Catmull-Clark Subdivision Surfaces", Niessner et al, Eurographics 2012.
This change includes;
-topology identification for single-crease patch during adaptive refinement.
-patch array population (similar to boundary)
-sharpness buffer generation
-glsl shader
Eval stuffs will be coming.
All kernels take offset/length/stride to apply subdivision partially in each vertex elements.
Also the offset can be used for client-based VBO aggregation, without modifying index buffers.
This is useful for topology sharing, in conjunction with glDrawElementsBaseVertex etc.
However, gregory patch shader fetches vertex buffer via texture buffer, which index should also
be offsetted too. Although gl_BaseVertexARB extension should be able to do that job, it's a
relatively new extension. So we use OsdBaseVertex() call to mitigate the compatibility
issue as clients can provide it in their way at least for the time being.
Important notice: all client shader code must have following functions and compose them to osd intrinsic shaders (vertex/tessEval/tessControl)
mat4 OsdModelViewMatrix()
mat4 OsdProjectionMatrix()
mat4 OsdModelViewProjectionMatrix()
float OsdTessLevel()
int OsdGreogryQuadOffsetBase()
int OsdPrimitiveIdBase()
We probably should write a utility class for basic binding of them, to make client code simpler.
New text:
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.
- Added OSD_ prefix to preprocessor symbols
- Adjusted transition sub-patch parameterization to be
consistent with non-transition patches
- Unified BSpline shader code
- Removed duplicate Boundary, Corner, and Transition shader source
- Fixed a few discrepancies in the remaining duplicate code paths
- defined a fallback value for ROTATE
- made GetPatchLevel() a macro to avoid
referencing gl_PrimitiveID from vertex shaders
- fixed float array initializers
- replace ptex indexing with the FarPtexCoord structure as a way to pass per-patch
ptex data to the shaders.
We are replacing a vector<int> arranged as :
int[0] : ptex face index
int[1] : (u,v) as 16 bits encoding the log2 coordinate of the top left corner
Instead we are now using a struct arranged as :
int[0] : ptex face index
int[1] : is a bit-field containing u,v, rotation, depth and non-quad
The u,v coordinates have been reduced to 10 bits instead of 16, which still
gives us a lot of margin.
- Replace OsdVertexBufferDescriptor with something more adequate for general
primvar representation (this name will probably eventually change...)
- Improve OsdPatchDescriptor
- add a "loop" boolean (true if the patch is of loop type)
- add a GetPatchSize() accessor
- OsdPatchArray :
- remove some redundant elements (still more to do there)
- Fix all shader / examples / regressions & stuff to make this all work.
fixes#143
2 client APIs are changed.
- VertexBuffer::UpdateData() takes start vertex offset
- ComputeController::Refine() takes FarKernelBatchVector
Also, ComputeContext no longer holds farmesh.
Client can free farmesh after OsdComputeContext is created.
(but still need FarKernelBatchVector to apply subdivision kernels)
This avoids adaptive tessellation artifacts near silhouette edges
by using the projected diameter of an edge's bounding sphere
rather than the length of the projected edge itself.
There is a nice writeup of this by Bryan Dudash of NVIDIA at:
https://developer.nvidia.com/content/dynamic-hardware-tessellation-basics
- [Feature Adaptive GPU Rendering of Catmull-Clark Surfaces](http://research.microsoft.com/en-us/um/people/cloop/tog2012.pdf).
- New API architecture : we are planning to lock on to this new framework as the basis for backward compatibility, which we will enforce from Release 1.0 onward. Subsequent releases of OpenSubdiv should not break client code.
- DirectX 11 support
- and much more...
