Mtg 2/23: Mon-09-Sep-2024

Outline for Today

Introduction

Administration

Response to Responses

  • How is the discretization of a continuous phenomenon achieved with regards to understanding the pixels of a display or an image?
    • Each pixel on a display of an image shows the value of a discrete sample of the continuous phenomenon
  • Do pixels have a specific size?
    • No
  • Can you provide a full course syllabus on UR Courses?
    • Yes
  • I had a hard time understanding some concepts
    • Please don’t hesitate to ask questions during the meeting (if you are comfortable with that), send me email using UR Courses, or post to the class discussion forum on UR Courses.
  • The concept of pixels being a continuous concept rather than a discrete concept. It seems to go against what I understood pixels to be before today.
    • Pixels are discrete samples of a continuous phenomenon
  • If a pixel can be any shape and size how do all screen appear to show non-stretched images?
    • Pixels as discrete samples of a continuous phenomenon do not have size nor shape. On modern screens, these samples are displayed equally spaced in x and y (resulting in a grid of squares). To avoid stretching an image, preserve the aspect ratio
  • I would like to know more about what is aliasing
    • Aliasing in computer graphics refers to jagged features apparent on what should be smooth lines and curves. It is a problem of insufficient sampling
  • It was mentioned that a part of our participation marks could be gained through wiki contribution. What is meant by this and how do we contribute to the wiki?
    • I’ve added some information in UR Courses (under the Participation topic). It is not strictly necessary to sign up to edit the wiki, you can just do it (see Using Wiki for an introduction to wiki editing
  • How can we get to volunteer to participate in research through the participant pool?
    • Opportunities to participate in research will be advertised on UR Courses
  • Would it be possible to get the course lecture slides?
    • Yes. I am adding the textbook slides in a folder under the Meetings topic in UR Courses. The meeting pages will have other information covered during our class meetings

