OpenVDB 13.0.0

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Statistics.h
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1// Copyright Contributors to the OpenVDB Project
2// SPDX-License-Identifier: Apache-2.0
3//
4/// @file Statistics.h
5///
6/// @brief Functions to efficiently compute histograms, extrema
7/// (min/max) and statistics (mean, variance, etc.) of grid values
8
9#ifndef OPENVDB_TOOLS_STATISTICS_HAS_BEEN_INCLUDED
10#define OPENVDB_TOOLS_STATISTICS_HAS_BEEN_INCLUDED
11
12#include <openvdb/Types.h>
13#include <openvdb/Exceptions.h>
14#include <openvdb/math/Stats.h>
15#include "ValueTransformer.h"
16
17
18 namespace openvdb {
19 OPENVDB_USE_VERSION_NAMESPACE
20 namespace OPENVDB_VERSION_NAME {
21 namespace tools {
22
23/// @brief Iterate over a scalar grid and compute a histogram of the values
24/// of the voxels that are visited, or iterate over a vector-valued grid
25/// and compute a histogram of the magnitudes of the vectors.
26/// @param iter an iterator over the values of a grid or its tree
27/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
28/// @param minVal the smallest value that can be added to the histogram
29/// @param maxVal the largest value that can be added to the histogram
30/// @param numBins the number of histogram bins
31/// @param threaded if true, iterate over the grid in parallel
32 template<typename IterT>
33 inline math::Histogram
34 histogram(const IterT& iter, double minVal, double maxVal,
35 size_t numBins = 10, bool threaded = true);
36
37/// @brief Iterate over a scalar grid and compute extrema (min/max) of the
38/// values of the voxels that are visited, or iterate over a vector-valued grid
39/// and compute extrema of the magnitudes of the vectors.
40/// @param iter an iterator over the values of a grid or its tree
41/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
42/// @param threaded if true, iterate over the grid in parallel
43 template<typename IterT>
44 inline math::Extrema
45 extrema(const IterT& iter, bool threaded = true);
46
47/// @brief Iterate over a scalar grid and compute statistics (mean, variance, etc.)
48/// of the values of the voxels that are visited, or iterate over a vector-valued grid
49/// and compute statistics of the magnitudes of the vectors.
50/// @param iter an iterator over the values of a grid or its tree
51/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
52/// @param threaded if true, iterate over the grid in parallel
53 template<typename IterT>
54 inline math::Stats
55 statistics(const IterT& iter, bool threaded = true);
56
57/// @brief Iterate over a grid and compute extrema (min/max) of
58/// the values produced by applying the given functor at each voxel that is visited.
59/// @param iter an iterator over the values of a grid or its tree
60/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
61/// @param op a functor of the form <tt>void op(const IterT&, math::Stats&)</tt>,
62/// where @c IterT is the type of @a iter, that inserts zero or more
63/// floating-point values into the provided @c math::Stats object
64/// @param threaded if true, iterate over the grid in parallel
65/// @note When @a threaded is true, each thread gets its own copy of the functor.
66///
67/// @par Example:
68/// Compute statistics of just the active and positive-valued voxels of a scalar,
69/// floating-point grid.
70/// @code
71/// struct Local {
72/// static inline
73/// void addIfPositive(const FloatGrid::ValueOnCIter& iter, math::Extrema& ex)
74/// {
75/// const float f = *iter;
76/// if (f > 0.0) {
77/// if (iter.isVoxelValue()) ex.add(f);
78/// else ex.add(f, iter.getVoxelCount());
79/// }
80/// }
81/// };
82/// FloatGrid grid = ...;
83/// math::Extrema stats =
84/// tools::extrema(grid.cbeginValueOn(), Local::addIfPositive, /*threaded=*/true);
85/// @endcode
86 template<typename IterT, typename ValueOp>
87 inline math::Extrema
88 extrema(const IterT& iter, const ValueOp& op, bool threaded);
89
90/// @brief Iterate over a grid and compute statistics (mean, variance, etc.) of
91/// the values produced by applying the given functor at each voxel that is visited.
