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BLI: refactor length parameterization 

This refactor had two main goals:
* Simplify the sampling code by using an algorithm with fewer special cases.
* Generalize the sampling to support non-sorted samples.

The `SampleSegmentHint` optimization was inspired by `ValueAccessor` from
OpenVDB and improves performance 2x in my test cases.

Differential Revision: https://developer.blender.org/D15348
This commit is contained in:
Jacques Lucke 2022-07-02 21:51:45 +02:00
parent 69ee9ca90e
commit ab444a80a2
Notes: blender-bot 2023-02-14 02:27:51 +01:00 
Referenced by issue #99370, Length parameterization failure case
Referenced by issue #99287, Regression: Resample Curve after Fillet Curve node cause crash randomly
5 changed files with 150 additions and 173 deletions
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139
source/blender/blenlib/BLI_length_parameterize.hh
View File

@ -19,7 +19,7 @@ namespace blender::length_parameterize {
*
* \note This is the same as #bke::curves::curve_segment_num.
*/
inline int lengths_num(const int points_num, const bool cyclic)
inline int segments_num(const int points_num, const bool cyclic)
{
return cyclic ? points_num : points_num - 1;
}
@ -30,7 +30,7 @@ inline int lengths_num(const int points_num, const bool cyclic)
template<typename T>
void accumulate_lengths(const Span<T> values, const bool cyclic, MutableSpan<float> lengths)
{
BLI_assert(lengths.size() == lengths_num(values.size(), cyclic));
BLI_assert(lengths.size() == segments_num(values.size(), cyclic));
float length = 0.0f;
for (const int i : IndexRange(values.size() - 1)) {
length += math::distance(values[i], values[i + 1]);
@ -42,57 +42,122 @@ void accumulate_lengths(const Span<T> values, const bool cyclic, MutableSpan<flo
}
template<typename T>
void linear_interpolation(const Span<T> src,
const Span<int> indices,
const Span<float> factors,
MutableSpan<T> dst)
inline void linear_interpolation(const Span<T> src,
const Span<int> indices,
const Span<float> factors,
MutableSpan<T> dst)
{
BLI_assert(indices.size() == factors.size());
BLI_assert(indices.size() == dst.size());
const int last_src_index = src.index_range().last();
const int last_src_index = src.size() - 1;
int cyclic_sample_count = 0;
for (int i = indices.index_range().last(); i > 0; i--) {
if (indices[i] != last_src_index) {
break;
for (const int i : dst.index_range()) {
const int prev_index = indices[i];
const float factor = factors[i];
const bool is_cyclic_case = prev_index == last_src_index;
if (is_cyclic_case) {
dst[i] = math::interpolate(src.last(), src.first(), factor);
}
else {
dst[i] = math::interpolate(src[prev_index], src[prev_index + 1], factor);
}
dst[i] = math::interpolate(src.last(), src.first(), factors[i]);
cyclic_sample_count++;
}
for (const int i : dst.index_range().drop_back(cyclic_sample_count)) {
dst[i] = math::interpolate(src[indices[i]], src[indices[i] + 1], factors[i]);
}
}
/**
* Find the given number of points, evenly spaced along the provided length. For non-cyclic
* sequences, the first point will always be included, and last point will always be included if
* the #count is greater than zero. For cyclic sequences, the first point will always be included.
*
* \warning The #count argument must be greater than zero.
* Passing this to consecutive calls of #sample_at_length can increase performance.
*/
void create_uniform_samples(Span<float> lengths,
bool cyclic,
MutableSpan<int> indices,
MutableSpan<float> factors);
struct SampleSegmentHint {
int segment_index = -1;
float segment_start;
float segment_length_inv;
};
/**
* \param accumulated_segment_lengths: Lengths of individual segments added up.
* \param sample_length: The position to sample at.
