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Copyright 2013 Pixar
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Licensed under the Apache License, Version 2.0 (the "Apache License")
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with the following modification; you may not use this file except in
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compliance with the Apache License and the following modification to it:
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Section 6. Trademarks. is deleted and replaced with:
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6. Trademarks. This License does not grant permission to use the trade
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names, trademarks, service marks, or product names of the Licensor
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and its affiliates, except as required to comply with Section 4(c) of
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the License and to reproduce the content of the NOTICE file.
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You may obtain a copy of the Apache License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the Apache License with the above modification is
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distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the Apache License for the specific
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language governing permissions and limitations under the Apache License.
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Overview of Release 3.1
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=======================
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.. contents::
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:local:
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:backlinks: none
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New Features
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------------
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Bicubic Face-Varying Patches
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The motivation for this feature is to improve drawing and evaluation of face-varying
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primvar values for all
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`face-varying interpolation options <subdivision_surfaces.html#face-varying-interpolation-rules>`__.
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A common use of non-linear face-varying data is to capture a UV projection on
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the surface. The following example shows a simple shape with the face-varying
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interpolation option assigned to a non-linear choice to achieve the desired
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projection (in this case FVAR_LINEAR_NONE):
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+----------------------------------------------+----------------------------------------------+
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| .. image:: images/fvar_patch_linearall.png | .. image:: images/fvar_patch_linearnone.png |
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| :align: center | :align: center |
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| :width: 75% | :width: 75% |
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| :target: images/fvar_patch_linearall.png | :target: images/fvar_patch_linearnone.png |
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| | |
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| Linear Face-Varying Patches | Bicubic Face-Varying Patches |
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+----------------------------------------------+----------------------------------------------+
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The result on the left shows the old linearly interpolated patches, which
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ignores any non-linear settings. The result on the right shows the new use of
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bicubic face-varying patches to accurately interpolate the desired projection.
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Generation of a full face-varying patch representation can be enabled using a new option
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in Far::PatchTableFactory::Options. Additionally, topological refinement can be improved
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to consider fvar channel topology using a new option in Far::TopologyRefiner::AdaptiveOptions. See the API additions below and their associated Doxygen text
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for more details.
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Evaluation of patch basis weights for all patch types as been added to the GPU shader
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source provided by Osd::GLSLPatchShaderSource, and Osd::HLSLPatchShaderSource.
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Use of non-linear face-varying patches increases the storage size of the patch table and may also require additional data access and computation while drawing.
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Varying and Face-Varying Evaluation
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This feature extends existing evaluation methods to support evaluation of varying and face-varying
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primvar data at arbitrary limit surface locations.
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+-----------------------------------------+-----------------------------------------+
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| .. image:: images/eval_varying.png | .. image:: images/eval_facevarying.png |
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| :align: center | :align: center |
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| :width: 75% | :width: 75% |
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| :target: images/eval_varying.png | :target: images/eval_facevarying.png |
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| Varying Primvar Evaluation | Face-Varying Primvar Evaluation |
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+-----------------------------------------+-----------------------------------------+
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The image on the left shows evaluation of varying primvar values and the image on the right
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shows evaluation of face-varying primvar values.
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The EvaluateBasis API of Far::PatchTable has been extended as well as the OSD Evaluator API.
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Second Order Derivative Evaluation
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This feature extends the Far::LimitStencilTable and Far::PatchTable interfaces to support
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evaluation of 2nd order partial derivatives. The generation of derivative values
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for Far::LimitStencilTable is controlled by new options that can be specified when creating
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the stencil table.
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Additionally, the implementation exposes a more accurate method to compute derivatives
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for Gregory basis patches. This can be enabled using the CMake configuration and
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compile time definition OPENSUBDIV_GREGORY_EVAL_TRUE_DERIVATIVES.
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Separate Levels of Feature Isolation
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The primary motivation for this feature is to reduce the number of patches generated by
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adaptive refinement when they can be adequately represented at a lower level. A single
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level of isolation must be as high as the greatest semi-sharp feature to properly resolve
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the shape of that feature. That high isolation level generates many unnecessary patches
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for smooth extra-ordinary vertices.