92/// @param iter an iterator over the values of a grid or its tree
93/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
94/// @param op a functor of the form <tt>void op(const IterT&, math::Stats&)</tt>,
95/// where @c IterT is the type of @a iter, that inserts zero or more
96/// floating-point values into the provided @c math::Stats object
97/// @param threaded if true, iterate over the grid in parallel
98/// @note When @a threaded is true, each thread gets its own copy of the functor.
99///
100/// @par Example:
101/// Compute statistics of just the active and positive-valued voxels of a scalar,
102/// floating-point grid.
103/// @code
104/// struct Local {
105/// static inline
106/// void addIfPositive(const FloatGrid::ValueOnCIter& iter, math::Stats& stats)
107/// {
108/// const float f = *iter;
109/// if (f > 0.0) {
110/// if (iter.isVoxelValue()) stats.add(f);
111/// else stats.add(f, iter.getVoxelCount());
112/// }
113/// }
114/// };
115/// FloatGrid grid = ...;
116/// math::Stats stats =
117/// tools::statistics(grid.cbeginValueOn(), Local::addIfPositive, /*threaded=*/true);
118/// @endcode
119 template<typename IterT, typename ValueOp>
120 inline math::Stats
121 statistics(const IterT& iter, const ValueOp& op, bool threaded);
122
123
124/// @brief Iterate over a grid and compute statistics (mean, variance, etc.)
125/// of the values produced by applying a given operator (see math/Operators.h)
126/// at each voxel that is visited.
127/// @param iter an iterator over the values of a grid or its tree
128/// (@c Grid::ValueOnCIter, @c Tree::ValueOffIter, etc.)
129/// @param op an operator object with a method of the form
130/// <tt>double result(Accessor&, const Coord&)</tt>
131/// @param threaded if true, iterate over the grid in parallel
132/// @note World-space operators, whose @c result() methods are of the form
133/// <tt>double result(const Map&, Accessor&, const Coord&)</tt>, must be wrapped
134/// in a math::MapAdapter.
135/// @note Vector-valued operators like math::Gradient must be wrapped in an adapter
136/// such as math::OpMagnitude.
137///
138/// @par Example:
139/// Compute statistics of the magnitude of the gradient at the active voxels of
140/// a scalar, floating-point grid. (Note the use of the math::MapAdapter and
141/// math::OpMagnitude adapters.)
142/// @code
143/// FloatGrid grid = ...;
144///
145/// // Assume that we know that the grid has a uniform scale map.
146/// using MapType = math::UniformScaleMap;
147/// // Specify a world-space gradient operator that uses first-order differencing.
148/// using GradientOp = math::Gradient<MapType, math::FD_1ST>;
149/// // Wrap the operator with an adapter that computes the magnitude of the gradient.
150/// using MagnitudeOp = math::OpMagnitude<GradientOp, MapType>;
151/// // Wrap the operator with an adapter that associates a map with it.
152/// using CompoundOp = math::MapAdapter<MapType, GradientOp, double>;
153///
154/// if (MapType::Ptr map = grid.constTransform().constMap<MapType>()) {
155/// math::Stats stats = tools::opStatistics(grid.cbeginValueOn(), CompoundOp(*map));
156/// }
157/// @endcode
158///
159/// @par Example:
160/// Compute statistics of the divergence at the active voxels of a vector-valued grid.
161/// @code
162/// Vec3SGrid grid = ...;
163///
164/// // Assume that we know that the grid has a uniform scale map.
165/// using MapType = math::UniformScaleMap;
166/// // Specify a world-space divergence operator that uses first-order differencing.
167/// using DivergenceOp = math::Divergence<MapType, math::FD_1ST>;
168/// // Wrap the operator with an adapter that associates a map with it.
