[Bf-blender-cvs] [399b6ec76c8] master: Mesh: optimize normal calculation
Campbell Barton
noreply at git.blender.org
Fri Aug 13 02:22:46 CEST 2021
Commit: 399b6ec76c80a8f343747a0459bb3d3df514555f
Author: Campbell Barton
Date: Fri Aug 13 09:27:29 2021 +1000
Branches: master
https://developer.blender.org/rB399b6ec76c80a8f343747a0459bb3d3df514555f
Mesh: optimize normal calculation
Optimize mesh normal calculation.
- Remove the intermediate `lnors_weighted` array, accumulate directly
into the normal array using a spin-lock for thread safety.
- Remove single threaded iteration over loops
(normal calculation is now fully multi-threaded).
- Remove stack array (alloca) for pre-calculating edge-directions.
Summary of Performance Characteristics:
- The largest gains are for single high poly meshes, with isolated
normal-calculation benchmarks of meshes over ~1.5 million showing
2x+ speedup, ~25 million polygons are ~2.85x faster.
- Single lower poly meshes (250k polys) can be ~2x slower.
Since these meshes aren't normally a bottleneck,
and this problem isn't noticeable on large scenes,
we considered the performance trade-off reasonable.
- The performance difference reduces with larger scenes,
tests with production files from "Sprite Fight" showing
the same or slightly better overall performance.
NOTE: tested on a AMD Ryzen TR 3970X 32-Core.
For more details & benchmarking scripts, see the patch description.
Reviewed By: mont29
Ref D11993
===================================================================
M source/blender/blenkernel/intern/mesh_normals.cc
===================================================================
diff --git a/source/blender/blenkernel/intern/mesh_normals.cc b/source/blender/blenkernel/intern/mesh_normals.cc
index 6bd08b3dbe0..b86332097fa 100644
--- a/source/blender/blenkernel/intern/mesh_normals.cc
+++ b/source/blender/blenkernel/intern/mesh_normals.cc
@@ -50,6 +50,8 @@
#include "BKE_global.h"
#include "BKE_mesh.h"
+#include "atomic_ops.h"
+
// #define DEBUG_TIME
#ifdef DEBUG_TIME
@@ -59,6 +61,46 @@
static CLG_LogRef LOG = {"bke.mesh_normals"};
+/* -------------------------------------------------------------------- */
+/** \name Private Utility Functions
+ * \{ */
+
+/**
+ * A thread-safe version of #add_v3_v3 that uses a spin-lock.
+ *
+ * \note Avoid using this when the chance of contention is high.
+ */
+static void add_v3_v3_atomic(float r[3], const float a[3])
+{
+#define FLT_EQ_NONAN(_fa, _fb) (*((const uint32_t *)&_fa) == *((const uint32_t *)&_fb))
+
+ float virtual_lock = r[0];
+ while (true) {
+ /* This loops until following conditions are met:
+ * - `r[0]` has same value as virtual_lock (i.e. it did not change since last try).
+ * - `r[0]` was not `FLT_MAX`, i.e. it was not locked by another thread. */
+ const float test_lock = atomic_cas_float(&r[0], virtual_lock, FLT_MAX);
+ if (_ATOMIC_LIKELY(FLT_EQ_NONAN(test_lock, virtual_lock) && (test_lock != FLT_MAX))) {
+ break;
+ }
+ virtual_lock = test_lock;
+ }
+ virtual_lock += a[0];
+ r[1] += a[1];
+ r[2] += a[2];
+
+ /* Second atomic operation to 'release'
+ * our lock on that vector and set its first scalar value. */
+ /* Note that we do not need to loop here, since we 'locked' `r[0]`,
+ * nobody should have changed it in the mean time. */
+ virtual_lock = atomic_cas_float(&r[0], FLT_MAX, virtual_lock);
+ BLI_assert(virtual_lock == FLT_MAX);
+
+#undef FLT_EQ_NONAN
+}
+
+/** \} */
+
/* -------------------------------------------------------------------- */
/** \name Mesh Normal Calculation
* \{ */
@@ -210,7 +252,6 @@ struct MeshCalcNormalsData {
const MLoop *mloop;
MVert *mverts;
float (*pnors)[3];
- float (*lnors_weighted)[3];
float (*vnors)[3];
};
@@ -224,65 +265,65 @@ static void mesh_calc_normals_poly_cb(void *__restrict userdata,
BKE_mesh_calc_poly_normal(mp, data->mloop + mp->loopstart, data->mverts, data->pnors[pidx]);
}
-static void mesh_calc_normals_poly_prepare_cb(void *__restrict userdata,
- const int pidx,
- const TaskParallelTLS *__restrict UNUSED(tls))
+static void mesh_calc_normals_poly_and_accum_cb(void *__restrict userdata,
+ const int pidx,
+ const TaskParallelTLS *__restrict UNUSED(tls))
{
- MeshCalcNormalsData *data = (MeshCalcNormalsData *)userdata;
+ const MeshCalcNormalsData *data = (MeshCalcNormalsData *)userdata;
const MPoly *mp = &data->mpolys[pidx];
const MLoop *ml = &data->mloop[mp->loopstart];
const MVert *mverts = data->mverts;
+ float(*vnors)[3] = data->vnors;
float pnor_temp[3];
float *pnor = data->pnors ? data->pnors[pidx] : pnor_temp;