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In the following example, a single semi-sharp vertex is refined to level 5:
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+--------------------------------------+--------------------------------------+
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| .. image:: images/sec_level_off.png | .. image:: images/sec_level_on.png |
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| :align: center | :align: center |
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| :width: 75% | :width: 75% |
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| :target: images/sec_level_off.png | :target: images/sec_level_on.png |
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| Single Isolation Level 5 | Primary Level 5, Secondary Level 2 |
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+--------------------------------------+--------------------------------------+
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Single isolation to level 5 on the left results in 312 patches. The right shows the
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semi-sharp feature isolated to 5, but with the new "secondary level" set to 2, the
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number of patches is reduced to 123.
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The second specified level of adaptive refinement is used
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to halt isolation for features that typically do not require the specified maximum.
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These include interior and boundary extra-ordinary vertices and those infinitely sharp
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patches that correspond to boundary extra-ordinary patches.
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The secondary level is available as a new option in Far::TopologyRefiner::AdaptiveOptions.
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Sharp Patches for Infinitely Sharp Features
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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The motivation for sharp patches is to accurately represent the limit surface of
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infinitely sharp features, which otherwise can only be approximated by very high levels
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of adaptive refinement, resulting in many unnecessary patches.
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The true limit surface for regular faces along an infinitely sharp crease is a
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regular B-Spline patch -- the same as regular faces along a boundary.
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Similarly, the limit surface for faces around an extra-ordinary vertex on an infinitely
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sharp crease is the same as that of faces around an extra-ordinary vertex on a boundary.
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So these patches are identified and isolated to the same degree -- the regular patches
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as soon as possible, and the irregular patches to the depth specified.
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Consider the following (regression/shape/catmark_cube_creases2):
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+------------------------------------+------------------------------------+------------------------------------+
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| .. image:: images/inf_sharp_a.png | .. image:: images/inf_sharp_b.png | .. image:: images/inf_sharp_c.png |
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| :align: center | :align: center | :align: center |
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| :width: 100% | :width: 100% | :width: 100% |
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| :target: images/inf_sharp_a.png | :target: images/inf_sharp_b.png | :target: images/inf_sharp_c.png |
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| Level 5 without Sharp Patches | Level 5 with Sharp Patches | Level 2 with Sharp Patches |
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+------------------------------------+------------------------------------+------------------------------------+
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Without use of sharp patches on the left, isolating to level 5 generates 1764 patches and does still
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not capture the sharp edges. With sharp patches in the center, isolating to the same degree (level
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5) reduces the number of patches to 96 and captures the sharp edges. The sharp features can be
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captured at a lower degree with comparable accuracy as illustrated on the right where isolation to
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level 2 further reduces the number of patches to 42.
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The use of infinitely sharp patches can be enabled both at a high level as an new option to Osd::Mesh,
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or more directly when adaptively refining or construction the patch tables in
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Far::TopologyRefiner::AdaptiveOptions and Far::PatchTableFactory::Options.
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Given the improved accuracy and reduced patches by the use of simple regular patches, we would prefer
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that this be the default behavior, but it was made an explicit option in order to avoid disrupting
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existing usage. In a future major release this feature will hopefully be the norm.
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API Additions
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-------------
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See associated `Doxygen <doxy_html/index.html>`__ for full details.
