87 lines
3.2 KiB
C++
87 lines
3.2 KiB
C++
/*
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* Copyright 2016 The Cartographer Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "cartographer/mapping_3d/scan_matching/precomputation_grid.h"
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#include <algorithm>
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#include "Eigen/Core"
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#include "cartographer/common/math.h"
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#include "cartographer/mapping/probability_values.h"
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#include "glog/logging.h"
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namespace cartographer {
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namespace mapping_3d {
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namespace scan_matching {
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namespace {
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// C++11 defines that integer division rounds towards zero. For index math, we
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// actually need it to round towards negative infinity. Luckily bit shifts have
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// that property.
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inline int DivideByTwoRoundingTowardsNegativeInfinity(const int value) {
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return value >> 1;
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}
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// Computes the half resolution index corresponding to the full resolution
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// 'cell_index'.
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Eigen::Array3i CellIndexAtHalfResolution(const Eigen::Array3i& cell_index) {
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return Eigen::Array3i(
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DivideByTwoRoundingTowardsNegativeInfinity(cell_index[0]),
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DivideByTwoRoundingTowardsNegativeInfinity(cell_index[1]),
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DivideByTwoRoundingTowardsNegativeInfinity(cell_index[2]));
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}
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} // namespace
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PrecomputationGrid ConvertToPrecomputationGrid(const HybridGrid& hybrid_grid) {
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PrecomputationGrid result(hybrid_grid.resolution());
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for (auto it = HybridGrid::Iterator(hybrid_grid); !it.Done(); it.Next()) {
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const int cell_value = common::RoundToInt(
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(mapping::ValueToProbability(it.GetValue()) -
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mapping::kMinProbability) *
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(255.f / (mapping::kMaxProbability - mapping::kMinProbability)));
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CHECK_GE(cell_value, 0);
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CHECK_LE(cell_value, 255);
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*result.mutable_value(it.GetCellIndex()) = cell_value;
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}
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return result;
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}
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PrecomputationGrid PrecomputeGrid(const PrecomputationGrid& grid,
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const bool half_resolution,
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const Eigen::Array3i& shift) {
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PrecomputationGrid result(grid.resolution());
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for (auto it = PrecomputationGrid::Iterator(grid); !it.Done(); it.Next()) {
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for (int i = 0; i != 8; ++i) {
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// We use this value to update 8 values in the resulting grid, at
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// position (x - {0, 'shift'}, y - {0, 'shift'}, z - {0, 'shift'}).
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// If 'shift' is 2 ** (depth - 1), where depth 0 is the original grid,
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// this results in precomputation grids analogous to the 2D case.
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const Eigen::Array3i cell_index =
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it.GetCellIndex() - shift * PrecomputationGrid::GetOctant(i);
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auto* const cell_value = result.mutable_value(
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half_resolution ? CellIndexAtHalfResolution(cell_index) : cell_index);
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*cell_value = std::max(it.GetValue(), *cell_value);
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}
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}
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return result;
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}
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} // namespace scan_matching
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} // namespace mapping_3d
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} // namespace cartographer
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