- float(*lnors_weighted)[3] = data->lnors_weighted;
- const int nverts = mp->totloop;
- float(*edgevecbuf)[3] = (float(*)[3])BLI_array_alloca(edgevecbuf, (size_t)nverts);
+ const int i_end = mp->totloop - 1;
/* Polygon Normal and edge-vector */
/* inline version of #BKE_mesh_calc_poly_normal, also does edge-vectors */
{
- int i_prev = nverts - 1;
- const float *v_prev = mverts[ml[i_prev].v].co;
- const float *v_curr;
-
zero_v3(pnor);
/* Newell's Method */
- for (int i = 0; i < nverts; i++) {
- v_curr = mverts[ml[i].v].co;
- add_newell_cross_v3_v3v3(pnor, v_prev, v_curr);
-
- /* Unrelated to normalize, calculate edge-vector */
- sub_v3_v3v3(edgevecbuf[i_prev], v_prev, v_curr);
- normalize_v3(edgevecbuf[i_prev]);
- i_prev = i;
-
- v_prev = v_curr;
+ const float *v_curr = mverts[ml[i_end].v].co;
+ for (int i_next = 0; i_next <= i_end; i_next++) {
+ const float *v_next = mverts[ml[i_next].v].co;
+ add_newell_cross_v3_v3v3(pnor, v_curr, v_next);
+ v_curr = v_next;
}
if (UNLIKELY(normalize_v3(pnor) == 0.0f)) {
pnor[2] = 1.0f; /* other axes set to 0.0 */
}
}
- /* accumulate angle weighted face normal */
- /* inline version of #accumulate_vertex_normals_poly_v3,
- * split between this threaded callback and #mesh_calc_normals_poly_accum_cb. */
+ /* Accumulate angle weighted face normal into the vertex normal. */
+ /* inline version of #accumulate_vertex_normals_poly_v3. */
{
- const float *prev_edge = edgevecbuf[nverts - 1];
-
- for (int i = 0; i < nverts; i++) {
- const int lidx = mp->loopstart + i;
- const float *cur_edge = edgevecbuf[i];
-
- /* calculate angle between the two poly edges incident on
- * this vertex */
- const float fac = saacos(-dot_v3v3(cur_edge, prev_edge));
+ float edvec_prev[3], edvec_next[3], edvec_end[3];
+ const float *v_curr = mverts[ml[i_end].v].co;
+ sub_v3_v3v3(edvec_prev, mverts[ml[i_end - 1].v].co, v_curr);
+ normalize_v3(edvec_prev);
+ copy_v3_v3(edvec_end, edvec_prev);
+
+ for (int i_next = 0, i_curr = i_end; i_next <= i_end; i_curr = i_next++) {
+ const float *v_next = mverts[ml[i_next].v].co;
+
+ /* Skip an extra normalization by reusing the first calculated edge. */
+ if (i_next != i_end) {
+ sub_v3_v3v3(edvec_next, v_curr, v_next);
+ normalize_v3(edvec_next);
+ }
+ else {
+ copy_v3_v3(edvec_next, edvec_end);
+ }
- /* Store for later accumulation */
- mul_v3_v3fl(lnors_weighted[lidx], pnor, fac);
+ /* Calculate angle between the two poly edges incident on this vertex. */
+ const float fac = saacos(-dot_v3v3(edvec_prev, edvec_next));
+ const float vnor_add[3] = {pnor[0] * fac, pnor[1] * fac, pnor[2] * fac};
- prev_edge = cur_edge;
+ add_v3_v3_atomic(vnors[ml[i_curr].v], vnor_add);
+ v_curr = v_next;
+ copy_v3_v3(edvec_prev, edvec_next);
}
}
}
@@ -309,7 +350,7 @@ void BKE_mesh_calc_normals_poly(MVert *mverts,
int numVerts,
const MLoop *mloop,
const MPoly *mpolys,
- int numLoops,
+ int UNUSED(numLoops),
int numPolys,
float (*r_polynors)[3],
const bool only_face_normals)
@@ -335,8 +376,6 @@ void BKE_mesh_calc_normals_poly(MVert *mverts,
}
float(*vnors)[3] = r_vertnors;
- float(*lnors_weighted)[3] = (float(*)[3])MEM_malloc_arrayN(
- (size_t)numLoops, sizeof(*lnors_weighted), __func__);
bool free_vnors = false;
/* first go through and calculate normals for all the polys */
@@ -353,27 +392,17 @@ void BKE_mesh_calc_normals_poly(MVert *mverts,
data.mloop = mloop;
data.mverts = mverts;
data.pnors = pnors;
- data.lnors_weighted = lnors_weighted;
data.vnors = vnors;
- /* Compute poly normals, and prepare weighted loop normals. */
- BLI_task_parallel_range(0, numPolys, &data, mesh_calc_normals_poly_prepare_cb, &settings);
-
- /* Actually accumulate weighted loop normals into vertex ones. */
- /* Unfortunately, not possible to thread that
- * (not in a reasonable, totally lock- and barrier-free fashion),
- * since several loops will point to the same vertex... */
- for (int lidx = 0; lidx < numLoops; lidx++) {
- add_v3_v3(vnors[mloop[lidx].v], data.lnors_weighted[lidx]);
- }
+ /* Compute poly normals (`pnors`), accumulating them into vertex normals (`vnors`). */
+ BLI_task_parallel_range(0, numPolys, &data, mesh_calc_normals_poly_and_accum_cb, &settings);
- /* Normalize and validate computed vertex normals. */
+ /* Normalize and validate computed vertex normals (`vnors`). */
BLI_task_parallel_range(0, numVerts, &data, mesh_calc_normals_poly_finalize_cb, &settings);
if (free_vnors) {
MEM_freeN(vnors);
}
- MEM_freeN(lnors_weighted);
}
void BKE_mesh_ensure_normals(Mesh *mesh)
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