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refactors hashed std::map (#3199)

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We currently apply a strange algorithm to `LightManager::mStateSetCache`. For some reason this algorithm inserts hashed keys into `std::map` in a way that fails to handle hash collisions and exhibits worse lookup complexity than `std::unordered_map`. With this PR we just use `std::unordered_map` here.
This commit is contained in:
Bo Svensson 2021-11-04 15:54:47 +00:00 committed by GitHub
parent 3042c000c6
commit 1979ee1491
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GPG key ID: 4AEE18F83AFDEB23
2 changed files with 33 additions and 17 deletions
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42
components/sceneutil/lightmanager.cpp
View file

@ -1,6 +1,8 @@
#include "lightmanager.hpp"
#include <array>
#include <algorithm>
#include <iterator>
#include <osg/BufferObject>
#include <osg/BufferIndexBinding>
@ -1158,29 +1160,39 @@ namespace SceneUtil
return mSun;
}
size_t LightManager::HashLightIdList::operator()(const LightIdList& lightIdList) const
{
size_t hash = 0;
for (size_t i = 0; i < lightIdList.size(); ++i)
Misc::hashCombine(hash, lightIdList[i]);
return hash;
}
osg::ref_ptr<osg::StateSet> LightManager::getLightListStateSet(const LightList& lightList, size_t frameNum, const osg::RefMatrix* viewMatrix)
{
// possible optimization: return a StateSet containing all requested lights plus some extra lights (if a suitable one exists)
size_t hash = 0;
for (size_t i = 0; i < lightList.size(); ++i)
if (getLightingMethod() == LightingMethod::SingleUBO)
{
auto id = lightList[i]->mLightSource->getId();
Misc::hashCombine(hash, id);
for (size_t i = 0; i < lightList.size(); ++i)
{
auto id = lightList[i]->mLightSource->getId();
if (getLightIndexMap(frameNum).find(id) != getLightIndexMap(frameNum).end())
continue;
if (getLightingMethod() != LightingMethod::SingleUBO)
continue;
if (getLightIndexMap(frameNum).find(id) != getLightIndexMap(frameNum).end())
continue;
int index = getLightIndexMap(frameNum).size() + 1;
updateGPUPointLight(index, lightList[i]->mLightSource, frameNum, viewMatrix);
getLightIndexMap(frameNum).emplace(lightList[i]->mLightSource->getId(), index);
int index = getLightIndexMap(frameNum).size() + 1;
updateGPUPointLight(index, lightList[i]->mLightSource, frameNum, viewMatrix);
getLightIndexMap(frameNum).emplace(id, index);
}
}
auto& stateSetCache = mStateSetCache[frameNum%2];
auto found = stateSetCache.find(hash);
LightIdList lightIdList;
lightIdList.reserve(lightList.size());
std::transform(lightList.begin(), lightList.end(), std::back_inserter(lightIdList), [] (const LightSourceViewBound* l) { return l->mLightSource->getId(); });
auto found = stateSetCache.find(lightIdList);
if (found != stateSetCache.end())
{
mStateSetGenerator->update(found->second, lightList, frameNum);
@ -1188,7 +1200,7 @@ namespace SceneUtil
}
auto stateset = mStateSetGenerator->generate(lightList, frameNum);
stateSetCache.emplace(hash, stateset);
stateSetCache.emplace(lightIdList, stateset);
return stateset;
}

8
components/sceneutil/lightmanager.hpp
View file

@ -207,8 +207,12 @@ namespace SceneUtil
using LightSourceViewBoundCollection = std::vector<LightSourceViewBound>;
std::map<osg::observer_ptr<osg::Camera>, LightSourceViewBoundCollection> mLightsInViewSpace;
// < Light list hash , StateSet >
using LightStateSetMap = std::map<size_t, osg::ref_ptr<osg::StateSet>>;
using LightIdList = std::vector<int>;
struct HashLightIdList
{
size_t operator()(const LightIdList&) const;
};
using LightStateSetMap = std::unordered_map<LightIdList, osg::ref_ptr<osg::StateSet>, HashLightIdList>;
LightStateSetMap mStateSetCache[2];
std::vector<osg::ref_ptr<osg::StateAttribute>> mDummies;