This change refactors the GLSL and HLSL patch shader code so that
most of the work is implemented within a library of common functions
and the remaining shader snippets just manage plumbing.
There is more to do here:
- varying and face-varying data can be managed entirely by the client
- similarly, displacement can be implemented in client code
- there's still quite a bit of residual boiler-plate code needed
in each shader stage that we should be able to wrap up in a more
convenient form.
Remove DrawRegistry from osd layer and put a simple shader caching
utility into examples/common. osd layer only provides patch shader
snippet and let client configure and compile the code. Clients also
maintain the lifetime of shader object, which is preferable for the
actual application integration.
update all examples to use the new scheme.
Each patch has a corresponding patchParam. This is a set of three values
specifying additional information about the patch:
faceId -- topological face identifier (e.g. Ptex FaceId)
bitfield -- refinement-level, non-quad, boundary, transition, uv-offset
sharpness -- crease sharpness for a single-crease patch
These are stored in OsdPatchParamBuffer indexed by the value returned
from OsdGetPatchIndex() which is a function of the current PrimitiveID
along with an optional client provided offset.
Accessors are provided to extract values from a patchParam. These are
all named OsdGetPatch*().
While drawing patches, the patchParam is condensed into a patchCoord which
has four values (u, v, faceLevel, faceId). These patchCoords are treated
as int values during per-prim processing but are converted to float values
during per-vertex processing where the values are interpolated.
Also, cleaned up more of the shader namespace by giving an Osd prefix
to public functions, and consolidated boundary and transition handling
code into the PatchCommon shader files. The functions determining
tessellation levels are now all named OsdGetTessLevel*().
Sync'ing the 'dev' branch with the 'feature_3.0dev' branch at commit 68c6d11fc36761ae1a5e6cdc3457be16f2e9704a
The branch 'feature_3.0dev' is now locked and preserved for historical purposes.