Today

For Next Meeting

Wiki

Link to the UR Courses wiki page for this meeting

Media

Transcript

Audio Transcript

  • How's that for? Is that helping?
  • What about now? What if I talk right into it?
  • Let's See if that helps.
  • How about this better? Does this sound better? Okay, we'll try
  • that. Let me know if you have problems hearing Me.
  • I Okay, so this is on my laptop. I was going to publish it to my
  • website before class, but then I realized I needed to do
  • something else. It was going to make me late for class, so I'm
  • going to do it right afterwards, and you'll be able To see this
  • on my public website. You Thank
  • you. How's everyone doing today? Good, first Monday of the
  • semester.
  • Anyone like Mondays? No, usually we have two meetings a week,
  • classes go, Tuesday, Thursday. So this is a bit of a change of
  • pace.
  • How does that look better size? Okay, so we started yesterday by
  • going over the class structure, and we started a discussion of
  • computer graphics.
  • So I just wanted to show you what we'll get. So here's a link
  • to the wiki,
  • and so I've added in your courses scheduled for wiki
  • editors. So I didn't describe this very well, or I didn't
  • describe it at all the other day, this is a place where and
  • we can still so you can still put your name down for
  • yesterday's Meet, last meeting, because
  • it's just a matter of
  • we can still go through the records that were created that
  • are on the page. I
  • it. So that's just a way. That's a way to participate in class,
  • if you'd like to do that, get some of those 4% marks for that.
  • Another way to do that is to attend classes and participate
  • in class discussions.
  • So my thought for the wiki is that you'll take the media
  • through the photos of the board. There are nine of them here.
  • Anyway go through there, and then there's also
  • transcript of my recording of the meeting, and I'm recording
  • that now, so I'll have the pictures and the recording done
  • and posted online later today.
  • So the transcript may be helpful, but
  • some words are not well transcribed. You
  • so I included a bit of discussion after class.
  • I So then here I've got the responses from last day. I i
  • would say a wiki someone might put I'd invite you to do some
  • editing of those things that have put together a highlights
  • package, so to speak. If you want to do that,
  • get the key points of our of our meetings, and possible some rep
  • possibly some references to new material, or that would support
  • our discussion. Does that make sense? Do
  • so I've tried this in the past, and it hasn't taken off, but
  • maybe making it more front and center this year this semester,
  • will help.
  • Anyway, so there's that. So this is there'll be page like This
  • for everything, every meeting we have, I
  • those attendance in your courses, you can do that for
  • yourselves. If the class calendar for today, I
  • now I'm wondering, Where does go back? So upcoming events should
  • show the quiz as well. I
  • so from 6pm tomorrow until the start of class on Wednesday, the
  • quiz will be available. So what'd you think of the setup so
  • far? And we had some you. A reasonably good participation. I
  • guess.
  • Any thoughts on that? Yeah, I think the
  • quiz room for class and response after class model, the the epi
  • class from last year. I don't hope that quite fits the middle
  • currently graphics, so I find it kind of difficult to clear what
  • service so on to after like a given thing for like, something
  • where it's really technical, whereas with that it's more like
  • open ended, like we had to go Quandt, like big tech and like
  • data harvesting from last year was, like, something's really
  • big, but I don't know If it quite works as well for this
  • class. So as well for this class,
  • okay? Well, the idea is it's not necessarily big ideas or small
  • or small ideas or technical issues. It's just to keep the
  • it's a way to in the way I see it as a way to for you to give
  • feedback. If there are questions you're having problems with,
  • hard to explain, you still have questions about it after a
  • discussion, then we'll take it up the next day. So maybe,
  • maybe it's not asking for a philosophical answer about what
  • are the important concepts? So maybe you could focus on the
  • things that get causing difficulty, or the things you'd
  • like to know more about. Maybe the lizard.
  • So I appreciate your comment, and we'll see how it goes. But
  • it's going to be still a way for you to get
  • some rewarded for your engagement in our ongoing
  • discussion this semester. Does that make sense? I
  • Okay, so I opened the can of worms by Asking about pixels and
  • 1000 of that in Georgia.
  • So we talked about pixels that need samples last day, so I want
  • to focus on the fact that we don't have geometry associated
  • with the pixel. So
  • I wonder that wasn't a very good way to start the class, perhaps
  • talk about things that might be difficult to Understand, but
  • we'll
  • talk a Little bit more today. I
  • so Just a quick look at the response, my responses, your
  • responses from last day. So I wanted to say everyone who
  • submitted a response received full marks, although I did see a
  • few nos, meaning the instructions weren't followed.
  • So I'm wondering if that's Maybe not a thoughtful response. So
  • so I'll get the PDF of the syllabus online today, later
  • today, I've just had a few technical issues.
  • So who's got the textbook sorted already. So I've had a
  • discussion with the text with the bookstore on the campus
  • store, and I asked them about this. So here's a query for the
  • course materials.
  • So I asked them about this, because I go To the publisher's
  • website. I
  • so
  • I would invite you to talk to the campus store about this
  • discrepancy, Because the manager knows about The difference in
  • price. I
  • So we want to talk about the textbook issue.
  • Are there other alternatives to get the eighth edition that are
  • better still than two that I have? I i
  • guess I'm thinking about unconsciously writing smaller
  • ears so I don't have to go over the this. Because this this
  • board is fairly clean, but the other ones are already have A
  • good portion of chalk dust on them. Anyway, I
  • so just say earlier editions may be helpful if you if you have a
  • copy of the
  • can you say what's being passed around? I don't
  • know. It's like a job or opportunity then,
  • Oh, okay. Thank
  • so literally, additions may be helpful the
  • website for the text and
  • is there? Interact computer graphics.com, so you can see the
  • source code and other details. I
  • pixels ensemble and
  • I should Have a chalk sharpener. I think that would help that
  • like they exist. Are you laughing with me or at me? Okay,
  • yeah, so anyway, I'm not doing well with writing magically
  • today. How many samples do we need to reconstruct a continuous
  • phenomenon?
  • Any thoughts about that theoretically,
  • the more the better the
  • so we're so it depends on about the resolution of our the
  • capability of our sampling device See how much, how close
  • we can Get to infinite.
  • So to go back to my sifter or strainer analogy from last day,
  • how what size mesh do we need? Or what is the size of the mesh
  • we're Using? How does that determine what we can
  • reconstruct the
  • smaller than a mesh and
  • okay
  • to know what's happening for CD audios, audio Compact Discs. How
  • many people know about audio compact discs
  • used to be that actually own several audio discs, but maybe I
  • don't think they're very popular item these days, although vinyl
  • is making a comeback, So my turntable is as Life again once
  • more. I
  • so the audio, CD, format sampling at 44 kilohertz and
  • so what can you hear? 44 exams. So people with good hearing,
  • young people with good hearing. May they want to know offhand
  • with the answers, what's the highest frequency people can
  • hear you?
  • So what's the so not everybody has compared to 22 kiloHertz,
