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Pixar in a Box – Khan Academy

pixarinabox.org

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Re: Pixar in a Box – Khan Academy

#11

Post by Paul_S »

britcruise wrote: post #2

Hey HN! My name is Brit Cruise and I'm the lead content developer on the Khan Academy side of this equation (working alongside Tony DeRose from Pixar...plus a village of others), if you have any specific questions about this project I'll be happy to answer as best I can.

I'm trying out different videos and I can't find ANY instructional content in them - I mean in terms of technical information, something applied that you can learn and use. It feels like watching a TED talk and not a Khan academy lecture!

Re: Pixar in a Box – Khan Academy

#12

Post by tbabb »

ginko wrote: post #8

It's interesting that the Rendering chapter only covers ray tracing, while most classic Pixar movies were actually mainly rendered using the Reyes algorithm, which is a form of rasterization.

Pixar movies from Finding Dory onward will be exclusively raytracing, FWIW.

Re: Pixar in a Box – Khan Academy

#13

Post by tinco »

britcruise wrote: post #2

Hey HN! My name is Brit Cruise and I'm the lead content developer on the Khan Academy side of this equation (working alongside Tony DeRose from Pixar...plus a village of others), if you have any specific questions about this project I'll be happy to answer as best I can.

I love Khan Academy, I used it extensively to practice calculus and I think also discrete mathematics back in college.

I just watched the videos of the first few sections of this math course and they're all very nice and I feel I really understand how to draw parabolas now, but the section I just watched ends with a proof.

I'm not convinced by the proof at all, it goes very fast through the basics and is very quick to point out the different relations between the ratios and the points. Now I know I've never been very quick with proofs, and I know the whole idea of Khan Academy is that you can pause and replay whenever you like, but I feel just a video isn't enough to explain even a simple geometric proof like this. Did you test this on any students? Could they reproduce the proof?

(p.s.: many events cause a bar to appear on the top of the page that pushes the entire page down, that's very not-done in web ux and causes disorientation and frustration with the user especially if the site is slow to respond (which the site is for me))

Re: Pixar in a Box – Khan Academy

#14

Post by ChicagoBoy11 »

Wonderful initiative -- wish this was around when I was in school.

Any projects in the works to tie this into Khan Academy's CS offerings? I work at a school which is about to pilot a programming class with 3d animation, but I found the content which you guys have put up to be far more engaging. If there were an accompanying suite where students could code and render an entire scene (especially if some Pixar assets were included!) it would absolutely be incredible and a great resource, and I certainly wouldn't hesitate one second to transition our course into it.

Re: Pixar in a Box – Khan Academy

#15

Post by VikingCoder »

britcruise wrote: post #2

Hey HN! My name is Brit Cruise and I'm the lead content developer on the Khan Academy side of this equation (working alongside Tony DeRose from Pixar...plus a village of others), if you have any specific questions about this project I'll be happy to answer as best I can.

I've been lucky to see Tony DeRose, Alvy Ray Smith, and a few others give presentations in small, intimate settings at my local University.

Is there some way we could please SUBSCRIBE to notifications that wonderful speakers like these are coming to our area?

Okay, yes, I know this isn't your job, but please... you might be able to help me! :)

Re: Pixar in a Box – Khan Academy

#16

Post by wbhart »

Paul_S wrote: post #11
britcruise wrote: post #2

Hey HN! My name is Brit Cruise and I'm the lead content developer on the Khan Academy side of this equation (working alongside Tony DeRose from Pixar...plus a village of others), if you have any specific questions about this project I'll be happy to answer as best I can.

I'm trying out different videos and I can't find ANY instructional content in them - I mean in terms of technical information, something applied that you can learn and use. It feels like watching a TED talk and not a Khan academy lecture!

I just watched the first two sequences of videos and so far they have shown how to compute midpoints of lines and how to compute the coordinates of points on parabolic arcs given three arbitrary control points, including how to prove the identities involved. They then explain how this is used in practice to generate the shape of a blade of grass. Is this not the kind of technical information you were expecting to find?

Re: Pixar in a Box – Khan Academy

#17

Post by thespace123 »

britcruise wrote: post #2

Hey HN! My name is Brit Cruise and I'm the lead content developer on the Khan Academy side of this equation (working alongside Tony DeRose from Pixar...plus a village of others), if you have any specific questions about this project I'll be happy to answer as best I can.

Are you going to add this content to your iOS app? Also my friend is looking forward to that Android app!!

Re: Pixar in a Box – Khan Academy

#18

Post by wbhart »

tinco wrote: post #13
britcruise wrote: post #2

Hey HN! My name is Brit Cruise and I'm the lead content developer on the Khan Academy side of this equation (working alongside Tony DeRose from Pixar...plus a village of others), if you have any specific questions about this project I'll be happy to answer as best I can.

I love Khan Academy, I used it extensively to practice calculus and I think also discrete mathematics back in college. I just watched the videos of the first few sections of this math course and they're all very nice and I feel I really understand how to draw parabolas now, but the section I just watched ends with a proof. I'm not convinced by the proof at all, it goes very fast through the basics and is very quick t…

The proof starts with two of the "string-art" lines, a line L1 (line Q'R' in the video) with parameter s and a line L2 (line QR in the video) with parameter t, and computes the intersection point P of these two lines. Keeping line L2 fixed, one gets a series of intersection points P as one varies the parameter s. One then notices that the point of intersection of line L2 and the parabola (the "touching point") is the limit of these intersection points P as s tends toward the value t. The proof finishes by showing that this limit point is just what it was hypothesised to be, namely the point along line L2 that divides it in the same proportions as its endpoints divide the control lines.

I agree that some students will not recognise the crux of the proof, but will simply see something ends up being equal to something else in some identity without understanding how that relates to what was being proved.

Euclid's Elements (an ancient Greek textbook on Geometry) is a good model in this regard. He first states what he is to prove. He then starts from the assumptions and finishes with what he was to prove. Each step in between is justified.

Re: Pixar in a Box – Khan Academy

#19

Post by tomvbussel »

ska wrote: post #10
ginko wrote: post #8

It's interesting that the Rendering chapter only covers ray tracing, while most classic Pixar movies were actually mainly rendered using the Reyes algorithm, which is a form of rasterization.

Isn't Reyes essentially a speed hack [1]? As so, is it particularly relevant to learn about today in introductory material? [1] by which i mean, inferior estimation of BSDF on/in model, but much much faster.

The REYES algorithm is an algorithm that can very quickly produce batches of shading points (with the required information to shade them such as the viewing direction). It's not really a hack and you can still use path tracing (with BSDFs) to correctly shade these points. In fact this is what Pixar did for Monster's University; they used the REYES algorithm to determine shading points visible from the camera and then shaded those using BSDFs and path tracing. The problem with this is that you basically have to store the scene twice: once for rasterization and once for ray tracing.
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