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Pixar's Chris Horne Sheds New Light on Monsters University

thisanimatedlife.blogspot.com

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Re: Pixar's Chris Horne Sheds New Light on Monsters University

#101

Post by gdubs »

joshuak wrote: post #10

Actually there's some incorrect information here, Pixar started using ray tracing in films as far back as A Bug's Life. I can't find a picture on line but you can see it in the scene with the glass bottle. That was done by integration with a separate render but since then RenderMan as added support for GI and other ray tracing features. I'm sure this update is significant, and sounds like a ground up reworking of the…

Yep. A "Ray Server" technique where PRMan farmed out calls trace() calls to BMRT was used in "A Bug's Life" for the glass bottles at the grasshopper's hideout. All other reflection and refraction were done using 'standard-issue' environment maps.

Source: Apodaca,Gritz, Advanced Renderman -- MK 2000.

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#102

Post by [deleted] »

grecy wrote: post #38
jarrett wrote: post #31

For a bit of background: The article talks a lot about global illumination. Here's what that means. First, you have to understand the cheaper alternative, which is called local illumination. With local illumination, for each pixel, you figure out what object you're looking at, and where on that object. You take into account the normal (direction of the surface at that point) and the optical properties of the object a…

> So it's understandable that Pixar, which has to render a huge number of frames at huge resolutions, did not traditionally use it much. Do we have any ball-park estimate of how long it takes Pixar to render a single frame of a movie like Monsters U? EDIT: Many people are mentioning it's done massively parallel, which I meant to include in my question. So, what I mean is, how long does it take to render a whole Pixar…

[deleted]

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#103

Post by Tloewald »

splt wrote: post #78
berkut wrote: post #61

Earlier quoted context omitted.

Yes, because the article (and the person in it) doesn't seem to understand the difference between path tracing (ray tracing with global illumination - multiple bounces even with diffuse surfaces), and ray tracing = sending rays around a scene and bouncing them off specular reflective/refractive surfaces - which Pixar have been doing for years. It's been possible to write raytraced shaders in PRMan for over 12 years n…

Cars was in production about 10-12 years ago. Maybe you're thinking Cars 2?

The reflections on Buzz's helmet in Toy Story (the original) looked raytraced to me, although it might have been very well faked.

I usec renderman in the mid 90s and it allowed selective raytracing per shader.

Certaingly the guts at cgsociety think there was raytracing in both Toy Story and A Bug's Life.

http://forums.cgsociety.org/archive/index.php/t-60329.html

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#104

Post by craigc »

hayksaakian wrote: post #70
aidenn0 wrote: post #49

Earlier quoted context omitted.

They must do them heavily in parallel then; otherwise it would take 170 years to render the movie.

based on the two numbers: 170 years and 11.5 hours, that means 129581.580089 tasks in parallel over 11.5 hours

I don't know for sure, but I would kind of doubt they are rendering all 130,000 frames in parallel. I would think it is more likely that when a scene is done and ready then that scene would be rendered and completed.

There are a lot of other things going into each scene other than just the rendering (storyboarding, animating, lighting, etc) so it would be silly to wait for the entire film to be done and then render all at once.

Also the 11.5 hours is the average time. Single frames could take up to 80 or 90 hours to render according to that article.

So as for how many they do in parallel that would be very interesting to find out, but I would guess possibly all the frames devoted to a single scene so that would be around 5,000-10,000 frames at once which seems somewhat reasonable considering they have 12,500 cores.

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#105

Post by pygoscelis »

Here's a paper from last summer on how Pixar is doing the computations for global illumination more efficiently with a "multiresolution radiosity caching method." http://graphics.pixar.com/library/RadiosityCaching/paper.pdf

I don't know much about graphics but maybe some of you will find it illuminating (no pun intended....)

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#106

Post by berkut »

ginko wrote: post #66
berkut wrote: post #60

Earlier quoted context omitted.

They're using uni-directional path tracing - if they're using PRMan 17 (Which I think they were), it'll probably be unbiased like with Arnold. So it's unbiased, but unidirectional, unlike LuxRender's MLT (two-way path tracing). PRMan 17's a fairly good raytracer now (Arnold was giving PRMan a bit of a kicking in this department over the last two years). All on the CPU - there's no way GPUs can cope with the size of t…

Combining bi-directional path tracing and ray differentals(needed for texture filtering and geometry subdivision) doesn't really work well together at the moment, sadly.

Ray differentials are just two extra rays one pixel up and right of the main ray to give the ray width. It's pretty trivial to keep them up to date with the main ray at surface intersections (it's technically more work, sure), but it's doable, so I don't see a problem with it.

BDPT is more concerned with the surface area of meshes and solid angles of hits, so that the light path vertex weightings can be accurate.

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#107

Post by Chronic24 »

katbyte wrote: post #96
barrkel wrote: post #94

Earlier quoted context omitted.

And less flexible, more scripted behaviour is one of the biggest things driving me away from gaming these days. Most seem to end up as a sequence of action bubbles punctuated by cut-scenes, often with super-heavy hints about the "correct" way to handle the situation - sometimes even unwinnable (through e.g. infinitely spawning enemies) until you do things the "right" way. And the resulting primary gameplay experience…

>I still miss games like Thief To that list i'll add system shock 2 and Dues Ex 1

I disagree.

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#108

Post by ars »

Chronic24 wrote: post #107
katbyte wrote: post #96

Earlier quoted context omitted.

>I still miss games like Thief To that list i'll add system shock 2 and Dues Ex 1

I disagree.

Saying "I disagree" is a pretty useless comment. Say why you disagree, or don't bother saying anything at all.

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#109

Post by DanWaterworth »

bradleyjg wrote: post #67
jarrett wrote: post #64

Earlier quoted context omitted.

Yep! Rendering is very parallelizable, thank goodness. And at more than one level: You can assign different regions of a single frame to different processors, and you can also assign different frames to different processors. It's one of those special computing problems that really can be solved by throwing more silicon at it. Which is a real blessing, considering how unworkably slow it would be otherwise.

I understand how you would break up an individual frame if you are using the 'local illumination' described in the ancestor post, but if the 'global illumination' has interactions across the entire frame, how is that compatible with parallel processing? It sounds a bit like the n-body problem, which has parallel approximation algorithms, but nothing terribly straightforward.

I believe the photons are simulated backwards; they emanate from the camera.

So you don't have to simulate the same photons lots of times for different parts of the frame. You just simulate the photons that will eventually end up in a certain part of the image.

Re: Pixar's Chris Horne Sheds New Light on Monsters University

#110

Post by jswanson »

barrkel wrote: post #94
munificent wrote: post #82

Earlier quoted context omitted.

For an interesting parallel, this is analogous to my experience with emergent gameplay when I was in the game industry. Everyone really likes the idea of emergent gameplay and the open-ended-ness and flexibility that gives you. But you sacrifice a lot of control when you go that way. This can leave game designers and producers feeling like their hands are tied when the game doesn't play the way they want. Less flexib…

And less flexible, more scripted behaviour is one of the biggest things driving me away from gaming these days. Most seem to end up as a sequence of action bubbles punctuated by cut-scenes, often with super-heavy hints about the "correct" way to handle the situation - sometimes even unwinnable (through e.g. infinitely spawning enemies) until you do things the "right" way. And the resulting primary gameplay experience…

'Dark Souls' and 'Demon Souls' do this extremely well I feel.

Team Ico games come close too.

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