169/// using CompoundOp = math::MapAdapter<MapType, DivergenceOp, double>;
170///
171/// if (MapType::Ptr map = grid.constTransform().constMap<MapType>()) {
172/// math::Stats stats = tools::opStatistics(grid.cbeginValueOn(), CompoundOp(*map));
173/// }
174/// @endcode
175///
176/// @par Example:
177/// As above, but computing the divergence in index space.
178/// @code
179/// Vec3SGrid grid = ...;
180///
181/// // Specify an index-space divergence operator that uses first-order differencing.
182/// using DivergenceOp = math::ISDivergence<math::FD_1ST>;
183///
184/// math::Stats stats = tools::opStatistics(grid.cbeginValueOn(), DivergenceOp());
185/// @endcode
186 template<typename OperatorT, typename IterT>
187 inline math::Stats
188 opStatistics(const IterT& iter, const OperatorT& op = OperatorT(), bool threaded = true);
189
190/// @brief Same as opStatistics except it returns a math::Extrema vs a math::Stats
191 template<typename OperatorT, typename IterT>
192 inline math::Extrema
193 opExtrema(const IterT& iter, const OperatorT& op = OperatorT(), bool threaded = true);
194
195////////////////////////////////////////
196
197/// @cond OPENVDB_DOCS_INTERNAL
198
199 namespace stats_internal {
200
201/// @todo This traits class is needed because tree::TreeValueIteratorBase uses
202/// the name ValueT for the type of the value to which the iterator points,
203/// whereas node-level iterators use the name ValueType.
204 template<typename IterT, typename AuxT = void>
205 struct IterTraits {
206 using ValueType = typename IterT::ValueType;
207};
208
209 template<typename TreeT, typename ValueIterT>
210 struct IterTraits<tree::TreeValueIteratorBase<TreeT, ValueIterT> > {
211 using ValueType = typename tree::TreeValueIteratorBase<TreeT, ValueIterT>::ValueT;
212};
213
214
215// Helper class to compute a scalar value from either a scalar or a vector value
216// (the latter by computing the vector's magnitude)
217 template<typename T, bool IsVector> struct GetValImpl;
218
219 template<typename T>
220 struct GetValImpl<T, /*IsVector=*/false> {
221 static inline double get(const T& val) { return double(val); }
222};
223
224 template<typename T>
225 struct GetValImpl<T, /*IsVector=*/true> {
226 static inline double get(const T& val) { return val.length(); }
227};
228
229
230// Helper class to compute a scalar value from a tree or node iterator
231// that points to a value in either a scalar or a vector grid, and to
232// add that value to a math::Stats object.
233 template<typename IterT, typename StatsT>
234 struct GetVal
235{
236 using ValueT = typename IterTraits<IterT>::ValueType;
237 using ImplT = GetValImpl<ValueT, VecTraits<ValueT>::IsVec>;
238
239 inline void operator()(const IterT& iter, StatsT& stats) const {
240 if (iter.isVoxelValue()) stats.add(ImplT::get(*iter));
241 else stats.add(ImplT::get(*iter), iter.getVoxelCount());
242 }
243};
244
245// Helper class to accumulate scalar voxel values or vector voxel magnitudes
246// into a math::Stats object
247 template<typename IterT, typename ValueOp, typename StatsT>
248 struct StatsOp
249{
250 StatsOp(const ValueOp& op): getValue(op) {}
251
252 // Accumulate voxel and tile values into this functor's Stats object.
253 inline void operator()(const IterT& iter) { getValue(iter, stats); }
254
255 // Accumulate another functor's Stats object into this functor's.
256 inline void join(StatsOp& other) { stats.add(other.stats); }
257
258 StatsT stats;
259 ValueOp getValue;
260};
261
262
263// Helper class to accumulate scalar voxel values or vector voxel magnitudes
264// into a math::Histogram object
265 template<typename IterT, typename ValueOp>
266 struct HistOp
267{
268 HistOp(const ValueOp& op, double vmin, double vmax, size_t bins):
269 hist(vmin, vmax, bins), getValue(op)
270 {}
271
272 // Accumulate voxel and tile values into this functor's Histogram object.