* \param r_segment_index: Returns the index of the segment that #sample_length is in.
* \param r_factor: Returns the position within the segment.
*
* \note #sample_length must not be outside of any segment.
*/
inline void sample_at_length(const Span<float> accumulated_segment_lengths,
float sample_length,
int &r_segment_index,
float &r_factor,
SampleSegmentHint *hint = nullptr)
{
/* Use a shorter variable name. */
const Span<float> lengths = accumulated_segment_lengths;
BLI_assert(lengths.size() > 0);
BLI_assert(sample_length >= 0.0f);
BLI_assert(sample_length <= lengths.last());
if (hint != nullptr && hint->segment_index >= 0) {
const float length_in_segment = sample_length - hint->segment_start;
const float factor = length_in_segment * hint->segment_length_inv;
if (factor >= 0.0f && factor < 1.0f) {
r_segment_index = hint->segment_index;
r_factor = factor;
return;
}
}
const float total_length = lengths.last();
if (sample_length >= total_length) {
/* Return the last position on the last segment. */
r_segment_index = lengths.size() - 1;
r_factor = 1.0f;
return;
}
const int prev_point_index = std::upper_bound(lengths.begin(), lengths.end(), sample_length) -
lengths.begin();
const float segment_start = prev_point_index == 0 ? 0.0f : lengths[prev_point_index - 1];
const float segment_end = lengths[prev_point_index];
const float segment_length = segment_end - segment_start;
const float segment_length_inv = safe_divide(1.0f, segment_length);
const float length_in_segment = sample_length - segment_start;
const float factor = length_in_segment * segment_length_inv;
r_segment_index = prev_point_index;
r_factor = factor;
if (hint != nullptr) {
hint->segment_index = r_segment_index;
hint->segment_start = segment_start;
hint->segment_length_inv = segment_length_inv;
}
}
/**
* Find evenly spaced samples along the lengths.
*
* \param accumulated_segment_lengths: The accumulated lengths of the original elements being
* sampled. Could be calculated by #accumulate_lengths.
* \param include_last_point: Generally false for cyclic sequences and true otherwise.
* \param r_segment_indices: The index of the previous point at each sample.
* \param r_factors: The portion of the length in each segment at each sample.
*/
void sample_uniform(Span<float> accumulated_segment_lengths,
bool include_last_point,
MutableSpan<int> r_segment_indices,
MutableSpan<float> r_factors);
/**
* For each provided sample length, find the segment index and interpolation factor.
*
* \param lengths: The accumulated lengths of the original elements being sampled.
* Could be calculated by #accumulate_lengths.
* \param accumulated_segment_lengths: The accumulated lengths of the original elements being
* sampled. Could be calculated by #accumulate_lengths.
* \param sample_lengths: Sampled locations in the #lengths array. Must be sorted and is expected
* to be within the range of the #lengths values.
* \param cyclic: Whether the points described by the #lengths input is cyclic. This is likely
* redundant information theoretically.
* \param indices: The index of the previous point at each sample.
* \param factors: The portion of the length in each segment at each sample.
* \param r_segment_indices: The index of the previous point at each sample.
* \param r_factors: The portion of the length in each segment at each sample.
*/
void create_samples_from_sorted_lengths(Span<float> lengths,
Span<float> sample_lengths,
bool cyclic,
MutableSpan<int> indices,
MutableSpan<float> factors);
void sample_at_lengths(Span<float> accumulated_segment_lengths,
Span<float> sample_lengths,
MutableSpan<int> r_segment_indices,
MutableSpan<float> r_factors);
} // namespace blender::length_parameterize

