Split Normals I (2/5): Add basic BMesh support of split normals.

* Merely a re-implementation of core split algorithm for BMesh, taking advantage of topological data available.
* This code needs valid loop indices, so added BM_LOOP support to BM_mesh_elem_index_ensure() & co.

Reviewers: campbellbarton

Reviewed By: campbellbarton

CC: brecht

Differential Revision: https://developer.blender.org/D366

source/blender/blenkernel/intern/editderivedmesh.c

@@ -173,7 +173,26 @@ static void emDM_calcNormals(DerivedMesh *dm)
 
 static void emDM_calcLoopNormals(DerivedMesh *dm, const float split_angle)
 {
-	/* Do nothing for now! */
+	EditDerivedBMesh *bmdm = (EditDerivedBMesh *)dm;
+	BMesh *bm = bmdm->em->bm;
+	const float (*vertexCos)[3], (*vertexNos)[3], (*polyNos)[3];
+	float (*loopNos)[3];
+
+	/* calculate loop normals from poly and vertex normals */
+	emDM_ensureVertNormals(bmdm);
+	dm->dirty &= ~DM_DIRTY_NORMALS;
+
+	vertexCos = bmdm->vertexCos;
+	vertexNos = bmdm->vertexNos;
+	polyNos = bmdm->polyNos;
+
+	loopNos = dm->getLoopDataArray(dm, CD_NORMAL);
+	if (!loopNos) {
+		DM_add_loop_layer(dm, CD_NORMAL, CD_CALLOC, NULL);
+		loopNos = dm->getLoopDataArray(dm, CD_NORMAL);
+	}
+
+	BM_loops_calc_normal_vcos(bm, vertexCos, vertexNos, polyNos, split_angle, loopNos);
 }
 
 static void emDM_recalcTessellation(DerivedMesh *UNUSED(dm))
@@ -1530,6 +1549,31 @@ static void *emDM_getTessFaceDataArray(DerivedMesh *dm, int type)
 		}
 	}
 
+	/* Special handling for CD_TESSLOOPNORMAL, we generate it on demand as well. */
+	if (type == CD_TESSLOOPNORMAL) {
+		const float (*lnors)[3] = dm->getLoopDataArray(dm, CD_NORMAL);
+
+		if (lnors) {
+			BMLoop *(*looptris)[3] = bmdm->em->looptris;
+			short (*tlnors)[4][3], (*tlnor)[4][3];
+			int index, i, j;
+
+			DM_add_tessface_layer(dm, type, CD_CALLOC, NULL);
+			index = CustomData_get_layer_index(&dm->faceData, type);
+			dm->faceData.layers[index].flag |= CD_FLAG_TEMPORARY;
+
+			tlnor = tlnors = DM_get_tessface_data_layer(dm, type);
+
+			BM_mesh_elem_index_ensure(bm, BM_LOOP);
+
+			for (i = 0; i < bmdm->em->tottri; i++, tlnor++, looptris++) {
+				for (j = 0; j < 3; j++) {
+					normal_float_to_short_v3((*tlnor)[j], lnors[BM_elem_index_get((*looptris)[j])]);
+				}
+			}
+		}
+	}
+
 	return datalayer;
 }
 

source/blender/bmesh/bmesh_class.h

@@ -66,7 +66,7 @@ typedef struct BMHeader {
 	int index; /* notes:
 	            * - Use BM_elem_index_get/set macros for index
 	            * - Uninitialized to -1 so we can easily tell its not set.
-	            * - Used for edge/vert/face, check BMesh.elem_index_dirty for valid index values,
+	            * - Used for edge/vert/face/loop, check BMesh.elem_index_dirty for valid index values,
 	            *   this is abused by various tools which set it dirty.
 	            * - For loops this is used for sorting during tessellation. */
 
@@ -188,9 +188,8 @@ typedef struct BMesh {
 	int totvertsel, totedgesel, totfacesel;
 
 	/* flag index arrays as being dirty so we can check if they are clean and
-	 * avoid looping over the entire vert/edge/face array in those cases.
-	 * valid flags are - BM_VERT | BM_EDGE | BM_FACE.
-	 * BM_LOOP isn't handled so far. */
+	 * avoid looping over the entire vert/edge/face/loop array in those cases.
+	 * valid flags are - BM_VERT | BM_EDGE | BM_FACE | BM_LOOP. */
 	char elem_index_dirty;
 
