Add tessellation data to DerivedMesh (LoopTri)

This stores loop indices into the loop array giving easier acess
to data such as vertex-colors and UV's,
removing the need to store an MFace duplicate of custom-data.

This doesn't yet move all internal code from MFace to LoopTri just yet.

Only applies to:
- opengl drawing
- sculpting (pbvh)
- vertex/weight paint

Thanks to @psy-fi for review, fixes and improvements to drawing!

1 files changed, 44 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/editderivedmesh.c b/source/blender/blenkernel/intern/editderivedmesh.c
index 58f25179c5c..b8fade6e4cd 100644
--- a/source/blender/blenkernel/intern/editderivedmesh.c
+++ b/source/blender/blenkernel/intern/editderivedmesh.c
@@ -242,6 +242,47 @@ static void emDM_recalcTessellation(DerivedMesh *UNUSED(dm))
 	/* do nothing */
 }
 
+static void emDM_recalcLoopTri(DerivedMesh *UNUSED(dm))
+{
+	/* Nothing to do: emDM tessellation is known,
+	 * allocate and fill in with emDM_getLoopTriArray */
+}
+
+static const MLoopTri *emDM_getLoopTriArray(DerivedMesh *dm)
+{
+	if (dm->looptris.array) {
+		BLI_assert(poly_to_tri_count(dm->numPolyData, dm->numLoopData) == dm->looptris.num);
+	}
+	else {
+		EditDerivedBMesh *bmdm = (EditDerivedBMesh *)dm;
+		BMLoop *(*looptris)[3] = bmdm->em->looptris;
+		MLoopTri *mlooptri;
+		const int tottri = bmdm->em->tottri;
+		int i;
+
+		DM_ensure_looptri_data(dm);
+		mlooptri = dm->looptris.array;
+
+		BLI_assert(poly_to_tri_count(dm->numPolyData, dm->numLoopData) == dm->looptris.num);
+		BLI_assert(tottri == dm->looptris.num);
+
+		BM_mesh_elem_index_ensure(bmdm->em->bm, BM_FACE | BM_LOOP);
+
+		for (i = 0; i < tottri; i++) {
+			BMLoop **ltri = looptris[i];
+			MLoopTri *lt = &mlooptri[i];
+
+			ARRAY_SET_ITEMS(
+			        lt->tri,
+			        BM_elem_index_get(ltri[0]),
+			        BM_elem_index_get(ltri[1]),
+			        BM_elem_index_get(ltri[2]));
+			lt->poly = BM_elem_index_get(ltri[0]->f);
+		}
+	}
+	return dm->looptris.array;
+}
+
 static void emDM_foreachMappedVert(
         DerivedMesh *dm,
         void (*func)(void *userData, int index, const float co[3], const float no_f[3], const short no_s[3]),
@@ -1794,6 +1835,8 @@ DerivedMesh *getEditDerivedBMesh(BMEditMesh *em,
 	bmdm->dm.getNumLoops = emDM_getNumLoops;
 	bmdm->dm.getNumPolys = emDM_getNumPolys;
 
+	bmdm->dm.getLoopTriArray = emDM_getLoopTriArray;
+
 	bmdm->dm.getVert = emDM_getVert;
 	bmdm->dm.getVertCo = emDM_getVertCo;
 	bmdm->dm.getVertNo = emDM_getVertNo;
@@ -1812,6 +1855,7 @@ DerivedMesh *getEditDerivedBMesh(BMEditMesh *em,
 	bmdm->dm.calcLoopNormals = emDM_calcLoopNormals;
 	bmdm->dm.calcLoopNormalsSpaceArray = emDM_calcLoopNormalsSpaceArray;
 	bmdm->dm.recalcTessellation = emDM_recalcTessellation;
+	bmdm->dm.recalcLoopTri = emDM_recalcLoopTri;
 
 	bmdm->dm.foreachMappedVert = emDM_foreachMappedVert;
 	bmdm->dm.foreachMappedLoop = emDM_foreachMappedLoop;