures

Data structures are specialized formats for organizing, storing, and manipulating data. In the context of the video, data structures like linked lists or trees are used to store game maps or other graphical data that need to be rendered. The script uses data structures as an example of the abstract information that must be converted into a visual format through rendering.

💡Display Screen

The display screen is the output device where the rendered images are shown. It is the surface where the abstract data is transformed into a visual representation through rendering. The video script mentions the display screen as the final destination for the rendered images, emphasizing the importance of understanding how data is converted into something visible.

💡Image Formats

Image formats are standardized ways of encoding digital images. The video script mentions several formats such as JPEG, PNG, BMP, and TIFF, each with its own method of compression and use case. Understanding these formats is crucial for managing how images are stored and displayed, as they determine the quality and appearance of the rendered graphics.

💡Compression

Compression in the context of image formats refers to the method used to reduce the size of image files. The script explains that different formats use different types of compression, such as lossy (JPEG) which reduces file size at the cost of some image detail, and lossless (PNG) which retains all detail without compression. Understanding compression is important for balancing image quality and file size in computer graphics.

💡Aliasing

Aliasing is a visual artifact that occurs when an image is displayed at a resolution that is not capable of showing the fine details of the original. It often results in jagged edges or a stair-step appearance. The video script discusses aliasing in the context of hex pixels, explaining that their shape can help reduce aliasing by providing a softer edge compared to square pixels.

Highlights

Introduction to the course COMP 3490: Computer Graphics One.

Explanation of rendering as the fundamental problem in computer graphics, which is converting data to display.

The concept of pixels as the smallest individually accessible display elements.

Pixels are predominantly square in shape for simplicity in rendering.

Alternative pixel shapes include anamorphic (non-square, rectangular) pixels used in certain displays and video compression.

Older formats of non-rectangular pixels like hex pixels used in specialized hardware and early computer graphics.

Benefits of hex pixels include reduced aliasing and additional free transformations.

Raster graphics defined as images composed of a grid of pixels.

Different file formats like JPEG, PNG, BMP, and PCX are variations of raster graphics.

JPEG uses Fourier-type compression, while PNG is lossless and does not lose any detail.

TIFF is designed for professional cameras and printing, offering features for high-quality imaging.

Raster graphics are popular and used in common image formats like JPEG and PNG.

Demonstration of raster graphics by drawing a simple grid and coloring pixels to form shapes.

The importance of understanding the underlying grid of pixels in raster graphics for proper learning and application.

The video lecture will continue with more topics related to raster graphics and computer graphics in general.

