Mtg 16/25: Wed-01-Nov-2023

Outline for Today

Wiki

Link to the UR Courses wiki page for this meeting

Media

Transcript

Audio Transcript

• Okay, we're still a little bit we're not quite on time yet. So
• morning.
• Yes
• question the assigned today is the last day of submission,
• right?
• Yes and one minute to midnight tonight.
• Is there any flexibility on that I have a root canal treatment
• today oh and I don't know how good or bad that's gonna be. Are
• you going to Doctor fee? No. Campus? Dentist yeah what do you
• mean by a decision people get every page I had already it's a
• root canal
• yeah I've had to
• this the first time
• I've never had
• my dentist. So the thing is my dentist said oh, I can do this.
• And he did it but he couldn't get all the routes out. So then
• I went to see an endodontist who's in southeast Regina. Dr.
• fee.
• So anyway, are they good?
• Yeah, they're good. But I mean, this one tooth boy has bothered
• me for 50 years. So there's a time where I've just putting it
• off and then I finally got a root canal and then a word was
• better for a while but then I got infected. Anyway so if you
• have the chance. Me some places have entered artists who do the
• root canals and things like that
• for two hours, blocked out two hours had they actually so he's
• so I've never had any dental issues back home. So I'm from
• India and never had any dental issues. I land here four days
• later, I get a toothache and then my insurance doesn't cover
• dental because I just landed and it activates in September so I
• was living with toothache. for like eight, nine months. And
• then when I went there, he's like, Well, you waited a little
• too long. So I'll try and RCT but come ready for an extraction
• that's not something that I was looking forward to.
• Well, we're not talking it's now 10 o'clock we could start no
• more talking about root canals. I was gonna say that once. I
• used to go to a computer graphics conferences. Like
• SIGGRAPH, the big one in LA and is mostly in LA now it's been in
• Vancouver and other places as well but it was in LA
• and obviously, in these things called Invisalign, or
• I have those.
• So
• they were recruited ever recruiting at SIGGRAPH for
• people to do the
• graphics with models of the teeth I got cells from scans. So
• I remember I remembered that for some reason, because I didn't
• have Invisalign when I was had my braces. I just had braces in
• high school which were which were not fun
• so sorry. Back to where we started. Would it be possible to
• extend all right, right. And not just for me, I don't want
• everyone else today. So could it be possible to extend it for the
• whole class by another day?
• Or we can say two days. How's that?
• Sounds great. That's a Halloween.
• Today is All Saints Day, all things all things Halloween is
• the Eve the eve of All Saints Day.
• It's written Hello. The E apostrophe en at the end is a
• contraction of
• evening Eve anyway.
• Okay, so let me
• log into your courses and change that right away. So then Monday
• we'll have a discussion about next assignments. Sounds good.
• So we'll fit three of them in somehow over the next or the
• remaining part of the semester.
• So while I'm doing this you can all take record your attendance
• Don't forget about doing the responses to meetings. I've
• gotten a bit out of my rhythm here but I'll get caught up.
• I should turn this back on or put this on the screen so you
• can tell them I'm not just making it up and changing this
• for you.
• Okay,
• so is there a reason do you think that I only have five
• to 13 people here
• Professor something brought up that I've lost. People are just
• not getting good with the weather. Like with the sudden
• change a few of them felt sick. I
• was sick I guess it was wondering too. About whether
• it's if you're living in different parts of the city it's
• hard to come to campus or
• anyway try and
• make the class time valuable
• especially today, you can tell
• put a note on our courses they should come or
• come to see me in my office
• so here's proof that I changed the date. It's not on yet
• okay, so
• you see that the new date for assignment two Thank you
• hello morning.
• To be able to
• communicate across the coffee or people suddenly have an
• extended.
• Practice
• save me shave
• Okay, so the two of you came in. Here's the reward. Thank you so
• much. Thank you one candy bar goes down.
• Okay.
• I'm feeling like I'm writing my writing is reasonable size here.
• He just can't get the lower right he gets smaller. So maybe
• I'll just read on the top of the board just one line one line.
• Next line Yeah.
• So I've improved that
• that cube example and we'll look at that in more detail
• what are some of the ideas
• that you
• that you had that you've
• gotten from the past or previous discussion about lighting and
• shading
• we had the local light coming into view
• so we can have
• that's fine
• so here we sit down to get comfortable
• my wife pointed out today some of them are peanuts in them.
• Yeah this one Yeah. Peanut Butter anyway but you're welcome
• would surely pointed that out after she was there when I
