mirror of
https://github.com/PixarAnimationStudios/OpenSubdiv
synced 2024-12-27 02:10:24 +00:00
181 lines
7.0 KiB
ReStructuredText
181 lines
7.0 KiB
ReStructuredText
..
|
|
Copyright 2013 Pixar
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "Apache License")
|
|
with the following modification; you may not use this file except in
|
|
compliance with the Apache License and the following modification to it:
|
|
Section 6. Trademarks. is deleted and replaced with:
|
|
|
|
6. Trademarks. This License does not grant permission to use the trade
|
|
names, trademarks, service marks, or product names of the Licensor
|
|
and its affiliates, except as required to comply with Section 4(c) of
|
|
the License and to reproduce the content of the NOTICE file.
|
|
|
|
You may obtain a copy of the Apache License at
|
|
|
|
http://www.apache.org/licenses/LICENSE-2.0
|
|
|
|
Unless required by applicable law or agreed to in writing, software
|
|
distributed under the Apache License with the above modification is
|
|
distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
|
|
KIND, either express or implied. See the Apache License for the specific
|
|
language governing permissions and limitations under the Apache License.
|
|
|
|
|
|
Introduction
|
|
------------
|
|
|
|
.. image:: images/geri.jpg
|
|
:width: 100%
|
|
:align: center
|
|
|
|
.. contents::
|
|
:local:
|
|
:backlinks: none
|
|
|
|
----
|
|
|
|
Introduction
|
|
============
|
|
|
|
OpenSubdiv is a set of open source libraries that implement high performance
|
|
subdivision surface (subdiv) evaluation on massively parallel CPU and GPU
|
|
architectures. This code path is optimized for drawing deforming surfaces with
|
|
static topology at interactive framerates. The resulting limit surfaces are a match
|
|
for Pixar's Renderman specification within numerical precision limits.
|
|
|
|
OpenSubdiv is a code API which we hope to integrate into 3rd. party digital
|
|
content creation tools. It is **not** an application, nor a tool that can be used
|
|
directly to create digital assets.
|
|
|
|
----
|
|
|
|
Why Fast Subdivision ?
|
|
======================
|
|
|
|
Subdivision surfaces are commonly used for final rendering of character shapes
|
|
for a smooth and controllable limit surfaces. However, subdivision surfaces in
|
|
interactive apps are typically drawn as their polygonal control hulls because of
|
|
performance. The polygonal control hull is an approximation that is offset from
|
|
the true limit surface. Looking at an approximation in the interactive app makes
|
|
it difficult to see exact contact, like fingers touching a potion bottle or hands
|
|
touching a cheek. It also makes it difficult to see poke-throughs in cloth simulation
|
|
if the skin and cloth are both approximations. This problem is particularly bad when
|
|
one character is much larger than another and unequal subdiv face sizes cause
|
|
approximation errors to be magnified.
|
|
|
|
Maya and Pixar's proprietary Presto animation system can take 100ms to subdivide
|
|
a character of 30,000 polygons to the second level of subdivision (500,000 polygons).
|
|
Being able to perform the same operation in less than 3ms allows the user to interact
|
|
with the smooth, accurate limit surface at all times.
|
|
|
|
.. image:: images/osd_splash.png
|
|
:align: center
|
|
:target: images/osd_splash.png
|
|
|
|
|
|
|
|
----
|
|
|
|
Research
|
|
========
|
|
|
|
The new GPU technology behind OpenSubdiv is the result of a joint research effort
|
|
between Pixar and Microsoft.
|
|
|
|
| *Feature Adaptive GPU Rendering of Catmull-Clark Subdivision Surfaces*
|
|
| Matthias Niessner, Charles Loop, Mark Meyer, and Tony DeRose
|
|
| ACM Transactions on Graphics, Vol. 31 No. 1 Article 6 January 2012
|
|
| `<http://research.microsoft.com/en-us/um/people/cloop/tog2012.pdf>`_
|
|
|
|
|
| *Efficient Evaluation of Semi-Smooth Creases in Catmull-Clark Subdivision Surfaces*
|
|
| Matthias Niessner, Charles Loop, and Guenter Greiner.
