[Bf-blender-cvs] [d5be72b] alembic: Nicer iterator for looping over strand edges directly.

[Lukas Tönne]

Commit: d5be72b05f6be3e0a7d126d7f43bef386d532811
Author: Lukas Tönne
Date:   Tue Apr 7 18:12:04 2015 +0200
Branches: alembic
https://developer.blender.org/rBd5be72b05f6be3e0a7d126d7f43bef386d532811

Nicer iterator for looping over strand edges directly.

Avoids the ugly construct with vertex iterators that have to drag an
extra 'prev' iterator along.

===================================================================

M	source/blender/blenkernel/BKE_strands.h
M	source/blender/physics/intern/BPH_mass_spring.cpp

===================================================================

diff --git a/source/blender/blenkernel/BKE_strands.h b/source/blender/blenkernel/BKE_strands.h
index 1ce3c57..7462e18 100644
--- a/source/blender/blenkernel/BKE_strands.h
+++ b/source/blender/blenkernel/BKE_strands.h
@@ -140,4 +140,47 @@ BLI_INLINE size_t BKE_strand_vertex_iter_vertex_offset(Strands *strands, StrandV
 	return iter->vertex - strands->verts;
 }
 
+
+typedef struct StrandEdgeIterator {
+	int index, tot;
+	StrandsVertex *vertex0, *vertex1;
+	StrandsMotionState *state0, *state1;
+} StrandEdgeIterator;
+
+BLI_INLINE void BKE_strand_edge_iter_init(StrandEdgeIterator *iter, StrandIterator *strand_iter)
+{
+	iter->tot = strand_iter->curve->numverts - 1;
+	iter->index = 0;
+	iter->vertex0 = strand_iter->verts;
+	iter->state0 = strand_iter->state;
+	iter->vertex1 = strand_iter->verts + 1;
+	iter->state1 = strand_iter->state + 1;
+}
+
+BLI_INLINE bool BKE_strand_edge_iter_valid(StrandEdgeIterator *iter)
+{
+	return iter->index < iter->tot;
+}
+
+BLI_INLINE void BKE_strand_edge_iter_next(StrandEdgeIterator *iter)
+{
+	++iter->vertex0;
+	++iter->vertex1;
+	if (iter->state0) {
+		++iter->state0;
+		++iter->state1;
+	}
+	++iter->index;
+}
+
+BLI_INLINE size_t BKE_strand_edge_iter_vertex0_offset(Strands *strands, StrandEdgeIterator *iter)
+{
+	return iter->vertex0 - strands->verts;
+}
+
+BLI_INLINE size_t BKE_strand_edge_iter_vertex1_offset(Strands *strands, StrandEdgeIterator *iter)
+{
+	return iter->vertex1 - strands->verts;
+}
+
 #endif  /* __BKE_STRANDS_H__ */
diff --git a/source/blender/physics/intern/BPH_mass_spring.cpp b/source/blender/physics/intern/BPH_mass_spring.cpp
index 53f3718..5c1aa6c 100644
--- a/source/blender/physics/intern/BPH_mass_spring.cpp
+++ b/source/blender/physics/intern/BPH_mass_spring.cpp
@@ -1197,6 +1197,28 @@ static void strands_setup_constraints(Strands *strands, Implicit_Data *data, Col
 #endif
 }
 
+/* calculates internal forces for a single strand curve */
+static void strands_calc_curve_stretch_forces(Strands *strands, HairSimParams *params, Implicit_Data *data, StrandIterator *it_strand)
+{
+	StrandEdgeIterator it_edge;
+	
+	for (BKE_strand_edge_iter_init(&it_edge, it_strand); BKE_strand_edge_iter_valid(&it_edge); BKE_strand_edge_iter_next(&it_edge)) {
+		int vi = BKE_strand_edge_iter_vertex0_offset(strands, &it_edge);
+		int vj = BKE_strand_edge_iter_vertex1_offset(strands, &it_edge);
+		float restlen = len_v3v3(it_edge.vertex0->co, it_edge.vertex1->co);
+		
+		float stiffness = params->stretch_stiffness;
+		float damping = stiffness * params->stretch_damping;
+		BPH_mass_spring_force_spring_linear(data, vi, vj, restlen, stiffness, damping, true, 0.0f, NULL, NULL, NULL);
+	}
+}
+
+/* calculates internal forces for a single strand curve */
+static void strands_calc_curve_forces(Strands *strands, HairSimParams *params, Implicit_Data *data, StrandIterator *it_strand)
+{
+	strands_calc_curve_stretch_forces(strands, params, data, it_strand);
+}
+
 /* Collect forces and derivatives:  F, dFdX, dFdV */
 static void strands_calc_force(Strands *strands, HairSimParams *params, Implicit_Data *data, float UNUSED(frame), Scene *scene, ListBase *effectors)
 {
@@ -1258,22 +1280,7 @@ static void strands_calc_force(Strands *strands, HairSimParams *params, Implicit
 	/* spring forces */
 	StrandIterator it_strand;
 	for (BKE_strand_iter_init(&it_strand, strands); BKE_strand_iter_valid(&it_strand); BKE_strand_iter_next(&it_strand)) {
-		StrandVertexIterator it_vert, it_vert_prev;
-		BKE_strand_vertex_iter_init(&it_vert, &it_strand);
-		if (BKE_strand_vertex_iter_valid(&it_vert)) {
-			it_vert_prev = it_vert;
-			BKE_strand_vertex_iter_next(&it_vert);
-			for (; BKE_strand_vertex_iter_valid(&it_vert); it_vert_prev = it_vert, BKE_strand_vertex_iter_next(&it_vert)) {
-				
-				int vi = BKE_strand_vertex_iter_vertex_offset(strands, &it_vert);
-				int vj = BKE_strand_vertex_iter_vertex_offset(strands, &it_vert_prev);
-				float restlen = len_v3v3(it_vert.vertex->co, it_vert_prev.vertex->co);
-				
-				float stiffness = params->stretch_stiffness;
-				float damping = stiffness * params->stretch_damping;
-				BPH_mass_spring_force_spring_linear(data, vi, vj, restlen, stiffness, damping, true, 0.0f, NULL, NULL, NULL);
-			}
-		}
+		strands_calc_curve_forces(strands, params, data, &it_strand);
 	}
 }