• bought them and I said I was gonna do get one of each of
• these two boxes from Costco
• and, and then yesterday, it's like, well, why'd you do this?
• But you're right I don't know what I was thinking. Anyway. So
• I hope there's no one allergic to peanuts
• anyway, so
• I'm talking about point lights or point light is located in the
• scene in the world coordinates. And directional light is you can
• think of it as being off an infinity let's say the sun so
• you have a constant angle of the light direction for directional
• lights, but the angle of incidence of the light from a
• point light is going to change depending on the orientation.
• Pardon me.
• So we talked about the difference between calculating
• intensities of vertices or calculating colors of vertices
• and then interpolating that along the edges compared to
• calculating vectors and interpolating vectors so that we
• can do lighting calculations as appropriate at each point along
• the line as it gets transformed.
• So if you want to do
• calculations based on vectors between vertices, what do we
• have to do? In general terms
• where do we have to put the code?
• Could you repeat the question?
• If we want, we don't want to just interpolate colors between
• vertices but we want to interpolate more information to
• get a more realistic sense of highlights on the surface for
• example. Where do we need to do that calculation? In the
• shadows,
• yeah, okay,
• they're in the shaders. Yeah. So in our JavaScript program, we're
• organizing the data, then passing it to the shaders, so
• the shaders are. So we're doing for each vertex we're getting
• recalling the vertex shader. But then, for each pixel, we call
• the fragment shader.
• So if we put.
• Following Fung Shui so where's my cut off here? Here,
• yep, that's it. Okay.
• All right. So I'm gonna try and stick with that. We decided that
• I'm doing fine writing at the top of the board. The writing
• gets smaller as you go down the board. So we're going to try and
• manage to keep
• writing the top
• so I want to just make clear that there's two different parts
• to
• this entire board flying so there's shading and reflections.
• So there's a modification to the farm reflection. model called
• the blin farm fun model. That
• so instead
• of having to look at the interaction of so doing the
• calculation based on the labor position vector and the viewer
• we can approximate it using a normal
• which means we don't have to do that calculation in the fragment
• shader. We can do it in the vertex shader.
• So let me show you what I did to the
• shaded q1
• Okay, so here we are
• so I put the latest
• API point. Let's do some rotation here.
• So you can see they did a once the face is facing us. It gets a
• highlight.
• That makes sense.
• Yep.
• Okay. Let's look at
• this, while it was rotating, even on a axis which should not
• be directly pointing at me there was a highlight. So if you
• rotate it now. So even though it should not be because it is
• turned on an X, Y and Zed x one three of them, so no face should
• be directly looking at. Actually, that if you had this
• one, so this highlights is the reflection still accurate.
• So let's look at
• the card game
• meant.
• To be about
• Okay.
• Course the sharing is good.
• Morning Okay, so
• what we're doing in the vertex shader here. So first
• transforming the vertex into my coordinates. So we're specifying
• the view position and the leg position in world coordinates.
• So we use the model view matrix to get the new position of the
• vertex in world coordinates in our model viewport and that's it
• so
• they're like factor is between like position and the vertex
• and as a viewer position, so I've added a variable to
• indicate that in the JavaScript program so this halfway vector
• we normalize the length vector because of your vector
• and then we get the normal vector from the vertex
• which we chain
• put into world coordinates coordinates and then we compute
• the different terms
• so we have an ambient, diffuse so that's the main contribution
• that's the main lighting contribution. We see when we
• have a light is a diffuse reflection.
• So k d is based on ganglion between the light and the
• surface normal.
• We're multiplying that by the product that we're getting from
• our program
• and then the specular highlights we're looking at the angle
• between the normal and the halfway vector and erasing
• the power of shininess to get the constant that we're modeling
• so if we don't
• to zero raise the bar of shyness is not going to give us any
• highlights so we only see highlights when we're facing the
• light which is about the viewer position.
• Material is defined in this as well so like reflective
• materials as opposed to
• so the material properties are defined in the program, the
• JavaScript side, okay. And so that's encoded in three years.
• In these products. So look at that next.
• So we're having
• a defining some storage here near the vertices. So we're
• doing a cube centered at the origin minus point five minus
• point five minus point 5.5 point 5.5. So it's a unit cube