150
source/blender/blenlib/intern/length_parameterize.cc
View File

@ -1,144 +1,58 @@
/* SPDX-License-Identifier: GPL-2.0-or-later */
#include "BLI_length_parameterize.hh"
#include "BLI_task.hh"
namespace blender::length_parameterize {
void create_uniform_samples(const Span<float> lengths,
const bool cyclic,
MutableSpan<int> indices,
MutableSpan<float> factors)
void sample_uniform(const Span<float> lengths,
const bool include_last_point,
MutableSpan<int> r_segment_indices,
MutableSpan<float> r_factors)
{
const int count = indices.size();
const int count = r_segment_indices.size();
BLI_assert(count > 0);
BLI_assert(lengths.size() >= 1);
BLI_assert(std::is_sorted(lengths.begin(), lengths.end()));
const int segments_num = lengths.size();
const int points_num = cyclic ? segments_num : segments_num + 1;
indices.first() = 0;
factors.first() = 0.0f;
if (count == 1) {
r_segment_indices[0] = 0;
r_factors[0] = 0.0f;
return;
}
const float total_length = lengths.last();
if (total_length == 0.0f) {
indices.fill(0);
factors.fill(0.0f);
return;
}
const float step_length = total_length / (count - (cyclic ? 0 : 1));
const float step_length_inv = 1.0f / step_length;
int i_dst = 1;
/* Store the length at the previous point in a variable so it can start out at zero
* (the lengths array doesn't contain 0 for the first point). */
float prev_length = 0.0f;
for (const int i_src : IndexRange(points_num - 1)) {
const float next_length = lengths[i_src];
const float segment_length = next_length - prev_length;
if (segment_length == 0.0f) {
continue;
const float step_length = total_length / (count - include_last_point);
threading::parallel_for(IndexRange(count), 512, [&](const IndexRange range) {
SampleSegmentHint hint;
for (const int i : range) {
/* Use minimum to avoid issues with floating point accuracy. */
const float sample_length = std::min(total_length, i * step_length);
sample_at_length(lengths, sample_length, r_segment_indices[i], r_factors[i], &hint);
}
/* Add every sample that fits in this segment. */
const float segment_length_inv = 1.0f / segment_length;
const int segment_samples_num = std::ceil(next_length * step_length_inv - i_dst);
indices.slice(i_dst, segment_samples_num).fill(i_src);
for (const int i : IndexRange(i_dst, segment_samples_num)) {
const float length_in_segment = step_length * i - prev_length;
factors[i] = length_in_segment * segment_length_inv;
}
i_dst += segment_samples_num;
prev_length = next_length;
}
/* Add the samples on the last cyclic segment if necessary, and also the samples
* that weren't created in the previous loop due to floating point inaccuracy. */
if (cyclic && lengths.size() > 1) {
indices.drop_front(i_dst).fill(points_num - 1);
const float segment_length = lengths.last() - lengths.last(1);
if (segment_length == 0.0f) {
return;
}
const float segment_length_inv = 1.0f / segment_length;
for (const int i : indices.index_range().drop_front(i_dst)) {
const float length_in_segment = step_length * i - prev_length;
factors[i] = length_in_segment * segment_length_inv;
}
}
else {
indices.drop_front(i_dst).fill(points_num - 2);
factors.drop_front(i_dst).fill(1.0f);
}
});
}
void create_samples_from_sorted_lengths(const Span<float> lengths,
const Span<float> sample_lengths,
const bool cyclic,
MutableSpan<int> indices,
MutableSpan<float> factors)
void sample_at_lengths(const Span<float> accumulated_segment_lengths,
const Span<float> sample_lengths,
MutableSpan<int> r_segment_indices,
MutableSpan<float> r_factors)
{
BLI_assert(std::is_sorted(lengths.begin(), lengths.end()));
BLI_assert(
std::is_sorted(accumulated_segment_lengths.begin(), accumulated_segment_lengths.end()));
BLI_assert(std::is_sorted(sample_lengths.begin(), sample_lengths.end()));
BLI_assert(indices.size() == sample_lengths.size());
BLI_assert(indices.size() == factors.size());
const int segments_num = lengths.size();
const int points_num = cyclic ? segments_num : segments_num + 1;
const float total_length = lengths.last();
if (total_length == 0.0f) {
indices.fill(0);
factors.fill(0.0f);
return;
}
const int count = sample_lengths.size();
BLI_assert(count == r_segment_indices.size());
BLI_assert(count == r_factors.size());
int i_dst = 0;
/* Store the length at the previous point in a variable so it can start out at zero
* (the lengths array doesn't contain 0 for the first point). */
float prev_length = 0.0f;
for (const int i_src : IndexRange(points_num - 1)) {
const float next_length = lengths[i_src];
const float segment_length = next_length - prev_length;
if (segment_length == 0.0f) {
continue;
threading::parallel_for(IndexRange(count), 512, [&](const IndexRange range) {
SampleSegmentHint hint;
for (const int i : range) {
const float sample_length = sample_lengths[i];
sample_at_length(
accumulated_segment_lengths, sample_length, r_segment_indices[i], r_factors[i], &hint);
}
/* Add every sample that fits in this segment. It's also necessary to check if the last sample
* has been reached, since there is no upper bound on the number of samples in each segment. */
const float segment_length_inv = 1.0f / segment_length;
while (i_dst < sample_lengths.size() && sample_lengths[i_dst] < next_length) {
const float length_in_segment = sample_lengths[i_dst] - prev_length;
const float factor = length_in_segment * segment_length_inv;
indices[i_dst] = i_src;
factors[i_dst] = factor;
i_dst++;
}
prev_length = next_length;
}
/* Add the samples on the last cyclic segment if necessary, and also the samples
* that weren't created in the previous loop due to floating point inaccuracy. */
if (cyclic && lengths.size() > 1) {
const float segment_length = lengths.last() - lengths.last(1);
while (sample_lengths[i_dst] < total_length) {
const float length_in_segment = sample_lengths[i_dst] - prev_length;
const float factor = length_in_segment / segment_length;
indices[i_dst] = points_num - 1;
factors[i_dst] = factor;
i_dst++;
}
indices.drop_front(i_dst).fill(points_num - 1);
factors.drop_front(i_dst).fill(1.0f);
}
else {
indices.drop_front(i_dst).fill(points_num - 2);
factors.drop_front(i_dst).fill(1.0f);
}
});
}
} // namespace blender::length_parameterize