Transcripts

hello welcome to the first

video recorded lecture of comp 3490

computer graphics one

all right so last class

we just did a quick introduction

so you didn't miss anything um there's

nothing to really remember

just an intro to the course

and an intro

to computer graphics

that's all we did so today we're really

going to get started with

the nitty gritty starting to learn the

first pieces starting to learn

the building blocks of computer graphics

that's today

all right so i'm going to start by

talking about rendering

uh rendering is a fundamental problem in

computer graphics

and you might have heard about people

talking about rendering before

it's not a big deal to understand it

it's simply the problem of going from

going from data to display it's from

data to display that's all that

rendering is

so you can imagine now that in your

program in memory

you have maybe a linked list of some

kind of data structure

maybe a tree whatever you have a game

map that you've stored

you've loaded in some images

right you have some points that you want

to render

so you have all this data but it's it's

pretty abstract

the rendering is simply the problem of

going from

that abstract data to something on your

display screen

that's it

and most of this course will be dealing

with rendering

in one form or or another

right so you have all this abstract data

and maybe when you run it on your screen

you get a nice

happy face right okay

i'm going to highlight these by the way

i'm really bad with being consistent

with my highlighting

so the colors don't really mean much

except for pay attention to them

so the first thing i want to talk about

when it comes to rendering are pixels

again you've probably heard about pixels

before but i want to talk about them a

little bit more

than you might have thought about them

before what are pixels

pixels are simply the smallest come on

there we go pixel's a smallest

individually

accessible

display elements

so this accessible is the key here you

can read and write them

right you can put them you can read them

and see what they look like

uh sorry give them a color and also see

what's already on the screen

predominantly these are

predominantly these are squares but i

will talk a little bit

about some alternatives so pixels are

generally squares predominantly

squares and there's no

real reason for this be except for the

fact that it's

for simplicity um maybe i'll jump over

to um

my slide real quick just to show what i

mean by this

so here's my that work i hope that works

um i don't think that works the way i

think it works

let me just change no presenter view

this i think that's right aha this is

what i wanted

all right so here's an example i have a

screen this is an old computer screen

commodore 64 something from the 80s

and you see this blocky font was very

common but if you zoom in

you see we have these square pixels in

this case they're on or off

off as black on is blue or it could be

white or green

and you take a letter like the a or the

r you look inside

and it's made up of these little square

blocks called pixels kind of like a

minecraft world

um so that's all that that pixels really

are

okay i can go back to my ipad so they're

predominantly squares

um there are alternatives i'll talk

about that but you won't really deal

with these

in this course but it's important to

know that alternatives exist

the most common alternative these days

we call

anamorphic

so we have anamorphic pixels now this

sounds really exciting anamorphic

they're going to come a lot no

nope all that anamorphic pixels mean

are non-square uh rectangular like this

and

we do this we do this because

on certain displays one dimension is

more important than the other

typically on a tv you have a lot of

pixels this way

and a few this way so you'll have

video compression systems that'll

actually have anamorphic pixels and

they'll compress one direction more than

the other your pixels become

rectangular instead of square you'll

come across this if you do video

encoding stuff

if you're with old crt displays you hear

about anamorphic pixels

all that it means is they're not square

they're rectangular

and you have to do some math to convert

them um you might have seen this if

you've done a video conversion and it

went wrong and the image looked squished

or squished you just had the wrong pixel

setting

but we won't really deal with anamorphic

pixels in this course

these are typically for dvd blu-ray

that world or tv

um yeah you can read up on this if

you're interested

but um don't spend too much time on it

there's also another

format and this is really dated now we

don't see much of this anymore

but you will see this in special use

cases and those are non-rectangular

pixels non-rectangular

so it's not square and they're not

rectangular what's left now let's let's

see if i can draw this

um one format that was pioneered in the

early days

were hex pixels and if any of you have

ever played

tile based for board games i'm going to

screw this up

there we go um you might be thinking oh

that's kind of neat

why on earth would people do hex pixels

there are actually a lot of benefits to

these kinds of hex pixels

one is aliasing we'll come back to this

later

but when you have square pixels that

line up perfectly

like this you end up getting a lot of

jagged edges

if a line's coming through like that

you'll get this pixel black

this pixel black and then maybe white

and white and you get a jagged edge

with these hex pixels you're more likely

to get a softer

edge the other cool thing about hex

pixels is you get some free

um rotations with our

square pixels i can rotate my image 90

degrees

180 or or 90 in the other direction

just by rearranging what way i draw it i

don't have to resample or recalculate

anything

with so i get i get three free

transformations with a square pixel

with the hex pixel i get five so in some

systems where

you wanted to do rotations um without

losing any data

especially in the old days hex pixels

were your go-to because you got these

free transformations

don't worry too much about it the reason

i'm explaining these to you

is that so you're familiar with the idea

and you might come across it i've seen

i've seen this hex pop up in some

printing contexts in some 3d printing

contexts

and in old hardware specialized hardware

like wearables

but you won't do that in this course

okay we're gonna stick to

our friendly neighborhood square pixels

okay but i wanted to talk about those

all right so these are pixels if we're

dealing with pixels we're dealing with

something called

raster graphics

raster graphics um

[Music]

is a really cool sounding word that's

actually really boring

a raster graphic is nothing more

than a graphic that's made up of a grid

of pixels

that's it it's a raster hey look i'm

drawing your your very first raster

yay okay so raster graphics

are just these grids if i have square

pixels my raster square but i could have

raster with

hex shape and or anamorphic or whatever

as well

so a raster graphics is just this you

have this grid of pixels and each pixel

has a color i have a green green green

you can imagine

um i could make a yellow pixel here i

could do whatever color i want

and you can make shapes by it's kind of

like coloring it on graph paper right

you can make shapes just by coloring the

pixels on your raster

raster graphics are perhaps right now

one of the most popular forms of

graphics in the world

if you've ever used a jpeg file

a png file

i figured what jpeg stands for

joint picture something group png is

portable network graphics

i won't get into the details of

different formats that's more of an

image processing course

but feel free to ask me if you're

curious uh tiff you might have come

across

old days you would have seen bitmaps

bmps

there's old pcx's blah blah blah all of

these

are variations on the raster graphics

format

jpeg uses fourier type compression

bmp is no compression png is lossless

compression doesn't lose any detail

this tiff is made more for cameras and

more for printing

they have all their features but the at

the bottom all that these formats do

is give you a grid of pixels okay

so i'm going to go back to my slides for

a second

um yeah so here we go right this is this

is a raster

raster graphics bam so grid you put

pixels in i'm also going to show this

one

and i'll come back to this again um a

little later

this is a raster graphic i have this

nice smooth looking leaf

if you zoom in it's just a grid in fact

i recommend you try doing that with your

paint your favorite paint tool you zoom

in you zoom in you zoom in

and you should see these square blocks

now these days

some of the programs try to be clever

and they don't show you the square

blocks anymore

they try to make them fuzzy make them

look really nice well

um that might look nice but it doesn't

help

it doesn't help us try to understand her

raster graphics work

okay let's go back

hold on maybe now's a good time to stop

and take a break

so i'll stop this video here and i'm

going to continue

um with this topic um let me come back