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Pixar Universal Scene Description

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Re: Pixar Universal Scene Description

#5

Post by TeMPOraL »

mrmrben wrote: post #3
xorgar831 wrote: post #2

That's interesting they didn't just collaborate on alembic.io, despite being sister companies.

Alembic is a baking format. Slightly different use cases. Usd has support for Alembic baked nodes: https://github.com/PixarAnimationStudios/USD/tree/2eb01f5cd4...

Could you explain what "baking" means in computer graphics?

I spent a few minutes googling, and all I've learned so far is that:

- there isn't "baking", there's "texture baking", "light baking", and many other " baking"

- it seems to mean any kind of precomputing stuff

- apparently the term was coined by Pixar in some paper

Re: Pixar Universal Scene Description

#6

Post by Keyframe »

TeMPOraL wrote: post #5
mrmrben wrote: post #3

Earlier quoted context omitted.

Alembic is a baking format. Slightly different use cases. Usd has support for Alembic baked nodes: https://github.com/PixarAnimationStudios/USD/tree/2eb01f5cd4...

Could you explain what "baking" means in computer graphics? I spent a few minutes googling, and all I've learned so far is that: - there isn't "baking", there's "texture baking", "light baking", and many other " baking" - it seems to mean any kind of precomputing stuff - apparently the term was coined by Pixar in some paper

baking, in this context is a stream of vertices where each frame carries geometry information and nothing else.

If geometry wasn't baked in, then you would have a separate description of geometry (and everything else) as well as keyframes which are left to the client to interpolate.

Think of it as a HTML versus a screenshot. Both carry the same information, but for screenshot you don't need anything else apart from image viewer. For HTML you need parser, layout, render, whatever.. poor analogy, but hey.

USD is a next generation RIB, like OSL (done at sony) is next gen RSL. Both RIB and RSL stem from RISpec https://en.wikipedia.org/wiki/RenderMan_Interface_Specificat... which is a good intro to see what's being talked about here.

Re: Pixar Universal Scene Description

#7

Post by CyberDildonics »

TeMPOraL wrote: post #5
mrmrben wrote: post #3

Earlier quoted context omitted.

Alembic is a baking format. Slightly different use cases. Usd has support for Alembic baked nodes: https://github.com/PixarAnimationStudios/USD/tree/2eb01f5cd4...

Could you explain what "baking" means in computer graphics? I spent a few minutes googling, and all I've learned so far is that: - there isn't "baking", there's "texture baking", "light baking", and many other " baking" - it seems to mean any kind of precomputing stuff - apparently the term was coined by Pixar in some paper

> precomputing stuff

Correct. In this context it means turning the geometry into frame by frame mesh data so that your animation isn't dependent on anything like bones, cloth simulation, muscle/skin simulation, soft or rigid body dynamics, inverse kinematics in the rig, expressions on the bones of the rig etc.

Not only does it break dependencies, but it is also easier to get that geometry into another part of the pipeline like effects, lighting and even compositing.

Re: Pixar Universal Scene Description

#8

Post by generic_user »

TeMPOraL wrote: post #5
mrmrben wrote: post #3

Earlier quoted context omitted.

Alembic is a baking format. Slightly different use cases. Usd has support for Alembic baked nodes: https://github.com/PixarAnimationStudios/USD/tree/2eb01f5cd4...

Could you explain what "baking" means in computer graphics? I spent a few minutes googling, and all I've learned so far is that: - there isn't "baking", there's "texture baking", "light baking", and many other " baking" - it seems to mean any kind of precomputing stuff - apparently the term was coined by Pixar in some paper

An animated scene is broken down into frames. In each frame there is usually geometry that is moving. Each piece of geometry is a collection of polygonal data that has (xyz) points as its basic primitive.

It is often convenient, sometimes necessary to store point data into an off-line file for each frame of the animation. That point data is called a bake.or a point cache.

For instance if you do a simulation that takes 4 hours to solve you would absolutely want to bake out each frame of the point geometry. Then you can load that data into ram and play back the simulation inside of a modeling/animation program in real time.

There are many other uses for geometry baking.

Re: Pixar Universal Scene Description

#9

Post by adrianm »

TeMPOraL wrote: post #5
mrmrben wrote: post #3

Earlier quoted context omitted.

Alembic is a baking format. Slightly different use cases. Usd has support for Alembic baked nodes: https://github.com/PixarAnimationStudios/USD/tree/2eb01f5cd4...

Could you explain what "baking" means in computer graphics? I spent a few minutes googling, and all I've learned so far is that: - there isn't "baking", there's "texture baking", "light baking", and many other " baking" - it seems to mean any kind of precomputing stuff - apparently the term was coined by Pixar in some paper

That's exactly right. It's just a general term nowadays for embedding pre-computed information into an asset for the purposes of optimizing the rendering of that asset. Of course, you need a renderer capable of understanding how to make use of this information to properly reconstruct the scene, hence standardization like the Alembic format is useful.
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