20
source/blender/blenlib/tests/BLI_length_parameterize_test.cc
View File

@ -10,7 +10,7 @@ namespace blender::length_parameterize::tests {
template<typename T> Array<float> calculate_lengths(const Span<T> values, const bool cyclic)
{
Array<float> lengths(lengths_num(values.size(), cyclic));
Array<float> lengths(segments_num(values.size(), cyclic));
accumulate_lengths<T>(values, cyclic, lengths);
return lengths;
}
@ -30,7 +30,7 @@ TEST(length_parameterize, FloatSimple)
Array<int> indices(4);
Array<float> factors(4);
create_uniform_samples(lengths, false, indices, factors);
sample_uniform(lengths, true, indices, factors);
Array<float> results(4);
linear_interpolation<float>(values, indices, factors, results);
Array<float> expected({
@ -52,7 +52,7 @@ TEST(length_parameterize, Float)
Array<int> indices(20);
Array<float> factors(20);
create_uniform_samples(lengths, false, indices, factors);
sample_uniform(lengths, true, indices, factors);
Array<float> results(20);
linear_interpolation<float>(values, indices, factors, results);
Array<float> expected({
@ -73,7 +73,7 @@ TEST(length_parameterize, Float2)
Array<int> indices(12);
Array<float> factors(12);
create_uniform_samples(lengths, false, indices, factors);
sample_uniform(lengths, true, indices, factors);
Array<float2> results(12);
linear_interpolation<float2>(values, indices, factors, results);
Array<float2> expected({
@ -103,7 +103,7 @@ TEST(length_parameterize, Float2Cyclic)
Array<int> indices(12);
Array<float> factors(12);
create_uniform_samples(lengths, true, indices, factors);
sample_uniform(lengths, false, indices, factors);
Array<float2> results(12);
linear_interpolation<float2>(values, indices, factors, results);
Array<float2> expected({
@ -133,7 +133,7 @@ TEST(length_parameterize, LineMany)
Array<int> indices(5007);
Array<float> factors(5007);
create_uniform_samples(lengths, false, indices, factors);
sample_uniform(lengths, true, indices, factors);
Array<float> results(5007);
linear_interpolation<float>(values, indices, factors, results);
Array<float> expected({
@ -152,7 +152,7 @@ TEST(length_parameterize, CyclicMany)
Array<int> indices(5007);
Array<float> factors(5007);
create_uniform_samples(lengths, true, indices, factors);
sample_uniform(lengths, false, indices, factors);
Array<float2> results(5007);
linear_interpolation<float2>(values, indices, factors, results);
Array<float2> expected({
@ -176,7 +176,7 @@ TEST(length_parameterize, InterpolateColor)
Array<int> indices(10);
Array<float> factors(10);
create_uniform_samples(lengths, true, indices, factors);
sample_uniform(lengths, false, indices, factors);
Array<ColorGeometry4f> results(10);
linear_interpolation<ColorGeometry4f>(colors, indices, factors, results);
Array<ColorGeometry4f> expected({
@ -207,7 +207,7 @@ TEST(length_parameterize, ArbitraryFloatSimple)
Array<float> sample_lengths{{0.5f, 1.5f, 2.0f, 4.0f}};
Array<int> indices(4);
Array<float> factors(4);
create_samples_from_sorted_lengths(lengths, sample_lengths, false, indices, factors);
sample_at_lengths(lengths, sample_lengths, indices, factors);
Array<float> results(4);
linear_interpolation<float>(values, indices, factors, results);
results.as_span().print_as_lines("results");
@ -231,7 +231,7 @@ TEST(length_parameterize, ArbitraryFloat2)
{0.5f, 1.5f, 2.0f, 2.0f, 2.1f, 2.5f, 3.5f, 3.6f, 3.8f, 3.85f, 3.90f, 4.0f}};
Array<int> indices(12);
Array<float> factors(12);
create_samples_from_sorted_lengths(lengths, sample_lengths, true, indices, factors);
sample_at_lengths(lengths, sample_lengths, indices, factors);
Array<float2> results(12);
linear_interpolation<float2>(values, indices, factors, results);
results.as_span().print_as_lines("results");