• centered at the origin so I've added viewer position in the, on
• the website as a position for the viewer, but it's not used.
• So I made use of it here. And here's the leg position. And
• I've set the leg position to be the same as same as if you were
• a physician. So you could change that. So the length for the
• ambient is a low powered light, but it's a white light because
• we have
• light
• intensity, same intensity for red, green and blue. And then,
• here we have a few sliders, full intensity white specks, their
• latest full intensity white as well. So here are the materials
• for the ambient, so this is
• blueish and this is red plus green. So it's yellowish and
• this is white ish.
• And we put material shyness at 100.
• Sooner during the cube we do the faces. So we're doing a
• quadrilateral but then we're dividing those into two
• triangles and we're taking
• finding
• finding the normals based on the subtraction so taking two
• vertices so we get a vector and another vector and then we do a
• cross product to get the normals then we're storing the vertices
• and the normal vectors. So because the quadrilateral faces
• playing here, so we can just store with the same normal for
• each vertex
• so here we're creating a normal buffer buffer for the normals.
• And we're storing that data in there. And we're making a
• connection between the attribute normal in the shader with our
• their data are doing the same with the vertices so we have a
• projection matrix which does
• the graphic projection so a parallel projection and then the
• ambient product. So we're multiplying the light times the
• material ambient properties so that's where the information
• about the surface gets fed into the shader. Because then we're
• going to make uniform
• so you Ambien product, so that's the place in the shader. We
• connected with the variables in our jabsco program the render
• we're doing
• multiplying the modelview matrix, start with identity
• matrix, and we multiply by the rotation in x, y and Zed
• and then we pass that to the you ModelView matrix in the shader.
• So that's how we transform the vertices. into real coordinates.
• Tertiary move the light to what change would you like to make?
• leg position or the actually let's try it let's do
• another version of nmbm Lake which is.
• So he's a full intensity. Like for the Ambien chaining
• Save?
• So we made
• the ambient faces blue. So you can see that we're getting lots
• of blue
• and then because surfaces Wait
• let's make another
• change. Here.
• That's that's a big impact
• go back to our original ambient light
• let's see what if we move too late to a distance of two
• so light position vector this is the value of the distance of the
• light or the angle of this is the
• position of the light. Right so and so when I do the calculation
• and shader comes true. So we're transforming the vertex. So the
• position the pause vector has the role coordinate position of
• the vertex. Okay. And then the lake position is there and then
• we're going to normalize this to the late and the position
• so we're calculating the vector the lighting vector is doing the
• leg position
• the difference from the leg position
• on the vertex so for each each vertex are going to do that
• calculation. So the angle is going to be
• but I have
• to change the source or the direction of where the light is
• coming from. Let's say want to be obtuse angle coming on to the
• object move that also be defined in here or is that
• well we can change the light position
• so here we putting it at the same position we start out with
• the same position as the
• right but how do we change it? How do we tell it that?
• I mean I get it but we're setting it at the same point of
• the viewing point like the eye and the light is coming from the
• same point but if you have to say the eyes coming straight
• towards the object while the light is shining on the top.
• Okay, so let's think about
• where we want that to be
• so let's change it
• so let's let's make it not let's make it to it's
• so this will put
• the lady in position above the queue fairly close to the queue.
• To try that.
• So we got a kind of interesting highlight there
• let's change the lighting position a little bit more was
• put a little bit towards the viewer as well. So to still be
• involved but just a little bit
• see these
• these are fun to play with. Yeah.
• And think about
• from from our human side computing perspective. I can see
• all your smiling faces. If you think about human centered
• computing perspective, we want to think about the my
• frustration with these examples as they are is that it's not
• they're not the interesting things to manipulate aren't made
• accessible. So that's part of what would be interesting here I
• think to
• just change the direction of
• yeah so you can
• we can make the interface work more available, so we can
• understand, see what's going on.
• So there's some other thing websites
• I want to show you as well. I'll do that before too long here.
• It's a time Raven so let's see what we did here. With this and
• then.
• Hear you can see an artifact
• of two triangles on the surface