 	/* flag array table as being dirty so we know when its safe to use it,

source/blender/bmesh/intern/bmesh_core.c

@@ -211,6 +211,8 @@ static BMLoop *bm_loop_create(BMesh *bm, BMVert *v, BMEdge *e, BMFace *f,
 	l->prev = NULL;
 	/* --- done --- */
 
+	/* may add to middle of the pool */
+	bm->elem_index_dirty |= BM_LOOP;
 
 	bm->totloop++;
 

source/blender/bmesh/intern/bmesh_mesh.c

@@ -31,6 +31,7 @@
 #include "DNA_listBase.h"
 #include "DNA_object_types.h"
 
+#include "BLI_linklist_stack.h"
 #include "BLI_listbase.h"
 #include "BLI_math.h"
 #include "BLI_utildefines.h"
@@ -431,6 +432,230 @@ void BM_verts_calc_normal_vcos(BMesh *bm, const float (*fnos)[3], const float (*
 	MEM_freeN(edgevec);
 }
 
+/**
+ * Helpers for #BM_mesh_loop_normals_update and #BM_loops_calc_normals_vnos
+ */
+static void bm_mesh_edges_sharp_tag(BMesh *bm, const float (*vnos)[3], const float (*fnos)[3], float split_angle,
+                                    float (*r_lnos)[3])
+{
+	BMIter eiter;
+	BMEdge *e;
+	int i;
+
+	const bool check_angle = (split_angle < (float)M_PI);
+
+	if (check_angle) {
+		split_angle = cosf(split_angle);
+	}
+
+	{
+		char hflag = BM_LOOP;
+		if (vnos)
+			hflag |= BM_VERT;
+		if (fnos)
+			hflag |= BM_FACE;
+		BM_mesh_elem_index_ensure(bm, hflag);
+	}
+
+	/* This first loop checks which edges are actually smooth, and pre-populate lnos with vnos (as if they were
+	 * all smooth).
+	 */
+	BM_ITER_MESH_INDEX (e, &eiter, bm, BM_EDGES_OF_MESH, i) {
+		BMLoop *l_a, *l_b;
+
+		BM_elem_index_set(e, i); /* set_inline */
+		BM_elem_flag_disable(e, BM_ELEM_TAG); /* Clear tag (means edge is sharp). */
+
+		/* An edge with only two loops, might be smooth... */
+		if (BM_edge_loop_pair(e, &l_a, &l_b)) {
+			bool is_angle_smooth = true;
+			if (check_angle) {
+				const float *no_a = fnos ? fnos[BM_elem_index_get(l_b->f)] : l_a->f->no;
+				const float *no_b = fnos ? fnos[BM_elem_index_get(l_b->f)] : l_b->f->no;
+				is_angle_smooth = (dot_v3v3(no_a, no_b) >= split_angle);
+			}
+
+			/* We only tag edges that are *really* smooth... */
+			if (is_angle_smooth &&
+			    BM_elem_flag_test_bool(e, BM_ELEM_SMOOTH) &&
+			    BM_elem_flag_test_bool(l_a->f, BM_ELEM_SMOOTH) &&
+			    BM_elem_flag_test_bool(l_b->f, BM_ELEM_SMOOTH))
+			{
+				const float *no;
+				BM_elem_flag_enable(e, BM_ELEM_TAG);
+
+				/* linked vertices might be fully smooth, copy their normals to loop ones. */
+				no = vnos ? vnos[BM_elem_index_get(l_a->v)] : l_a->v->no;
+				copy_v3_v3(r_lnos[BM_elem_index_get(l_a)], no);
+				no = vnos ? vnos[BM_elem_index_get(l_b->v)] : l_b->v->no;
+				copy_v3_v3(r_lnos[BM_elem_index_get(l_b)], no);
+			}
+		}
+	}
+
+	bm->elem_index_dirty &= ~BM_EDGE;
+}
+
+/* BMesh version of BKE_mesh_normals_loop_split() in mesh_evaluate.c */
+static void bm_mesh_loops_calc_normals(BMesh *bm, const float (*vcos)[3], const float (*fnos)[3], float (*r_lnos)[3])
+{
+	BMIter fiter;
+	BMFace *f_curr;
+
+	/* Temp normal stack. */
+	BLI_SMALLSTACK_DECLARE(normal, float *);
+
+	{
+		char hflag = BM_LOOP;
+		if (vcos)
+			hflag |= BM_VERT;
+		if (fnos)
+			hflag |= BM_FACE;
+		BM_mesh_elem_index_ensure(bm, hflag);
+	}
+
+	/* We now know edges that can be smoothed (they are tagged), and edges that will be hard (they aren't).
+	 * Now, time to generate the normals.
+	 */
+	BM_ITER_MESH (f_curr, &fiter, bm, BM_FACES_OF_MESH) {
+		BMLoop *l_curr, *l_first;
+
+		l_curr = l_first = BM_FACE_FIRST_LOOP(f_curr);
+		do {
+			if (BM_elem_flag_test_bool(l_curr->e, BM_ELEM_TAG)) {
+				/* A smooth edge.
+				 * We skip it because it is either:
+				 * - in the middle of a 'smooth fan' already computed (or that will be as soon as we hit
+				 *   one of its ends, i.e. one of its two sharp edges), or...
+				 * - the related vertex is a "full smooth" one, in which case pre-populated normals from vertex
+				 *   are just fine!
+				 */
+			}
+			else if (!BM_elem_flag_test_bool(l_curr->prev->e, BM_ELEM_TAG)) {
+				/* Simple case (both edges around that vertex are sharp in related polygon),
+				 * this vertex just takes its poly normal.
+				 */
+				const float *no = fnos ? fnos[BM_elem_index_get(f_curr)] : f_curr->no;
+				copy_v3_v3(r_lnos[BM_elem_index_get(l_curr)], no);
+			}
+			else {
+				/* We have to fan around current vertex, until we find the other non-smooth edge,
+				 * and accumulate face normals into the vertex!
+				 * Note in case this vertex has only one sharp edge, this is a waste because the normal is the same as
+				 * the vertex normal, but I do not see any easy way to detect that (would need to count number