|
|
| Eurographics Proceedings, Cagliari, 2012
|
|
| `<http://research.microsoft.com/en-us/um/people/cloop/EG2012.pdf>`_
|
|
|
|
|
| *Analytic Displacement Mapping using Hardware Tessellation*
|
|
| Matthias Niessner, Charles Loop
|
|
| ACM Transactions on Graphics, To appear 2013
|
|
| `<http://research.microsoft.com/en-us/um/people/cloop/TOG2013.pdf>`_
|
|
|
|
----
|
|
|
|
Heritage
|
|
========
|
|
|
|
This is the fifth-generation subdiv library in use by Pixar's proprietary animation
|
|
system in a lineage that started with code written by Tony DeRose and Tien Truong
|
|
for Geri's Game in 1996. Each generation has been a from-scratch rewrite that
|
|
has built upon our experience using subdivision surfaces to make animated films.
|
|
This code is live, so Pixar's changes to OpenSubdiv for current and future films
|
|
will be released as open source at the same time they are rolled out to Pixar
|
|
animation production.
|
|
|
|
| *Subdivision for Modeling and Animation*
|
|
| Denis Zorin, Peter Schroder
|
|
| Course Notes of SIGGRAPH 1999
|
|
| `<http://www.multires.caltech.edu/pubs/sig99notes.pdf>`_
|
|
|
|
|
| *Subdivision Surfaces in Character Animation*
|
|
| Tony DeRose, Michael Kass, Tien Truong
|
|
| Proceedings of SIGGRAPH 1998
|
|
| `<http://graphics.pixar.com/library/Geri/paper.pdf>`_
|
|
|
|
|
| *Recursively generated B-spline surfaces on arbitrary topological meshes*
|
|
| Catmull, E.; Clark, J. Computer-Aided Design 10 (6) (1978)
|
|
|
|
----
|
|
|
|
Licensing
|
|
=========
|
|
|
|
OpenSubdiv is covered by the Apache License, and is free to use for commercial or
|
|
non-commercial use. This is the same code that Pixar uses internally for animated
|
|
film production. Our intent is to encourage a geometry standard for subdivision
|
|
surfaces, by providing consistent (i.e. yielding the same limit surface), high
|
|
performance implementations on a variety of platforms.
|
|
|
|
Why Apache? We were looking for a commercial-friendly license that would convey
|
|
our patents to the end users. This quickly narrowed the field to Microsoft Public
|
|
License or Apache. Initially we chose MSPL because it handled trademarks better.
|
|
But at the request of several companies we gave Apache another look, and decided
|
|
to go with Apache with a very slight modification that simply says you cannot use
|
|
any contributors' trademarks. In other words, you can use OpenSubdiv to make a
|
|
product, but you cannot use a Luxo Lamp (or other character, etc.) when marketing
|
|
your product.
|
|
|
|
`License Header <license.html>`_
|
|
|
|
----
|
|
|
|
Contributing
|
|
============
|
|
|
|
In order for us to accept code submissions (merge git pull-requests), contributors
|
|
need to sign the Contributor License Agreement (CLA). There are two CLAs, one for
|
|
individuals and one for corporations. As for the end-user license, both are based
|
|
on Apache. They are found in the code repository (`individual form
|
|
<https://github.com/PixarAnimationStudios/OpenSubdiv/blob/master/OpenSubdivCLA_individual.pdf>`__,
|
|
`corporate form <https://github.com/PixarAnimationStudios/OpenSubdiv/blob/master/OpenSubdivCLA_corporate.pdf>`__).
|
|
Please email the signed CLA to opensubdiv-cla@pixar.com.
|
|
|
|
|
|
For more details about OpenSubdiv and other Pixar projects, see
|
|
`Pixar Graphics Technologies <http://graphics.pixar.com>`__.
|
|
|
|
----
|
|
|
|
External Resources
|
|
==================
|
|
|
|
Microsoft Research:
|
|
`Charles Loop <http://research.microsoft.com/en-us/um/people/cloop/>`__
|
|
`Matthias Niessner <http://lgdv.cs.fau.de/people/card/matthias/niessner/>`__
|
|
|
|
Pixar Research:
|
|
`Pixar R&D Portal <http://graphics.pixar.com/research/>`__
|
|
|
|
|
|
|
|
|