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Added combineIndexArrays() function, which can combine any number of indexarrays (i.e. number specified at runtime). The function originated in ColladaImporter plugin and is moved here to make it useful elsewhere. It is now used as base for combineIndexedArrays(), which is further simplified without unnecessary functor-like implementation. Also improved documentation. The combineIndexedArrays() function now takes std::pair instead of std::tuple, the previous version is alias to the new one, is marked as deprecated and will be removed in some future release.pull/51/head
Vladimír Vondruš
12 years ago
5 changed files with 294 additions and 77 deletions
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/*
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This file is part of Magnum. |
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Copyright © 2010, 2011, 2012, 2013, 2014 |
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Vladimír Vondruš <mosra@centrum.cz> |
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Permission is hereby granted, free of charge, to any person obtaining a |
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copy of this software and associated documentation files (the "Software"), |
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to deal in the Software without restriction, including without limitation |
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the rights to use, copy, modify, merge, publish, distribute, sublicense, |
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and/or sell copies of the Software, and to permit persons to whom the |
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Software is furnished to do so, subject to the following conditions: |
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The above copyright notice and this permission notice shall be included |
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in all copies or substantial portions of the Software. |
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
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THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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DEALINGS IN THE SOFTWARE. |
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*/ |
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#include "CombineIndexedArrays.h" |
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#include <cstring> |
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#include <unordered_map> |
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#include <Corrade/Utility/Assert.h> |
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#include <Corrade/Utility/MurmurHash2.h> |
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#include "Magnum/Magnum.h" |
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namespace Magnum { namespace MeshTools { |
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namespace Implementation { |
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std::pair<std::vector<UnsignedInt>, std::vector<UnsignedInt>> interleaveAndCombineIndexArrays(const std::reference_wrapper<const std::vector<UnsignedInt>>* begin, const std::reference_wrapper<const std::vector<UnsignedInt>>* end) { |
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/* Array stride and size */ |
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const UnsignedInt stride = end - begin; |
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const UnsignedInt inputSize = begin->get().size(); |
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#ifndef CORRADE_NO_ASSERT |
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for(auto it = begin; it != end; ++it) |
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CORRADE_ASSERT(it->get().size() == inputSize, "MeshTools::combineIndexArrays(): the arrays don't have the same size", {}); |
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#endif |
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/* Interleave the arrays */ |
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std::vector<UnsignedInt> interleavedArrays; |
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interleavedArrays.resize(inputSize*stride); |
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for(UnsignedInt offset = 0; offset != stride; ++offset) { |
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const auto& array = (begin+offset)->get(); |
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for(UnsignedInt i = 0; i != inputSize; ++i) |
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interleavedArrays[offset + i*stride] = array[i]; |
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} |
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/* Combine them */ |
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std::vector<UnsignedInt> combinedIndices; |
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std::tie(combinedIndices, interleavedArrays) = combineIndexArrays(interleavedArrays, stride); |
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return {combinedIndices, interleavedArrays}; |
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} |
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} |
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std::vector<UnsignedInt> combineIndexArrays(const std::initializer_list<std::reference_wrapper<std::vector<UnsignedInt>>> arrays) { |
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/* Interleave and combine the arrays */ |
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std::vector<UnsignedInt> combinedIndices; |
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std::vector<UnsignedInt> interleavedCombinedArrays; |
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std::tie(combinedIndices, interleavedCombinedArrays) = Implementation::interleaveAndCombineIndexArrays( |
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/* This will bite me hard once. */ |
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reinterpret_cast<const std::reference_wrapper<const std::vector<UnsignedInt>>*>(arrays.begin()), |
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reinterpret_cast<const std::reference_wrapper<const std::vector<UnsignedInt>>*>(arrays.end())); |
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/* Update the original indices */ |
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const UnsignedInt stride = arrays.size(); |
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const UnsignedInt outputSize = interleavedCombinedArrays.size()/stride; |
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for(UnsignedInt offset = 0; offset != stride; ++offset) { |
