OpenSubdiv: Commit of OpenSubdiv integration into Blender

This commit contains all the remained parts needed for initial integration of
OpenSubdiv into Blender's subdivision surface code. Includes both GPU and CPU
backends which works in the following way:

- When SubSurf modifier is the last in the modifiers stack then GPU pipeline
  of OpenSubdiv is used, making viewport performance as fast as possible.

  This also requires graphscard with GLSL 1.5 support. If this requirement is
  not met, then no GPU pipeline is used at all.

- If SubSurf is not a last modifier or if DerivesMesh is being evaluated for
  rendering then CPU limit evaluation API from OpenSubdiv is used. This only
  replaces the legacy evaluation code from CCGSubSurf_legacy, but keeps CCG
  structures exactly the same as they used to be for ages now.

This integration is fully covered with ifdef and not enabled by default
because there are several TODOs to be solved first:

- Face varying data interpolation is not really cleanly implemented for GPU
  in OpenSubdiv 3.0. It is also not implemented for limit evaluation API.

  This basically means we'll have really hard time supporting UVs.

- Limit evaluation only works with adaptivly subdivided meshes so far, which
  basically means all the points of CCG are pushed to the limit. This gives
  different result from old code.

- There are some serious optimizations possible on the topology refiner
  creation, which would speed up initial OpenSubdiv mesh creation.

- There are some hardcoded asumptions in the GPU and DerivedMesh areas which
  could be generalized.

  That's something where Antony and Campbell can help, making it so the code
  is structured in a way which is reusable by all planned viewport projects.

- There are also some workarounds in the dependency graph to make sure OpenGL
  buffers are only freed from the main thread.

Those who'll be wanting to make experiments with this code should grab dev
branch (NOT master) from

  https://github.com/Nazg-Gul/OpenSubdiv/tree/dev

There are some patches applied in there which we're working on on getting
into upstream.

1 files changed, 46 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/CCGSubSurf.h b/source/blender/blenkernel/intern/CCGSubSurf.h
index 2b86a2a66b2..23f7e71a311 100644
--- a/source/blender/blenkernel/intern/CCGSubSurf.h
+++ b/source/blender/blenkernel/intern/CCGSubSurf.h
@@ -80,6 +80,9 @@ void		ccgSubSurf_free	(CCGSubSurf *ss);
 
 CCGError	ccgSubSurf_initFullSync		(CCGSubSurf *ss);
 CCGError	ccgSubSurf_initPartialSync	(CCGSubSurf *ss);
+#ifdef WITH_OPENSUBDIV
+CCGError	ccgSubSurf_initOpenSubdivSync	(CCGSubSurf *ss);
+#endif
 
 CCGError	ccgSubSurf_syncVert		(CCGSubSurf *ss, CCGVertHDL vHDL, const void *vertData, int seam, CCGVert **v_r);
 CCGError	ccgSubSurf_syncEdge		(CCGSubSurf *ss, CCGEdgeHDL eHDL, CCGVertHDL e_vHDL0, CCGVertHDL e_vHDL1, float crease, CCGEdge **e_r);
@@ -190,4 +193,47 @@ CCGFace*			ccgFaceIterator_getCurrent	(CCGFaceIterator *fi);
 int					ccgFaceIterator_isStopped	(CCGFaceIterator *fi);
 void				ccgFaceIterator_next		(CCGFaceIterator *fi);
 
+#ifdef WITH_OPENSUBDIV
+struct DerivedMesh;
+
+/* Check if topology changed and evaluators are to be re-created. */
+void ccgSubSurf_checkTopologyChanged(CCGSubSurf *ss, struct DerivedMesh *dm);
+
+/* Create topology refiner from give derived mesh which then later will be
+ * used for GL mesh creation.
+ */
+void ccgSubSurf_prepareTopologyRefiner(CCGSubSurf *ss, struct DerivedMesh *dm);
+
+/* Make sure GL mesh exists, up to date and ready to draw. */
+bool ccgSubSurf_prepareGLMesh(CCGSubSurf *ss, bool use_osd_glsl);
+
+/* Draw given partitions of the GL mesh.
+ *
+ * TODO(sergey): fill_quads is actually an invariant and should be part
+ * of the prepare routine.
+ */
+void ccgSubSurf_drawGLMesh(CCGSubSurf *ss, bool fill_quads,
+                           int start_partition, int num_partitions);
+
+/* Controls whether CCG are needed (Cmeaning CPU evaluation) or fully GPU compute
+ * and draw is allowed.
+ */
+void ccgSubSurf_setSkipGrids(CCGSubSurf *ss, bool skip_grids);
+bool ccgSubSurf_needGrids(CCGSubSurf *ss);
+
+/* Set evaluator's face varying data from UV coordinates.
+ * Used for CPU evaluation.
+ */
+void ccgSubSurf_evaluatorSetFVarUV(CCGSubSurf *ss,
+                                   struct DerivedMesh *dm,
+                                   int layer_index);
+
+/* TODO(sergey): Temporary call to test things. */
+void ccgSubSurf_evaluatorFVarUV(CCGSubSurf *ss,
+                                int face_index, int S,
+                                float grid_u, float grid_v,
+                                float uv[2]);
+
+#endif
+
 #endif  /* __CCGSUBSURF_H__ */