diff --git a/documentation/CMakeLists.txt b/documentation/CMakeLists.txt index 71e7c6df..359e9e34 100644 --- a/documentation/CMakeLists.txt +++ b/documentation/CMakeLists.txt @@ -82,6 +82,7 @@ if (DOCUTILS_FOUND AND PYTHONINTERP_FOUND) hbr_overview.rst intro.rst license.rst + mod_notes.rst maya_osdpolysmooth.rst osd_overview.rst release_notes.rst diff --git a/documentation/images/crease_editor.png b/documentation/images/crease_editor.png new file mode 100644 index 00000000..810e25e0 Binary files /dev/null and b/documentation/images/crease_editor.png differ diff --git a/documentation/images/edge_loops.png b/documentation/images/edge_loops.png new file mode 100644 index 00000000..dff3b01f Binary files /dev/null and b/documentation/images/edge_loops.png differ diff --git a/documentation/images/mod_notes.0.png b/documentation/images/mod_notes.0.png new file mode 100644 index 00000000..c9bcd53b Binary files /dev/null and b/documentation/images/mod_notes.0.png differ diff --git a/documentation/images/mod_notes.1.png b/documentation/images/mod_notes.1.png new file mode 100644 index 00000000..d36b8c47 Binary files /dev/null and b/documentation/images/mod_notes.1.png differ diff --git a/documentation/images/mod_notes.2.png b/documentation/images/mod_notes.2.png new file mode 100644 index 00000000..271c9cc7 Binary files /dev/null and b/documentation/images/mod_notes.2.png differ diff --git a/documentation/images/mod_notes.3.png b/documentation/images/mod_notes.3.png new file mode 100644 index 00000000..d1c84612 Binary files /dev/null and b/documentation/images/mod_notes.3.png differ diff --git a/documentation/images/mod_notes.4.jpg b/documentation/images/mod_notes.4.jpg new file mode 100644 index 00000000..6a51a53b Binary files /dev/null and b/documentation/images/mod_notes.4.jpg differ diff --git a/documentation/images/mod_notes.5.png b/documentation/images/mod_notes.5.png new file mode 100644 index 00000000..92db167c Binary files /dev/null and b/documentation/images/mod_notes.5.png differ diff --git a/documentation/mod_notes.rst b/documentation/mod_notes.rst new file mode 100644 index 00000000..198669c0 --- /dev/null +++ b/documentation/mod_notes.rst @@ -0,0 +1,168 @@ +.. + 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. + + +Modeling Tips +------------- + +.. contents:: + :local: + :backlinks: none + +---- + +Well-constructed subdivision meshes have several important properties: + + * They consist primarily of quad faces + * They contain few extraordinary vertices + * They efficiently describe the intended shape + * They are topologically `manifold `__ + +The following sections describe common techniques specific to modeling with +subdivision surfaces. + +Use Fewer Spans +=============== + +While polygon models need to use a large number of spans to approximate smooth +curved surfaces, subdivision models require significantly fewer control points. + +In most situation, 6 spans is enough to create a circular shape and 4 is often +enough to approximate it for background objects. + +.. image:: images/mod_notes.0.png + :align: center + :target: images/mod_notes.0.png + +Avoid High Valence vertices +=========================== + +A high valence vertex is a vertex connected to more than 4 adjacent edges. + +High valence vertices cause several problems when subdivided: + + * OpenSubdiv has a hard constraint imposed by GPU shaders on the maximum + valence of a vertex (~27 on current hardware) + * High valence vertices incur fairly large performance hits + * The Catmull-Clark scheme can produce "wavy" surfaces when a revolution + vertex is surrounded by triangles (see `here `__): + + .. image:: images/mod_notes.2.png + :width: 200px + :align: center + :target: images/mod_notes.2.png + +Instead, here are some topological strategies to cap revolution shapes: + +.. image:: images/mod_notes.1.png + :align: center + :target: images/mod_notes.1.png + +Note that all these cylinders use only quad faces, and all the vertices in the +caps have a valence of 4 (except the bottom left example) + +Edge-Loop Transitions +===================== + +It is often necessary to vary the density of control vertices over the surface +mesh: areas around the fingers of a hand require more CVs than the comparitively +simpler region around the palm. It is important to handle the topology around +these transitions efficiently. + +One strategy is to use extraordinary vertices, such as this example using a +valence 5 vertex to expand 3 edge loops into 5. + +.. image:: images/edge_loops.png + :align: center + :width: 400px + :target: images/edge_loops.png + +As an alternatives to this pattern, it is possible to use triangles or pentagons +instead of extraordinary vertices. + +Practical Topology Primer +========================= + +Some real-world examples showing how to produce detailed shapes with sparse +topology, few extraordinary vertices, and no high-valence revolution poles. + +.. image:: images/mod_notes.3.png + :align: center + :target: images/mod_notes.3.png + +.. image:: images/mod_notes.4.jpg + :align: center + :target: images/mod_notes.4.jpg + +Triangles and N-Gons +==================== + +Used sparsely, non-quads can be very useful to gather 3 or more diverging +edge-loops. These are often encountered in highly deforming areas with curvature +saddle-points (ex: arm-torso connection). The strategic placement of a pentagon +in one of these critical spots ensures that the surface remains smooth, while +allowing for complex topology to flow around. + +.. image:: images/mod_notes.5.png + :align: center + :target: images/mod_notes.5.png + + +Semi-Sharp Creases +================== + +Semi-sharp creases can be a very powerful tool for hard-surface modeling. + + * Creases introduce extra computation costs proportional to the sharpness + value. However... + * It is generally cheaper to use creases whenever possible instead of adding + extra edges / edge loops. + * Crease sharpness ranges from 0 (smooth) to 10 (infinitely sharp) + * Sharpness above 5 should rarely be needed. + * Both edges and vertices can be tagged with a sharpness value. + +The following sections introduce some techniques to best leverage them. + +Use crease sets ++++++++++++++++ + +Complex hard-surface models (giant robots, vehicles, buildings...) are likely to +tag large number of edges : it is extremely useful to organize these edges/edge +loops into logical sets with descriptive names. Edges or vertices in a crease +set group all share the same sharpness value. If you are modeling with Maya, +the CreaseSetEditor implements this type of workflow. + +One of the benefits of having edge-loops share identical sharpness values is +that enables very powerful optimizations within the feature adaptive algorithm. + +.. image:: images/crease_editor.png + :align: center + :target: images/crease_editor.png + +Additionally, for debugging purposes, it is often very helpful if the name of a +set contains the sharpness value (ex: topDeck_2) + +.. include:: under_development.rst + + + diff --git a/documentation/nav_template.txt b/documentation/nav_template.txt index d55e3d86..64b4d35f 100644 --- a/documentation/nav_template.txt +++ b/documentation/nav_template.txt @@ -41,6 +41,9 @@
  • Roadmap

    • +
  • Modeling Tips +
    • +

  • Subdivision Surfaces
    • Introduction
      • @@ -69,7 +72,6 @@

    • Tutorials
    • Compiling & Linking
      • -
    • Writing Shaders
    • Textures

    • (Hbr)
      • diff --git a/documentation/roadmap.rst b/documentation/roadmap.rst index 72bbf27b..94e1bf4c 100644 --- a/documentation/roadmap.rst +++ b/documentation/roadmap.rst @@ -30,8 +30,6 @@ Roadmap ---- -.. include:: under_development.rst - 3.x Release Cycle =================