+				 * of sharp edges per vertex, I doubt the additional memory usage would be worth it, especially as
+				 * it should not be a common case in real-life meshes anyway).
+				 */
+				BMVert *v_pivot = l_curr->v;
+				BMEdge *e_next;
+				BMLoop *lfan_pivot, *lfan_pivot_next;
+				float lnor[3] = {0.0f, 0.0f, 0.0f};
+				float vec_curr[3], vec_next[3];
+
+				const float *co_pivot = vcos ? vcos[BM_elem_index_get(v_pivot)] : v_pivot->co;
+
+				lfan_pivot = l_curr;
+				e_next = lfan_pivot->e;  /* Current edge here, actually! */
+
+				/* Only need to compute previous edge's vector once, then we can just reuse old current one! */
+				{
+					const BMVert *v_2 = BM_edge_other_vert(e_next, v_pivot);
+					const float *co_2 = vcos ? vcos[BM_elem_index_get(v_2)] : v_2->co;
+
+					sub_v3_v3v3(vec_curr, co_2, co_pivot);
+					normalize_v3(vec_curr);
+				}
+
+				while (true) {
+					/* Much simpler than in sibling code with basic Mesh data! */
+					lfan_pivot_next = BM_vert_step_fan_loop(lfan_pivot, &e_next);
+					BLI_assert(lfan_pivot_next->v == v_pivot);
+
+					/* Compute edge vector.
+					 * NOTE: We could pre-compute those into an array, in the first iteration, instead of computing them
+					 *       twice (or more) here. However, time gained is not worth memory and time lost,
+					 *       given the fact that this code should not be called that much in real-life meshes...
+					 */
+					{
+						const BMVert *v_2 = BM_edge_other_vert(e_next, v_pivot);
+						const float *co_2 = vcos ? vcos[BM_elem_index_get(v_2)] : v_2->co;
+
+						sub_v3_v3v3(vec_next, co_2, co_pivot);
+						normalize_v3(vec_next);
+					}
+
+					{
+						/* Code similar to accumulate_vertex_normals_poly. */
+						/* Calculate angle between the two poly edges incident on this vertex. */
+						const BMFace *f = lfan_pivot->f;
+						const float fac = saacos(dot_v3v3(vec_next, vec_curr));
+						const float *no = fnos ? fnos[BM_elem_index_get(f)] : f->no;
+						/* Accumulate */
+						madd_v3_v3fl(lnor, no, fac);
+					}
+
+					/* We store here a pointer to all loop-normals processed. */
+					BLI_SMALLSTACK_PUSH(normal, (float *)r_lnos[BM_elem_index_get(lfan_pivot)]);
+
+					if (!BM_elem_flag_test_bool(e_next, BM_ELEM_TAG)) {
+						/* Next edge is sharp, we have finished with this fan of faces around this vert! */
+						break;
+					}
+
+					/* Copy next edge vector to current one. */
+					copy_v3_v3(vec_curr, vec_next);
+					/* Next pivot loop to current one. */
+					lfan_pivot = lfan_pivot_next;
+				}
+
+				/* In case we get a zero normal here, just use vertex normal already set! */
+				if (LIKELY(normalize_v3(lnor) != 0.0f)) {
+					/* Copy back the final computed normal into all related loop-normals. */
+					float *nor;
+					while ((nor = BLI_SMALLSTACK_POP(normal))) {
+						copy_v3_v3(nor, lnor);
+					}
+				}
+			}
+		} while ((l_curr = l_curr->next) != l_first);
+	}
+
+	BLI_SMALLSTACK_FREE(normal);
+}
+
+#if 0  /* Unused currently */
+/**
+ * \brief BMesh Compute Loop Normals
+ *
+ * Updates the loop normals of a mesh. Assumes vertex and face normals are valid (else call BM_mesh_normals_update()
+ * first)!
+ */
+void BM_mesh_loop_normals_update(BMesh *bm, const float split_angle, float (*r_lnos)[3])
+{
+	/* Tag smooth edges and set lnos from vnos when they might be completely smooth... */
+	bm_mesh_edges_sharp_tag(bm, NULL, NULL, split_angle, r_lnos);
+
+	/* Finish computing lnos by accumulating face normals in each fan of faces defined by sharp edges. */
+	bm_mesh_loops_calc_normals(bm, NULL, NULL, r_lnos);
+}
+#endif
+
+/**
+ * \brief BMesh Compute Loop Normals from/to external data.
+ *
+ * Compute split normals, i.e. vertex normals associated with each poly (hence 'loop normals').
+ * Useful to materialize sharp edges (or non-smooth faces) without actually modifying the geometry (splitting edges).
+ */
+void BM_loops_calc_normal_vcos(BMesh *bm, const float (*vcos)[3], const float (*vnos)[3], const float (*fnos)[3],
+                                const float split_angle, float (*r_lnos)[3])
+{
+	/* Tag smooth edges and set lnos from vnos when they might be completely smooth... */
+	bm_mesh_edges_sharp_tag(bm, vnos, fnos, split_angle, r_lnos);
+
+	/* Finish computing lnos by accumulating face normals in each fan of faces defined by sharp edges. */
+	bm_mesh_loops_calc_normals(bm, vcos, fnos, r_lnos);
+}
+
 static void UNUSED_FUNCTION(bm_mdisps_space_set)(Object *ob, BMesh *bm, int from, int to)
 {
 	/* switch multires data out of tangent space */
@@ -585,19 +810,35 @@ void BM_mesh_elem_index_ensure(BMesh *bm, const char hflag)
 