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auto& array = (arrays.begin()+offset)->get(); |
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CORRADE_INTERNAL_ASSERT(array.size() >= outputSize); |
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array.resize(outputSize); |
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for(UnsignedInt i = 0; i != outputSize; ++i) |
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array[i] = interleavedCombinedArrays[offset + i*stride]; |
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} |
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return combinedIndices; |
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} |
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namespace { |
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class IndexHash { |
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public: |
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explicit IndexHash(const std::vector<UnsignedInt>& indices, UnsignedInt stride): indices(indices), stride(stride) {} |
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std::size_t operator()(UnsignedInt key) const { |
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return *reinterpret_cast<const std::size_t*>(Utility::MurmurHash2()(reinterpret_cast<const char*>(indices.data()+key*stride), sizeof(UnsignedInt)*stride).byteArray()); |
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} |
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private: |
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const std::vector<UnsignedInt>& indices; |
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UnsignedInt stride; |
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}; |
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class IndexEqual { |
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public: |
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explicit IndexEqual(const std::vector<UnsignedInt>& indices, UnsignedInt stride): indices(indices), stride(stride) {} |
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bool operator()(UnsignedInt a, UnsignedInt b) const { |
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return std::memcmp(indices.data()+a*stride, indices.data()+b*stride, sizeof(UnsignedInt)*stride) == 0; |
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} |
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private: |
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const std::vector<UnsignedInt>& indices; |
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UnsignedInt stride; |
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}; |
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} |
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std::pair<std::vector<UnsignedInt>, std::vector<UnsignedInt>> combineIndexArrays(const std::vector<UnsignedInt>& interleavedArrays, const UnsignedInt stride) { |
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CORRADE_ASSERT(interleavedArrays.size() % stride == 0, "MeshTools::combineIndexArrays(): array size is not divisible by stride", {}); |
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/* Hash map with index combinations, containing just indices into
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interleavedArrays vector, hashing and comparison is done using IndexHash |
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and IndexEqual functors. Reserving more buckets than necessary (i.e. as |
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if each combination was unique). */ |
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std::unordered_map<UnsignedInt, UnsignedInt, IndexHash, IndexEqual> indexCombinations( |
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interleavedArrays.size()/stride, |
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IndexHash(interleavedArrays, stride), |
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IndexEqual(interleavedArrays, stride)); |
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/* Make the index combinations unique. Original indices into original
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`interleavedArrays` array were 0, 1, 2, 3, ..., `combinedIndices` |
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contains new ones into new (shorter) `newInterleavedArrays` array. */ |
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std::vector<UnsignedInt> combinedIndices; |
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combinedIndices.reserve(interleavedArrays.size()/stride); |
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std::vector<UnsignedInt> newInterleavedArrays; |
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for(std::size_t oldIndex = 0, end = interleavedArrays.size()/stride; oldIndex != end; ++oldIndex) { |
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/* Try to insert new index combination to the map */ |
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#ifndef CORRADE_GCC46_COMPATIBILITY |
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const auto result = indexCombinations.emplace(oldIndex, indexCombinations.size()); |
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#else |
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const auto result = indexCombinations.insert({oldIndex, indexCombinations.size()}); |
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#endif |
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/* Add the (either new or already existing) index to resulting index array */ |
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combinedIndices.push_back(result.first->second); |
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/* If this is new combination, copy it to new interleaved arrays */ |
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if(result.second) newInterleavedArrays.insert(newInterleavedArrays.end(), |
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interleavedArrays.begin()+oldIndex*stride, |
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interleavedArrays.begin()+(oldIndex+1)*stride); |
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} |
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CORRADE_INTERNAL_ASSERT(combinedIndices.size() == interleavedArrays.size()/stride && |
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newInterleavedArrays.size() <= interleavedArrays.size()); |
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return {std::move(combinedIndices), std::move(newInterleavedArrays)}; |
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} |
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}} |
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