  • that's a common so the one I
  • so can sample 44 kilohertz, And we can reconstruct sounds of the
  • 22 kiloHertz i
  • Let's turn it again. So if we're Dealing with graphics, I
  • so for graphics from the sample of twice the resolution of the
  • smallest feature we want to capture.
  • So the mesh should be half as big as the
  • thing we want to capture, the smallest thing we want to
  • capture. Does that make sense? I
  • behind that are Nyquist And Shannon i
  • So I
  • so pixels of samples of a continuous phenomenon don't have
  • shape and just the value. So I want to take a sample of this
  • classroom.
  • We which should i What would be the most representative sample?
  • Maybe the color of the chairs, maybe the
  • wood paneling or the desktops, or thinking
  • about being one, but this is zoom down. The way these you may
  • only have one pixel. So you might only have one pixel to use
  • for this, say for looking
  • from the drone or further out
  • in space, not
  • feeling
  • I feel like for every region of space that we're sounding, we
  • need To decide on the value associated with that sound.
  • So then that value we choose To represent the sample gets so
  • so the samples on display their range, so that they're
  • equidistant. So it's going to be written with squares. So pixel,
  • according
  • at that grid position, displays the value of the sound. So we're
  • going to talk about this more in detail. So
  • so arch is red, green, blue. We'll talk about that in the
  • coming weeks as well, how we can depict color, store color in the
  • images that we work with. So
  • so I wanted to talk a little bit of it, since we broached the
  • subject, a bit about vector graphics, let's talk about that
  • as Well. I
  • So there bit about displays, like on your my laptop and your
  • laptop and so on, they have a resolution So that and those
  • pixels are addressable, and we get so we make an image by if we
  • take a picture of this classroom, let's say, this
  • continuous phenomenon. Then we decide which the size of the
  • image we're making. That we choose the value for each of
  • those samples you
  • so the screens on devices are discrete. Do we have any did
  • anyone have any experience with continuous output devices.
  • Yeah,
  • yes.
  • So, my knowledge of oscilloscopes is limited, but so
  • there are I
  • so another One that I'm thinking of is a modern it's has anyone
  • worked with the plotter before?
  • So that is has a large sheet of paper and a set of pens, and you
  • can direct the pens to go and trace out shapes and so forth.
  • Maybe it's similar to a CNC machine.
  • Is that? Is that a more current reference? I
  • so the idea is we're not we're not limited by the excellent
  • addresses. We're we have a 256 by 256 image and
  • so we're constraining the element to the coordinates we
  • have in the image, but in a plotter or an oscilloscope, we
  • don't have addressable units that we're not lock step
  • required.
  • So that allows us to get more fluid, fluid imagery without
  • charging interest you.
  • So Anyone familiar with the cathode ray tube? I
  • so We can produce drawings as we stimulate the phosphorus from
  • the back of The screen
  • that where the electron beam hits will Be we'll light up the
  • screen at that position we're
  • so you do the same. You
  • so we can have continuous shapes if we don't have any
  • restrictions on how the beam can move.
  • So the downside is the phosphor will only stay, will only
  • continue to admit emit late for a period of time. So we have to
  • go back and refresh The image if we want to. We
  • complexity and
  • effect. So alternatively, Here's how
  • Okay, shadow mask, which only allows the electron Beam to hit
  • at certain spots. So this is development with TV.
  • You scan. We're not
  • having to lean on continuously to make a shape On the spray
  • when we scan through the lines and
  • so early TVs divided the image into the frame so they would do
  • the odd lines At once, and then the even lines at a certain
  • time. So you could, we still have a problem of refresh, but
  • the complexity of the graphics can be more advanced because
  • we're decided we're assigning them to positions on the on the
  • display you
  • so you may have heard the word roster before Anyone heard the
  • word roster before. So that just talks about how you scan from
  • top to bottom.
  • Okay, so let's say our modern displays are dealing with
  • bitmaps. So the question is, well, how do how do we deal with
  • vector graphics, where we are drawing shapes without without
  • directly being discretized. Does that Question make sense? I
  • Okay, So I
  • so let's Say we have a square filled with right to a grid,
  • five by five, and at this resolution we can draw, let's
  • Say we can draw a
  • so let's say we have a resolution that where this shape
  • that we've drawn is of acceptable quality, but if we
  • zoom in or make that, there's no more data in that image. So if
  • we make it larger or zoom in, I
  • it. So if we store it into Bitmap, then we're decided which
  • what the resolution you want to store it within.
  • And so once we have a bitmap, we're limited to the display
  • size that we can. We
  • can the size of display is limited by the precision of the
  • graphic that we've created that we stored In bitmap form,
  • if we Have a vector image.
  • So this would be a higher resolution than say,
  • I'm not going to draw it. Says I'm not going to draw it. What
  • kind of resolution would you like to see? I
  • 256 by 256
  • so we have a description of the shape I'm going to draw, and
  • we reevaluate The formulas or the mathematical description of
  • the shape for the screen resolution that we have. Does
  • that make sense? I
  • for the little graphic on the science, it's maybe a clear
  • explanation so we can so SVG, format, Scalable Vector Graphics
  • that's stores the mathematical description of the shapes of the
  • elements of the image. And so based on the resolution that we
  • choose, we're not stuck with a very low resolution type Path,
  • and we need to redo or work with native
  • a poor approximation to the so you can see, when you zoom in on
  • the raster image, we get artifacts of the
  • discretization and a lower reservation, and we zoom in on
  • the vector graphics in SVG, for example,
  • we can recompute the discretization at the resolution
  • we have so We always have smooth graphics. Does that make sense?
  • I
  • so if we have a vector graphics image, it'll take more time to
  • render it, because we have to compute the new bitmap at the
  • current resolution and so, and also save space, because
  • generally the mathematical description will be less storage
  • consuming than then the set of pixel samples, pixel values for
  • the image. So bitmaps, once they're done, they're easier to
  • they're quicker to render, but they take up more space. So
  • there's a trade off between those two kinds of graphics and
  • so have I cleaned up issues that I created on questions that I
  • created on Monday or Wednesday last week?
  • They see a bit more, little better contextualized now
  • and I'm not going to
  • go another day without getting this website sorted out, both on
  • your courses and on my own site, so you can look forward to
  • seeing Some posts from me today for that i want i
  • I just I had the Text open Somewhere here i
  • So I invite you to look at chapter one for Wednesday. I
  • think I recognize this from it's part of the visible healing
  • project,
  • speaking about ethics. So this was, I believe, prior my memory
  • serves. This was a person who is in prison who decided that upon
  • his death, he would be frozen and cut into slices and scanned.
  • So this is why we have exceptionally high resolution
  • images of people of a person now,
  • anyway, I just seem to since we're talking about ethics,
  • ethics is never far from any discussion that we have, I
  • think. But we're going to have a computer graphics this semester.
  • Okay, any questions or concerns before I let you go? You
  • okay. Thank you for today, see you on Wednesday