 #pragma omp section
 		{
-			if (hflag & BM_FACE) {
-				if (bm->elem_index_dirty & BM_FACE) {
+			if (hflag & (BM_FACE | BM_LOOP)) {
+				if (bm->elem_index_dirty & (BM_FACE | BM_LOOP)) {
 					BMIter iter;
 					BMElem *ele;
 
+					const bool hflag_loop = (hflag & BM_LOOP) && (bm->elem_index_dirty & BM_LOOP);
+
 					int index;
+					int index_loop_start = 0;
 					BM_ITER_MESH_INDEX (ele, &iter, bm, BM_FACES_OF_MESH, index) {
 						BM_elem_index_set(ele, index); /* set_ok */
+
+						if (hflag_loop) {
+							BMIter liter;
+							BMElem *lele;
+
+							int index_diff;
+							BM_ITER_ELEM_INDEX (lele, &liter, ele, BM_LOOPS_OF_FACE, index_diff) {
+								BM_elem_index_set(lele, index_loop_start + index_diff); /* set_ok */
+							}
+							index_loop_start += index_diff;
+						}
 					}
 					BLI_assert(index == bm->totface);
+					if (hflag & BM_LOOP)
+						BLI_assert(index_loop_start == bm->totloop);
 				}
 				else {
-					// printf("%s: skipping face index calc!\n", __func__);
+					// printf("%s: skipping face/loop index calc!\n", __func__);
 				}
 			}
 		}
@@ -1006,7 +1247,7 @@ void BM_mesh_remap(BMesh *bm, unsigned int *vert_idx, unsigned int *edge_idx, un
 			BLI_ghash_insert(fptr_map, (void *)*fap, (void *)new_fap);
 		}
 
