Mtg 14/25: Wed-25-Oct-2023

Outline for Today

Wiki

Link to the UR Courses wiki page for this meeting

Media

Transcript

Audio Transcript

may not be winter yet. The snow may still go away anyone excited
to see the snow
So I'm using something called grade scope to do marking up
exams. So I'm going to scan your exam papers, put them into the
system then it just helps manage marking. And then at the end
you'll get an email with your graded copy and comments that
you can read because we'll be typed in instead of me instead
of trying to decide what I've scribbled on the paper on the
board
any thoughts about the midterm was a reasonably fair assessment
of learning.
So I know you're not going to tell me otherwise when I'm
asking you to your face but I wanted to let you know that you
could be free to do that.
Turn that off.
So the feedback and I'll give you all the responses from the
feedback I'll post them and you'll be able to see all the
responses.
So common a few times and sometimes it came up in the
strength so I'm not sure if if I should have efficient
interpreted as a strength or still it's an issue anyway.
So I do have a list of slides on New York horses
and there's also
slides on the interactive computer graphics.com website
So maybe I'll add this as a link to my course web page so it's
more clear as well where to find these things.
This seems to me to be a bit of a mess. Anyway.
Anyway, I'll track down
so I'm really feeling old today because my back is sore. I don't
know what I did. So I'm trying. I'm trying to not look like an
old man.
can let me know if I'm succeeding. Or not.
So there's a common about putting audio with not just the
AI generated transcripts but your audio recordings. I think
that would be a hell.
I think it's better than the transcript. Because it's like,
separated in middle of sentences. Yeah, hard to
understand. I think I'll do it okay.
So it's not on the public website, but it'll be on our you
our courses. Page.
So I wonder if it might be a useful thing. For so we have the
raw transcript but then also if I create an edited version to
transcript Yeah.
Okay So
How to Make it Monday
is it possible that more two days like first of November
events okay Thank you
End of class we see kind of the last ones end of last meeting.
So Mr.
We could do it a couple of days after the end of the semester.
Or upper class meeting.
Something to think about I can discuss this on on the forums.
In your courses.
Right Sophie?
Have you looked at the description of assignment to Z
expectations are the expectations more clear
I think Yeah.
Comparison to the first one yes. Thank you
Okay in comparison to the first one that doesn't say better No,
it is
okay, so it's maybe better but it's not.
Let's look at it and see if we can improve it.
Okay so right to left jail programs, HTML and JavaScript
proven add functionality in the code from attacks
so square m is one of them.
So the two things I notice about this program
Shut up open a new window. Let's go back.
So allow for selection of colors allow for input positions to be
overwritten. So the storage is not exhausted so
the points don't just disappear at one point there. And then so
if
if we're doing some other structures on the page so that
the canvas isn't at at the origin at the top left of the
mouse position stuff will still work. So one of the other
examples I did in class is in the code directory handles that
so you can use that as an example.
So it's perfectly fine to use other code in your solutions,
just make sure that you're you indicate that you're getting it
from somewhere else. Okay,
Again,
so with these it is to combine them and select attorney and
toggle between them with a button on the interface
and just give a bit more feedback and what's going on
that's intent for that part so.
So I have graphics implementation interaction,
implementation, and comments.
For each of those few programs I'm asking you to write
how does that seem anything that any questions that jump out?
Think it's better if I keep moving. Less. Pardon me?
You said it's better to keep moving as fast as it hurt less
to your back.
Yeah, let's just it's getting up and getting started that that
are the problems
okay.
All right so we'll leave it there.
Do you have something to share? My boss
Okay.
So the next chapter is lighting and shading in chapter five, as
a program about shot doing shadows, but the shadow requires
a light so I thought you can have a bit of discussion about
lighting and shading and then next day we'll go back to the
shadow and then some other application some other sample
programs in chapter six. I'm making sure that you know I
don't get
Okay so this
cube that we have there.
So how to describe the cubes so that one and other ones we've
encountered
so how would you describe the colors and shading?
MR is the class participation part.
I have a question about shading with me say shading in like in
terms of like painting and all of that you would like to shadow
to the cops. But in terms of computer graphics what is
failing
it's safely during the shadows since
we're computing we have a model of the interaction of the Elvis
in the scene ultimately will give us a more nuanced
representation seems more photorealistic or lifelike so so
yes, we're adding details that make it appear in this more more
believably in the scene and shadows and highlights as well.
So we can say this is what we see on our screen. On the cubes
today, we're just seeing flat shading so we're not we're
assigning a color without any other computation involved. So
we don't always have solid colors sometimes if we've
assigned colors to different vertices, different colors,
different vertices then we see those colors get interpolated.
But they're still
we're still using a flat shading approach. We're not getting