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Osd::CpuEvaluator, GLComputeEvaluator, etc:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- EvalPatchesVarying()
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- EvalPatchesFaceVarying()
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Osd::CpuPatchTable, GLPatchTable, etc:
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- GetFVarPatchArrayBuffer()
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- GetFVarPatchIndexBuffer()
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- GetFVarPatchIndexSize()
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- GetFVarPatchParamBuffer()
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- GetFVarPatchParamSize()
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- GetNumFVarChannels()
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- GetVaryingPatchArrayBuffer()
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- GetVaryingPatchIndexBuffer()
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- GetVaryingPatchIndexSize()
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Osd::MeshBits:
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~~~~~~~~~~~~~~
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- member MeshFVarAdaptive
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- member MeshUseInfSharpPatch
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Osd::PatchParam
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~~~~~~~~~~~~~~~
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- IsRegular()
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- Unnormalize()
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- extensions to Set()
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Osd::GLSLPatchShaderSource, HLSLPatchShaderSource
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- GetPatchBasisShaderSource()
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Far::LimitStencil
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~~~~~~~~~~~~~~~~~
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- GetDuuWeights()
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- GetDuvWeights()
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- GetDvvWeights()
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- extensions to LimitStencil()
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Far::LimitStencilTable
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~~~~~~~~~~~~~~~~~~~~~~
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- GetDuuWeights()
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- GetDuvWeights()
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- GetDvvWeights()
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- Update2ndDerivs()
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- extensions to LimitStencilTable()
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Far::LimitStencilTableFactory::Options
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- member generate1stDerivatives
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- member generate1stDerivatives
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- extensions to LimitTableStencilFactory::Create()
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Far::PatchParam
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~~~~~~~~~~~~~~~
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- IsRegular()
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- Unnormalize()
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- extensions to Set()
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Far::PatchTable
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~~~~~~~~~~~~~~~
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- ComputeLocalPointValuesFaceVarying()
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- ComputeLocalPointValuesVarying()
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- GetFVarPatchDescriptor()
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- GetFVarPatchParam()
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- GetNumLocalPointsFaceVarying()
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- GetNumLocalPointsVarying()
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- GetPatchArrayVaryingVertices()
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- GetPatchArrayFVarPatchParam()
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- GetPatchArrayFVarValues()
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- GetPatchFVarPatchParam()
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- GetPatchVaryingVertices()
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- GetVaryingPatchDescriptor()
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- GetVaryingVertices()
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- EvaluateBasisFaceVarying()
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- EvaluateBasisVarying()
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- extensions to EvaluateBasis()
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Far::PatchTableFactory::Options
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- member useInfSharpPatch
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- member genenerateFVarLegacyLinearPatches
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Far::TopologyLevel
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~~~~~~~~~~~~~~~~~~
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- DoesEdgeFVarTopologyMatch()
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- DoesFaceFVarTopologyMatch()
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- DoesVertexFVarTopologyMatch()
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- IsEdgeBoundary()
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- IsEdgeNonManifold()
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- IsVertexBoundary()
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- IsVertexNonManifold()
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Far::TopologyRefiner::AdaptiveOptions
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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- member secondaryLevel
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- member useInfSharpPatch
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- member considerFVarChannels
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Other Changes
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-------------
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Improvements
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~~~~~~~~~~~~
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- Enabled the use of CMake's folder feature
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- Removed the use of iso646 alternative keywords ('and', 'or', 'not', etc.) to improve portability
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- Added numerical valued preprocessor directives (OPENSUBDIV_VERSION_MAJOR, etc.) to <opensubdiv/version.h>
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- Improved documentation for Far::PatchParam and added Unnormalize() to complement Normalize()
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- Added additional topology queries to Far::TopologyLevel
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- Updated glFVarViewer and glEvalLimit viewer to make use of bicubic face-varying patches
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- Updated glViewer and dxViewer to add a toggle for InfSharpPatch
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- Updated dxPtexViewer for improved feature parity with glPtexViewer
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- Improved far_regression to exercise shapes independent of Hbr compatibility
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- Added support for Appveyor continuous integration testing
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- Removed cmake/FindIlmBase
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- Removed mayaPolySmooth example
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Bug Fixes
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~~~~~~~~~
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- Fixed Ptex version parsing and compatibility issues
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- Fixed compatibility issues with VS2015
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- Fixed bug interpolating face-varying data with Bilinear scheme
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- Fixed bug with refinement using Chaikin creasing
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- Fixed bugs with HUD sliders in the example viewers
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