OpenSubdiv: Re-work C-API integration

Main goal is to make API simpler to follow (at least ion terms what
is defined/declared where, as opposite of handful big headers which
includes all the declarations), and also avoid a big set of long and
obscure functions.

Now C-API files are split into smaller ones, following OpenSubdiv
behavior more closely, and also function pointers in structures
used a lot more, which shortens functions names,

UV integration part in GL Mesh is mainly stripped away, it needs
to be done differently. On a related topic, UV coordinates API in
converter needs to be removed as well, we do not need coordinates,
only island connectivity information there.

Additional changes:

- Varying interpolation in evaluator API are temporarily disabled,
  need to extend API somewhere (probably, evaluator's API) to inform
  layout information of vertex data (whether it contains varying
  data, width, stride and such).

- Evaluator now can interpolate face-varying data.
  Only works for adaptive refiner, since some issues in OpenSubdiv
  itself.

Planned changes:

- Remove uv coordinates from TopologyConverter.
- Support evaluation of patches (as opposite to individual coordinates
  as it happens currently).
- Support more flexible layout of varying and face-varying data.
  It is stupid to assume varying is 3 floats and face-varying 2 floats.
- Support of second order derivatives.
- Everything else what i'm missing in this list.

1 files changed, 66 insertions, 0 deletions

diff --git a/intern/opensubdiv/internal/opensubdiv_converter_orient_impl.h b/intern/opensubdiv/internal/opensubdiv_converter_orient_impl.h
new file mode 100644
index 00000000000..3125bc600e5
--- /dev/null
+++ b/intern/opensubdiv/internal/opensubdiv_converter_orient_impl.h
@@ -0,0 +1,66 @@
+// Copyright 2018 Blender Foundation. All rights reserved.
+//
+// This program is free software; you can redistribute it and/or
+// modify it under the terms of the GNU General Public License
+// as published by the Free Software Foundation; either version 2
+// of the License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software Foundation,
+// Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+//
+// Author: Sergey Sharybin
+
+#ifndef OPENSUBDIV_CONVERTER_ORIENT_IMPL_H_
+#define OPENSUBDIV_CONVERTER_ORIENT_IMPL_H_
+
+#include "internal/opensubdiv_converter_orient.h"
+
+#include <algorithm>
+#include <cmath>
+#include <utility>
+
+namespace opensubdiv_capi {
+
+inline void reverseFaceVertices(int* face_vertices, const int num_vertices) {
+  int last_vert = face_vertices[num_vertices - 1];
+  for (int i = num_vertices - 1; i > 0; --i) {
+    face_vertices[i] = face_vertices[i - 1];
+  }
+  face_vertices[0] = last_vert;
+}
+
+inline int getLoopWinding(int vert0_of_face, int vert1_of_face) {
+  int delta_face = vert1_of_face - vert0_of_face;
+  if (abs(delta_face) != 1) {
+    if (delta_face > 0) {
+      delta_face = -1;
+    } else {
+      delta_face = 1;
+    }
+  }
+  return delta_face;
+}
+
+inline void reverseFaceLoops(
+    OpenSubdiv::Far::IndexArray* face_vertices,
+    OpenSubdiv::Far::IndexArray* face_edges) {
+  const int num_face_vertices = face_vertices->size();
+  for (int i = 0; i < num_face_vertices / 2; ++i) {
+    const int j = num_face_vertices - i - 1;
+    if (i != j) {
+      std::swap((*face_vertices)[i], (*face_vertices)[j]);
+      std::swap((*face_edges)[i], (*face_edges)[j]);
+    }
+  }
+  reverseFaceVertices(&(*face_vertices)[0], num_face_vertices);
+}
+
+}  // namespace opensubdiv_capi
+
+#endif  // OPENSUBDIV_CONVERTER_ORIENT_IMPL_H_