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Pixar's Chris Horne Sheds New Light on Monsters University

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

#61

Post by berkut »

ubercow13 wrote: post #59
berkut wrote: post #37

This is wrong actually - they've been using ray tracing for ages (all ambient occlusion in PRMan is done with raytracing, by sending out occlusion rays in a hemisphere around the shading point). What's new with MU is they're using both physically-plausible shading (where the shading is based off physically-based BRDF lighting algorithms, which gives much more realistic results), and global illumination path-tracing f…

They explain the extent to which they used to use raytracing in the article - is it misrepresented? It's in a direct quote so I doubt it.

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 now.

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

#62

Post by berkut »

joshuak wrote: post #27
glut wrote: post #9

What sort of raytracing are they using? Are they going all the way to an unbiased global light transport algorithm (like LuxRender) or just using basic raytracing (like PovRay)? Are they using an existing renderer? If not, are they releasing their own like they did with RenderMan? Are they rendering with CPUs or with GPUs? How much time per frame does it take them with how many cores of what sort?

Interesting questions. I don't have the answers, but I can say that I can't imagine that Pixar would ever 'go all the way' to an 'unbiased' GI renderer. Our entire function in the filmmaking business is to tell a story visually, and for that you need complete control and directability of the image. This is the opposite goal of unbiased renderers. Nevertheless more tools in the tool box is always good.

Unbiased actually isn't slow - Arnold has proved this - what's slow is using hundreds of bounces per path and bi-directional path tracing (like Maxwell, Indigo, LuxRender) which takes a lot longer.

Biased generally means it's interpolated with a point or irradiance cache.

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

#63

Post by baby »

mratzloff wrote: post #57

I was wondering what Toy Story would look like if they re-rendered it with today's technology. Well, it turns out they already did! It was part of the theatrical re-releases of Toy Story and Toy Story 2 in 3D. http://www.bigscreenanimation.com/2008/09/toy-story-re-relea... Were these re-rendered versions released in 2D on Blu-ray?

I wonder if you really see a difference.

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

#64

Post by jarrett »

aidenn0 wrote: post #49
Jabbles wrote: post #42

Earlier quoted context omitted.

11.5 hours on average for Cars 2 http://news.cnet.com/8301-13772_3-20068109-52/new-technology...

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

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.

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

#65

Post by ginko »

kyberias wrote: post #15
uptown wrote: post #4

Earlier quoted context omitted.

Larger versions: http://bluraymedia.ign.com/bluray/image/article/104/1044870/... http://pixartimes.com/wp-content/uploads/2012/08/Monsters-Un...

Wow! There's actually a huge difference! Not that I'm really surprised but still.

You also have to consider that Monsters Inc. was one of the earlier Pixar movies.

The contrast to Brave isn't that extreme.

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

#66

Post by ginko »

berkut wrote: post #60
glut wrote: post #9

What sort of raytracing are they using? Are they going all the way to an unbiased global light transport algorithm (like LuxRender) or just using basic raytracing (like PovRay)? Are they using an existing renderer? If not, are they releasing their own like they did with RenderMan? Are they rendering with CPUs or with GPUs? How much time per frame does it take them with how many cores of what sort?

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.

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

#67

Post by bradleyjg »

jarrett wrote: post #64
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.

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.

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

#70

Post by hayksaakian »

aidenn0 wrote: post #49
Jabbles wrote: post #42

Earlier quoted context omitted.

11.5 hours on average for Cars 2 http://news.cnet.com/8301-13772_3-20068109-52/new-technology...

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
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