5
source/blender/editors/sculpt_paint/curves_sculpt_brush.cc
View File

@ -345,7 +345,7 @@ void move_last_point_and_resample(MutableSpan<float3> positions, const float3 &n
{
/* Find the accumulated length of each point in the original curve,
* treating it as a poly curve for performance reasons and simplicity. */
Array<float> orig_lengths(length_parameterize::lengths_num(positions.size(), false));
Array<float> orig_lengths(length_parameterize::segments_num(positions.size(), false));
length_parameterize::accumulate_lengths<float3>(positions, false, orig_lengths);
const float orig_total_length = orig_lengths.last();
@ -363,8 +363,7 @@ void move_last_point_and_resample(MutableSpan<float3> positions, const float3 &n
Array<int> indices(positions.size() - 1);
Array<float> factors(positions.size() - 1);
length_parameterize::create_samples_from_sorted_lengths(
orig_lengths, new_lengths, false, indices, factors);
length_parameterize::sample_at_lengths(orig_lengths, new_lengths, indices, factors);
Array<float3> new_positions(positions.size() - 1);
length_parameterize::linear_interpolation<float3>(positions, indices, factors, new_positions);

9
source/blender/geometry/intern/resample_curves.cc
View File

@ -234,11 +234,10 @@ static Curves *resample_to_uniform(const CurveComponent &src_component,
for (const int i_curve : sliced_selection) {
const bool cyclic = curves_cyclic[i_curve];
const IndexRange dst_points = dst_curves.points_for_curve(i_curve);
length_parameterize::create_uniform_samples(
src_curves.evaluated_lengths_for_curve(i_curve, cyclic),
curves_cyclic[i_curve],
sample_indices.as_mutable_span().slice(dst_points),
sample_factors.as_mutable_span().slice(dst_points));
length_parameterize::sample_uniform(src_curves.evaluated_lengths_for_curve(i_curve, cyclic),
!curves_cyclic[i_curve],
sample_indices.as_mutable_span().slice(dst_points),
sample_factors.as_mutable_span().slice(dst_points));
}
/* For every attribute, evaluate attributes from every curve in the range in the original