other information there. too.
So what information is missing so that we could have that will
allow us to create richer scenes
so we can see. anymore? You are
see reflections in
desks and also a little bit chars?
I apologize my writing is getting smaller like sort of
lighting, so position and types of lights so you can think of a
point like
if we have a bald let's say that's going to lay it up in all
in the
every direction from that ball will get some light so it has a
position and has yes so we can have a point light. We might
have a directional light that seem it's like the sun is
coming. Sunlight is coming from a certain angle and a certain
cut time of day.
So those are two important kinds of legs you can use
and if you want to think about if his services are very shiny
these ones where maybe if we have some, like the doorknob is
quite shiny so we want to describe the properties of the
material material
okay. So
I can do better than that?
Started out okay
So we can calculate interaction with the light
So one approach is to
so we can do the calculation and the vertices within with the
normal vectors. So we can get the
so we get values for the vertices and then we can
interpolate them.
During the calculation of the vertices and then interpolating
to interior points on the surface that's called Girl
shading
so, one thing about the interaction here was
light and normal vectors so, what if we have a light here?
Let's see intuition about that
so what if this is a normal this is a lightning vector
is that circumstance service is going to be led by the light
that's like habit that's like being lit by the noonday sun
right when the normal and later a line like that what if we have
a situation
this is and?
This light is just above just less than 90 degree angle with
the normal vector that's maybe like sunrise or sunset and then
so what happens if we have an oral vector?
So it's not I know everything looks like 3d. Imagine us 2d. So
just looking at the angle between the normal and the
laning vector. If it's greater than 90 This is a surface being
led by the light.
This is the surface or surface and this is in the truck as the
lighting so we go from here where the lighting the lighting
vectors aligned with the normal vector that's clearly going to
be led by the light and then if it's just above, just less than
90 degrees we're getting some late in the surface
and then if you have greater than 90 degrees design isn't
going to contribute to the color of the surface. Okay that makes
sense.
So in order to get shiny highlights
then other than just say Another approach is to
interpolate the normal vectors
whereas here we did interpolating values are going
to interpolate vectors
the interaction I'm doing terrible again the size of the
raining I apologize.
So we're not just interpreting values we're calculating colors
and so we're doing this calculation the length width at
the intermediate points along the surface
so because we're doing a calculation of vertices here we
can do this in the vertex shader. The following shading
which requires
not just the vertex information but so this is what we're doing
a fragment shader
I can understand it's like calculate interaction of light
at unlimited points
of intermediate
any other words that are
President wants to retain the large shake which kind of
pH O N G funk shading?
Sure,
the question What about intention of intention
or interaction and the surface normal factor
surface normal bacteria is a vector perpendicular to the
surface. So, remember we talked about the advantage of using
triangles as opposed to quadrilaterals because
quadrilaterals might not be in the same. They all might not all
the points might not be coplanar. So, if we stick with
triangles then then we can get the normal from the triangle on
the surface
makes sense. So we can do a cross product
How's that for a diagram let's try it again.
So we can get nursing effects and more complicated server more
interesting looks that we'll talk about later on in the
semester by perturbing the normal vector, so we can pretend
that the normal vector is is different than it is for just
the triangle. will pretend that we can use we can change it from
the triangles normal vector to something else so that we can
get a surface that looks more interesting. Anyway think about
a time for today
so, have a look at chapter six and suddenly code there and
we'll come back to our shadows and other examples from chapter
six. On Monday okay.
So on my Mac I have it set up to like in zoom when the font is
too small, so it'd be nice if I had that capability for you on
good zoom into my microscopic writing sometimes because it
wouldn't be bad if it just microscopic. Microscopic
scribbles are the real problem. Anyway, I'll keep working on it.
Anyway, thanks for your attention today. Have a good day
and we'll see you on Monday. And I'll be around tomorrow for
office hours. If you need to get in touch with me.
Okay Thanks
Thanks, you too.
Sure. Mom marks
Okay, so there any problem with the program?
Just a second.
Just a second.

Responses

What important concept or perspective did you encounter today?

The most important thing I discussed was the importance of lightening and shading ing in computer graphics.How the normal vectors and normal vectors can be interpolation.
Today's lecture was really interactive. it was super productive for me. Also, the deadline for the assignment got postponed today.

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

Today I have learnt that there are 2 lighting (point and directional) to rich the scene. I also would like to know more about 'Spot' light that’s located at a point in the scene and emits light in a cone shape.

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