273 inline void operator()(const IterT& iter) { getValue(iter, hist); }
274
275 // Accumulate another functor's Histogram object into this functor's.
276 inline void join(HistOp& other) { hist.add(other.hist); }
277
278 math::Histogram hist;
279 ValueOp getValue;
280};
281
282
283// Helper class to apply an operator such as math::Gradient or math::Laplacian
284// to voxels and accumulate the scalar results or the magnitudes of vector results
285// into a math::Stats object
286 template<typename IterT, typename OpT, typename StatsT>
287 struct MathOp
288{
289 using TreeT = typename IterT::TreeT;
290 using ValueT = typename TreeT::ValueType;
291 using ConstAccessor = typename tree::ValueAccessor<const TreeT>;
292
293 // Each thread gets its own accessor and its own copy of the operator.
294 ConstAccessor mAcc;
295 OpT mOp;
296 StatsT mStats;
297
298 template<typename TreeT>
299 static inline TreeT* THROW_IF_NULL(TreeT* ptr) {
300 if (ptr == nullptr) OPENVDB_THROW(ValueError, "iterator references a null tree");
301 return ptr;
302 }
303
304 MathOp(const IterT& iter, const OpT& op):
305 mAcc(*THROW_IF_NULL(iter.getTree())), mOp(op)
306 {}
307
308 // Accumulate voxel and tile values into this functor's Stats object.
309 void operator()(const IterT& it)
310 {
311 if (it.isVoxelValue()) {
312 // Add the magnitude of the gradient at a single voxel.
313 mStats.add(mOp.result(mAcc, it.getCoord()));
314 } else {
315 // Iterate over the voxels enclosed by a tile and add the results
316 // of applying the operator at each voxel.
317 /// @todo This could be specialized to be done more efficiently for some operators.
318 /// For example, all voxels in the interior of a tile (i.e., not on the borders)
319 /// have gradient zero, so there's no need to apply the operator to every voxel.
320 CoordBBox bbox = it.getBoundingBox();
321 Coord xyz;
322 int &x = xyz.x(), &y = xyz.y(), &z = xyz.z();
323 for (x = bbox.min().x(); x <= bbox.max().x(); ++x) {
324 for (y = bbox.min().y(); y <= bbox.max().y(); ++y) {
325 for (z = bbox.min().z(); z <= bbox.max().z(); ++z) {
326 mStats.add(mOp.result(mAcc, it.getCoord()));
327 }
328 }
329 }
330 }
331 }
332
333 // Accumulate another functor's Stats object into this functor's.
334 inline void join(MathOp& other) { mStats.add(other.mStats); }
335}; // struct MathOp
336
337} // namespace stats_internal
338
339/// @endcond
340
341 template<typename IterT>
342 inline math::Histogram
343 histogram(const IterT& iter, double vmin, double vmax, size_t numBins, bool threaded)
344{
345 using ValueOp = stats_internal::GetVal<IterT, math::Histogram>;
346 ValueOp valOp;
347 stats_internal::HistOp<IterT, ValueOp> op(valOp, vmin, vmax, numBins);
348 tools::accumulate(iter, op, threaded);
349 return op.hist;
350}
351
352 template<typename IterT>
353 inline math::Extrema
354 extrema(const IterT& iter, bool threaded)
355{
356 stats_internal::GetVal<IterT, math::Extrema> valOp;
357 return extrema(iter, valOp, threaded);
358}
359
360 template<typename IterT>
361 inline math::Stats
362 statistics(const IterT& iter, bool threaded)
363{
364 stats_internal::GetVal<IterT, math::Stats> valOp;
365 return statistics(iter, valOp, threaded);
366}
367
368 template<typename IterT, typename ValueOp>
369 inline math::Extrema
370 extrema(const IterT& iter, const ValueOp& valOp, bool threaded)
371{
372 stats_internal::StatsOp<IterT, const ValueOp, math::Extrema> op(valOp);