• anyway
• it's more noticeable than when he added as I said related 20
• Because the difference in angles between different vertices are
• more pronounced.
• So this is from WebGL one
• but if I was kind of needed
• I need animation so you can see in the shader So, we're passing
• the colors
• so you have a color associated with each vertex and then
• fragment shaders doing the interpolation.
• So that's that's the way this is happening here and in this
• fragment shader
• specifying the vertex color as an out and then in the fragment
• shader we specify the color hasn't been masking out the
• fragment color
• so the fragment color
• value interpolated from vertex colors.
• going to
• show you a spotlight example. as well.
• Three Jas
• so the lines there are an addition or a helper to see
• where the spotlights are being defined
• anyway
• that's the other question I want to get
• the demo that
• we just created. With the cube, we are not taking into
• consideration any shadow of the object. Like with the light
• source, we're not changing the position of the shadow or or
• showing any shadow on the object.
• Now we're not it's nothing there to
• he's not he's not
• there isn't anything there. It's
• like a sort of face should
• cast a shadow on
• you like so
• make sense? Like not like a plane so would it not change
• some areas around the canvas itself? Which is being blocked
• by the light? Let's say that Candice is getting has an
• ambient light. And then there is light that is coming in from
• like you don't have to Sandy will that not be diffused onto
• the canvas as well. For housing message that do we not do or do
• we just consider the object in a vast empty space
• basically
• suing so in computer graphics, I mean we think we don't have the
• same idea of the arrangement of so many things are handled for
• us in the real world. You know, so there are walls that of
• making lunch which we can cast shadows and add some realism but
• with a computer graphics model, we have to describe everything.
• Everything so if we need to add, add a feature we need to add it
• add it to the scene so we can
• Okay, so all I'll take that on as and we'll we'll talk about
• that. On Monday. We'll take the shader cube example and add
• shadows. Add a place for them to appear and make sure there
• we'll deal with all that okay
• so these web pages here that I I'm flashing here I'll put them
• in links for for you to look at the meeting. Notes.
• So this one is using
• her fragment shading I just want to just show what's going on
• here
• it's not very well documented here. So we have the light
• which isn't used
• so he's making some assumptions about think the viewer is at the
• origin here
• so he is for the eye so the idea is we're getting a GL position
• based on our projection so this is in our clip coordinates
• and then
• sort of passing out the normal vertex lighting vector for the
• vertex
• vector which is a viewer position relative to the vertex.
• So those three vectors are being passed to the fragment.
• outputting the vector not putting the fragment so here
• we're doing
• calculating the halfway vector
• during the diffuse
• so the idea here is a missed example. We're doing the
• interpolating the vectors for
• so we're at the vertices for calculating the normal relating
• back here and of your position vector with respect to each
• vertex, and we're passing those to the fragment shader, and then
• we're doing essentially the same computations we did in the
• shading cube exam example. But I'll create another version of
• the shaded cube which uses a per fragment shading so you can
• compare the two of them.
• I just found a website. When do you think we can reach this
• level?
• Quickly just discuss the code of this
• insurance what why once you one Can you post the
• URL? Sure.
• This like when I started work, so there used to be this website
• called Code rocks. I'm sure you all have it in palace wardrobes.
• I used to just grow through it every day. Like I have a huge
• bookmark for all these WebGL things and I've always wondered
• how they used to do and I just remembered when you showed that
• you that I saw one of those add that to the to add that to the
• notes. Actually, you can add to the discussion. Yeah, that'd be
• good please.
• CMRA things getting more clear.
• So we'll take on
• the suggestions, the shadows and so on. We'll talk about that on
• Monday and then we'll also get into chapter seven.
• Okay, sounds good. Thank you for today.
• I'll try and remember to keep my writing in the top half of the
• board
• and if anyone wants another treat
• you come
• and get them as you leave
• Thank you for today.
• Thank you for today.

Responses

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

• We continued on shading and lighting. Studied about Phong shading, reflectance,
• I would like to know more about bling Phong and reflectance. On the other hand it's was really important to know about interpolation and all the practical examples in class.
• I would like to know more the reason behind the reflection or shadow on the tube surface' artifacts seem like a triangle shape.