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, 57 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/CCGSubSurf_intern.h b/source/blender/blenkernel/intern/CCGSubSurf_intern.h
index 1689ac482ef..d80bdcdb7fc 100644
--- a/source/blender/blenkernel/intern/CCGSubSurf_intern.h
+++ b/source/blender/blenkernel/intern/CCGSubSurf_intern.h
@@ -161,6 +161,9 @@ typedef enum {
 	eSyncState_Edge,
 	eSyncState_Face,
 	eSyncState_Partial,
+#ifdef WITH_OPENSUBDIV
+	eSyncState_OpenSubdiv,
+#endif
 } SyncState;
 
 struct CCGSubSurf {
@@ -203,6 +206,60 @@ struct CCGSubSurf {
 	int lenTempArrays;
 	CCGVert **tempVerts;
 	CCGEdge **tempEdges;
+
+#ifdef WITH_OPENSUBDIV
+	/* Skip grids means no CCG geometry is created and subsurf is possible
+	 * to be completely done on GPU.
+	 */
+	bool skip_grids;
+
+	/* ** GPU backend. ** */
+
+	/* Compute device used by GL mesh. */
+	short osd_compute;
+	/* Coarse (base mesh) vertex coordinates.
+	 *
+	 * Filled in from the modifier stack and passed to OpenSubdiv compute
+	 * on mesh display.
+	 */
+	float (*osd_coarse_coords)[3];
+	int osd_num_coarse_coords;
+	/* Denotes whether coarse positions in the GL mesh are invalid.
+	 * Used to avoid updating GL mesh coords on every redraw.
+	 */
+	bool osd_coarse_coords_invalid;
+
+	/* GL mesh descriptor, used for refinment and draw. */
+	struct OpenSubdiv_GLMesh *osd_mesh;
+	/* Refiner which is used to create GL mesh.
+	 *
+	 * Refiner is created from the modifier stack and used later from the main
+	 * thread to construct GL mesh to avoid threaded access to GL.
+	 */
+	struct OpenSubdiv_TopologyRefinerDescr *osd_topology_refiner;  /* Only used at synchronization stage. */
+	/* Denotes whether osd_mesh is invalid now due to topology changes and needs
+	 * to be reconstructed.
+	 *
+	 * Reconstruction happens from main thread due to OpenGL communication.
+	 */
+	bool osd_mesh_invalid;
+	/* Vertex array used for osd_mesh draw. */
+	unsigned int osd_vao;
+
+	/* ** CPU backend. ** */
+
+	/* Limit evaluator, used to evaluate CCG. */
+	struct OpenSubdiv_EvaluatorDescr *osd_evaluator;
+	/* Next PTex face index, used while CCG synchroization
+	 * to fill in PTex index of CCGFace.
+	 */
+	int osd_next_face_ptex_index;
+
+	/* ** Needs review.  ** */
+	bool osd_subsurf_uv;
+	int osd_uv_index;
+	bool osd_uvs_invalid;
+#endif
 };
 
 /* ** Utility macros ** */