The Chaikin crease interpolation mode seems to be broken:
- Catmark / Loop / Bilinear are passing the wrong halfedge vertex to the
SubdivideCreaseWeight function which results in sub-edge crease weights
being swapped
- the loop that iterates over adjacent edges needs to check against both
the original edge and its opposite, otherwise it may be incorrectly
accumulated into summation of these adjacent edges (with a 0.25 weight)
The proposed fix:
- Swaps the Dest/Org vertex passed to the SubdivideCreaseWeight (and
we probably want Julian to confirm that this the correct fix)
- Checks against both the original edge and its opposite in the iteration
over adjacent edges
- Replaces the std::vector based query with an HbrHalfedgeOperator for
better performance (hopefully)
The similar fix to OpenSubdiv been reviewed by Tony DeRose.
Also in the fix:
- fix "obj" tag parsing of the smooth triangle tag that was incorrectly
associated with the crease method (and reporting the wrong errors)
- add regression shapes for both Loop & Catmark schemes to hbr_regression
- add same shapes to the glViewer
- improve hbr_regression output to be more readable
- add command-line argument parsing to hbr_regression
- add functionality to dump an obj file when regression fails for comparison
fixes#235
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- add tag parsing for h-hole in shape_utils
- re-create Renderman's test shape from the documentation (catmark_square_hedit.h)
- fix Hbr to correctly pass the hole tag from parent to child face
- fix FarSubdivisionTables to handle disconnected face-vertices without crashing
fixes#75
- make sure HBR passes down the hole tag to children when subdividing faces
- minor API modification : allow to unset the hole flag on a face
- modify uniform / adaptive FarMeshFactory to be aware of the flag
- make the FarSubdivisionTableFactory assert when finding unconnected HBR vertices (as it should)
* Uniform subdivision :
The refinement scheme only creates faces & vertices necessary
to maintain the one-ring around the edges of a hole, so this solution
is quite efficient.
* Adaptive subdivision :
At the moment we are still performing full topological analysis on holes and
only skipping patches associated to holes. This is sub-optimal in 2 ways :
1. the topological analysis can potentially be cranking on a lot of unnecessary
geometry
2. even though we may not be drawing the patches, the compute stage is still
applying kernels on all the control vertices of these patches.
We will have to revisit feature adaptive subdivision & holes, so keep the issue active.
fixes#78
- [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...