373 tools::accumulate(iter, op, threaded);
374 return op.stats;
375}
376
377 template<typename IterT, typename ValueOp>
378 inline math::Stats
379 statistics(const IterT& iter, const ValueOp& valOp, bool threaded)
380{
381 stats_internal::StatsOp<IterT, const ValueOp, math::Stats> op(valOp);
382 tools::accumulate(iter, op, threaded);
383 return op.stats;
384}
385
386
387 template<typename OperatorT, typename IterT>
388 inline math::Extrema
389 opExtrema(const IterT& iter, const OperatorT& op, bool threaded)
390{
391 stats_internal::MathOp<IterT, OperatorT, math::Extrema> func(iter, op);
392 tools::accumulate(iter, func, threaded);
393 return func.mStats;
394}
395
396 template<typename OperatorT, typename IterT>
397 inline math::Stats
398 opStatistics(const IterT& iter, const OperatorT& op, bool threaded)
399{
400 stats_internal::MathOp<IterT, OperatorT, math::Stats> func(iter, op);
401 tools::accumulate(iter, func, threaded);
402 return func.mStats;
403}
404
405} // namespace tools
406} // namespace OPENVDB_VERSION_NAME
407} // namespace openvdb
408
409#endif // OPENVDB_TOOLS_STATISTICS_HAS_BEEN_INCLUDED
Stats.h
Classes to compute statistics and histograms.
ValueTransformer.h
openvdb::v13_0::math::Extrema
This class computes the minimum and maximum values of a population of floating-point values.
Definition Stats.h:90
openvdb::v13_0::math::Stats
This class computes statistics (minimum value, maximum value, mean, variance and standard deviation) ...
Definition Stats.h:180
openvdb::v13_0::tools::statistics
math::Stats statistics(const IterT &iter, bool threaded=true)
Iterate over a scalar grid and compute statistics (mean, variance, etc.) of the values of the voxels ...
Definition Statistics.h:362
openvdb::v13_0::tools::opStatistics
math::Stats opStatistics(const IterT &iter, const OperatorT &op=OperatorT(), bool threaded=true)
Iterate over a grid and compute statistics (mean, variance, etc.) of the values produced by applying ...
Definition Statistics.h:398
openvdb::v13_0::tools::op
OutGridT XformOp & op
Definition ValueTransformer.h:140
openvdb::v13_0::tools::histogram
math::Histogram histogram(const IterT &iter, double minVal, double maxVal, size_t numBins=10, bool threaded=true)
Iterate over a scalar grid and compute a histogram of the values of the voxels that are visited,...
Definition Statistics.h:343
openvdb::v13_0::tools::accumulate
void accumulate(const IterT &iter, XformOp &op, bool threaded=true)
Definition ValueTransformer.h:683
openvdb::v13_0::tools::opExtrema
math::Extrema opExtrema(const IterT &iter, const OperatorT &op=OperatorT(), bool threaded=true)
Same as opStatistics except it returns a math::Extrema vs a math::Stats.
Definition Statistics.h:389
openvdb::v13_0::tools::extrema
math::Extrema extrema(const IterT &iter, bool threaded=true)
Iterate over a scalar grid and compute extrema (min/max) of the values of the voxels that are visited...
Definition Statistics.h:354
openvdb::v13_0::tools::threaded
OutGridT XformOp bool threaded
Definition ValueTransformer.h:140
openvdb
Definition Exceptions.h:13
Exceptions.h
OPENVDB_THROW
#define OPENVDB_THROW(exception, message)
Definition Exceptions.h:74
Types.h
OPENVDB_VERSION_NAME
#define OPENVDB_VERSION_NAME
The version namespace name for this library version.
Definition version.h.in:121
OPENVDB_USE_VERSION_NAMESPACE
#define OPENVDB_USE_VERSION_NAMESPACE
Definition version.h.in:218