How Pixar changed the way light works

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Old 06 June 2013   #1
How Pixar changed the way light works

Pretty interesting article on the work that went into monsters university and their new Global Illumination System. Looking forward to seeing it this weekend.

http://www.theverge.com/2013/6/21/4...ters-university
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Old 06 June 2013   #2
Interesting. Would love to see a more technical in-depth article about this. Going from this one though, it seems like they've used GI like many of us have been doing for a while now. So the real breakthrough would be the scale of the project? Or did they change the way of how their GI works?
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Old 06 June 2013   #3
I'll dare venture it's just PRMan and Pixar finally almost catching up to the rest of the world in terms of lighting and rendering mechanics
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Old 06 June 2013   #4
Didn't Shrek 2 use GI? That was almost a decade ago. Way to finally catch up, Pixar.
 
Old 06 June 2013   #5
back in 2002 Paul Debevec showed how HDRI images could be used to light scenes. What I believe the article meant was Pixar is the first to use GI for the entire movie, not just sections of a movie.
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Old 06 June 2013   #6
I don't get it. Shouldn't the article be titled something along the lines of 'Throwing rays: How Pixar changed its lighting pipeline'?

They've used point clouds prior to this, with some dabbles in raytraced GI, have they not? GI cheats are perfectly fine for animated features - just ask Dreamworks. Go ahead.

Dreamworks knows.
 
Old 06 June 2013   #7
Pixar have been using Global Illumination techniques in their films for a good while. What's new here is Monsters U and Blue Umbrella are using PRMan's new plausible shading system - which is an upgrade to the shading language and the renderer to improve it's raytracing abilities. It was already pretty good at raytracing some things, but there were certain things which were either slow (area light shadows, indirect diffuse) or you couldn't compute them via raytracing (subsurface) and required the use of point clouds or maps. It also now natively supports multiple importance sampling of image based lighting.

There is nothing artistically here they're doing that they couldn't do before, the change is purely a technical one - in that you don't need to do any pre-passes - which in most renderman workflows is a fairly transparent operation for an artist anyway, not too different from using irradiance caches in other renderers.
 
Old 06 June 2013   #8
and from the title description, here I was thinking they invented some new revolutionary lighting algorithm that hasn't been done before.

Looks good though. That always seems to be the trend - to abuse a lower end tool/technique until it becomes apparent that something new that previously was too expensive will look nicer and save time in the long run
 
Old 06 June 2013   #9
interesting about RAM

That's a lot to keep in RAM. The biggest struggle was to keep each frame down to 20GB of memory. Pixarís render farm uses machines with 96GB of RAM each, but since the machines need to process four frames in parallel, anything much higher than 20GB was dangerous. That might seem like a lot for a single frame, but it has to hold every object in the scene, on-and-off camera, right down to the hairs of each monsterís fur. As long as itís reflecting light, it needs to be in memory. And if any of those hairs move, the light has to be completely recalibrated ó usually in another overnight turn through the render farm.


they are talking about the Radiosity caching right?
 
Old 06 June 2013   #10
While not more technically in-depth, there are some nuggets of info in this interview with Chris Home who worked on Pixar's new lighting system: http://thisanimatedlife.blogspot.ca...ght-on.html?m=1
 
Old 06 June 2013   #11
 
Old 06 June 2013   #12
Quote:
Originally Posted by pomru
While not more technically in-depth, there are some nuggets of info in this interview with Chris Home who worked on Pixar's new lighting system: http://thisanimatedlife.blogspot.ca...ght-on.html?m=1


woooow. Pixar has a lot detail and a lot fur. wow.

''True reflection and refraction in the eyes reflecting actual SCENE GEOMETRY and not a brickmap. Yep - we're refracting through the cornea onto the sclera and iris. Oh and all your shadows are raytraced now - no more shadowmaps. Nope. None.''
 
Old 06 June 2013   #13
Quote:
Originally Posted by unclebob
back in 2002 Paul Debevec showed how HDRI images could be used to light scenes. What I believe the article meant was Pixar is the first to use GI for the entire movie, not just sections of a movie.

They're not, this is just Pixar using extensively the last two or three years of push to dig renderman out of the Jurassic (which they did with relatively good success).

Anything Sony rendered in Arnold (and those date quite a few years back) would already have gone by similar models.
Our work on WWD the movie did the same, and that was PRMan's plausible stuff, and the same goes for a long list dating a while back.

If it wasn't Pixar it probably wouldn't even have got coverage being it's a catch-up.

Don't get me wrong, they produce stellar work, and revitalizing PRMan the way they did while retaining its pipeline and shader friendliness was a great job, but as far as technology and shading/lighting models go this is just now a short distance behind a curve they were years behind on.
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Old 06 June 2013   #14
Basically this is Pixar's answer to Arnold. It's cheaper and faster to let the computer do some serious number crunching rather than an artist spending more time trying to achieve the same look. Not saying that this is necessarily easier in the long run, but it's definitely more efficient in terms of artist time vs computer time. And if an artist is waiting, just give him/her more shots!
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Old 06 June 2013   #15
Keep in mind that the site this article is on is a general tech site, not aimed at CG professionals, so the terminology has been dumbed down. I was very interested to see snippets in the accompanying video of their proprietary animation software (still called Marionette ?) as it looks much more refined than what I have seen in previous videos.

Seems it is now based on viewport manipulation as compared to the old system of gui sliders. Also looks to have a very nice viewport opengl fur representation. Very nice clean looking gui with the f-curves laid out like that. Would love to know more from those in the know about this proprietary software, since it is not likely that I will ever get to use it

Quote:
Basically this is Pixar's answer to Arnold


Interesting....so is it a brute force GI solution or a pre-cached irradiance map style solution?
 
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