-		bm->elem_index_dirty |= BM_FACE;
+		bm->elem_index_dirty |= BM_FACE | BM_LOOP;
 
 		MEM_freeN(faces_pool);
 		MEM_freeN(faces_copy);

source/blender/bmesh/intern/bmesh_mesh.h

@@ -39,6 +39,8 @@ void   BM_mesh_clear(BMesh *bm);
 
 void BM_mesh_normals_update(BMesh *bm);
 void BM_verts_calc_normal_vcos(BMesh *bm, const float (*fnos)[3], const float (*vcos)[3], float (*vnos)[3]);
+void BM_loops_calc_normal_vcos(BMesh *bm, const float (*vcos)[3], const float (*vnos)[3], const float (*pnos)[3],
+                               const float split_angle, float (*r_lnos)[3]);
 
 void bmesh_edit_begin(BMesh *bm, const BMOpTypeFlag type_flag);
 void bmesh_edit_end(BMesh *bm, const BMOpTypeFlag type_flag);

source/blender/bmesh/intern/bmesh_mesh_conv.c

@@ -441,6 +441,7 @@ void BM_mesh_bm_from_me(BMesh *bm, Mesh *me,
 	}
 
 	bm->elem_index_dirty &= ~BM_FACE; /* added in order, clear dirty flag */
+	bm->elem_index_dirty |= BM_LOOP; /* did not set the loop indices */
 
 	if (me->mselect && me->totselect != 0) {
 

source/blender/bmesh/tools/bmesh_decimate_collapse.c

@@ -1006,7 +1006,7 @@ void BM_mesh_decimate_collapse(BMesh *bm, const float factor, float *vweights, c
 	bm_decim_build_edge_cost(bm, vquadrics, vweights, eheap, eheap_table);
 
 	face_tot_target = bm->totface * factor;
-	bm->elem_index_dirty |= BM_FACE | BM_EDGE | BM_VERT;
+	bm->elem_index_dirty |= BM_FACE | BM_LOOP | BM_EDGE | BM_VERT;
 
 
 #ifdef USE_CUSTOMDATA

source/blender/bmesh/tools/bmesh_edgenet.c

@@ -500,7 +500,7 @@ void BM_mesh_edgenet(BMesh *bm,
 		BLI_assert(BLI_mempool_count(path_pool) == 0);
 	}
 
-	bm->elem_index_dirty |= BM_FACE;
+	bm->elem_index_dirty |= BM_FACE | BM_LOOP;
 
 	BLI_mempool_destroy(edge_queue_pool);
 	BLI_mempool_destroy(path_pool);

source/blender/modifiers/intern/MOD_array.c

@@ -191,7 +191,7 @@ static int *find_doubles_index_map(BMesh *bm, BMOperator *dupe_op,
 	}
 	/* above loops over all, so set all to dirty, if this is somehow
 	 * setting valid values, this line can be removed - campbell */
-	bm->elem_index_dirty |= BM_VERT | BM_EDGE | BM_FACE;
+	bm->elem_index_dirty |= BM_ALL;
 
 	(*index_map_length) = i;
 	index_map = MEM_callocN(sizeof(int) * (*index_map_length), "index_map");

source/blender/python/bmesh/bmesh_py_types.c

@@ -176,9 +176,7 @@ static int bpy_bm_elem_index_set(BPy_BMElem *self, PyObject *value, void *UNUSED
 		BM_elem_index_set(self->ele, param); /* set_dirty! */
 
 		/* when setting the index assume its set invalid */
-		if (self->ele->head.htype & (BM_VERT | BM_EDGE | BM_FACE)) {
-			self->bm->elem_index_dirty |= self->ele->head.htype;
-		}
+		self->bm->elem_index_dirty |= self->ele->head.htype;
 
 		return 0;
 	}
@@ -2264,11 +2262,9 @@ static PyObject *bpy_bmelemseq_index_update(BPy_BMElemSeq *self)
 				index++;
 			}
 
-			if (htype & (BM_VERT | BM_EDGE | BM_FACE)) {
-				/* since this isn't the normal vert/edge/face loops,
-				 * we're setting dirty values here. so tag as dirty. */
-				bm->elem_index_dirty |= htype;
-			}
+			/* since this isn't the normal vert/edge/face loops,
+			 * we're setting dirty values here. so tag as dirty. */
+			bm->elem_index_dirty |= htype;
 
 			break;
 		}