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/* SPDX-License-Identifier: GPL-2.0-or-later */
#include "BLI_length_parameterize.hh"
namespace blender::length_parameterize {
void create_uniform_samples(const Span<float> lengths,
const bool cyclic,
MutableSpan<int> indices,
MutableSpan<float> factors)
{
const int count = 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) {
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;
}
/* 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 : factors.index_range().slice(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 inacuracy. */
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);
}
}
} // namespace blender::length_parameterize
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