Updated the Gregory patch tessellation shaders to account for
transition edges.
Changed the implementation of OsdGetTessParameterizationTriangle()
to take the input parametric location as a 3-component value. This
allows the edge parameterization to be more numerically robust and
consistent.
Also, corrected some minor discrepancies between the various
tessellation shader configurations.
- replaced use of "LimitPoints" functions in all patch shaders
- removed the unreleased "LimitPointsTriangle" functions
- added internal tess functions for processing patch boundaries
- updated Bezier quad and tri tess evaluation to use boundary functions
Added a size specifier to the shader output array declaration
in the BSpline control shader. This seems to be required by the
GLSL compiler on AMD and is harmless elsewhere.
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.
Cleaned up the Legacy Gregory shader source by accessing buffer
data through helper functions.
Switched to performing tessellation in untransformed (object) space.
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*().
computes edge lengths using limit surface points. Made this
the default screen-space metric so that we avoid cracks when
using Gregory Basis or Regular B-spline end caps.
The alternative method which computes edge lengths using the
distance between B-spline control points is still available.
Added a diagram and comments to explain how the control
points and limit points are organized.
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.
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:
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the License and to reproduce the content of the NOTICE file.
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KIND, either express or implied. See the Apache License for the specific
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- 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