Responses

What important concept or perspective did you encounter today?

  • An important concept from last meeting that was brought up was the difference between vector and bitmap graphics.
  • Audio sample rates
  • I started to get a grasp of raster and vecotr graphic types and how their differences affect the final product along with how they are affected by different resolution types.
  • We discussed the differences between bitmapping and vector graphics and how both have advantages and disadvantages. Much like data structures and algorithms, there is never a one size fits all solution to problems in computer science. It's up to the designer to choose what tool is best for a given problem.
  • The intoduction to a method of anti-aliasing known as Super-Sampling (SSAA), which can greatly improve image quality, however the method of rendering at a higher resolution does put into question the affect on performance.
  • intro to vector graphics
  • pixels and framebuffer
  • Nature of pixels
  • I loved the concept of vector graphics.Though I didn't get it very well.
  • We looked at the concept of bitmap and vector graphics, which are discrete and continuous respectively.
  • We encountered about pixels and vector graphics
  • Bitmaps v/s Vector Graphics. Cathode Ray Tube. Pixels and Sampling. Audio CD's
  • There are two types of computer graphics - vector graphics and bitmap graphics. Vector graphics can give us a clearer image, but they are too slow when compared to bitmapping/raster, which is used for most modern devices
  • Today, I encountered several important concepts. Pixels are samples of continuous phenomena and don’t have shapes. I learned about display technology, distinguishing between discrete screens and continuous output devices like oscilloscopes and plotters. The professor explained how drawings are produced on Cathode Ray Tubes. Another interesting concept is that vector graphics use mathematical calculations to maintain image quality when zoomed in, saving space but potentially taking longer to render.
  • We learned about vector graphics versus bitmaps. It was cool to see how vector graphics use math to describe shapes, letting them scale without like losing quality.

Was there anything today that was difficult to understand?

    Was there anything today about which you would like to know more?

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