//创建新的点云，可视的选择集

ccGenericPointCloud* ccPointCloud::createNewCloudFromVisibilitySelection(bool removeSelectedPoints)

{

	if (!isVisibilityTableInstantiated())

	{

		ccLog::Error(QString("[Cloud %1] Visibility table not instantiated!").arg(getName()));

		return 0;

	}

	//we create a new cloud with the "visible" points

	ccPointCloud* result = 0;

	{

		//we create a temporary entity with the visible points only

		CCLib::ReferenceCloud* rc = getTheVisiblePoints();

		if (!rc)

		{

			//a warning message has already been issued by getTheVisiblePoints!

			//ccLog::Warning("[ccPointCloud::createNewCloudFromVisibilitySelection] An error occurred during points selection!");

			return 0;

		}

		assert(rc->size() != 0);

		//convert selection to cloud

		result = partialClone(rc);

		//don't need this one anymore

		delete rc;

		rc = 0;

	}

	if (!result)

	{

		ccLog::Warning("[ccPointCloud::createNewCloudFromVisibilitySelection] An error occurred during segmentation!");

		return 0;

	}

	result->setName(getName()+QString(".segmented"));//切割出来的点云

	//shall the visible points be erased from this cloud?

	if (removeSelectedPoints && !isLocked())

	{

		//we drop the octree before modifying this cloud's contents

		deleteOctree();

		clearLOD();

		unsigned count = size();

		//we have to take care of scan grids first

		{

			//we need a map between old and new indexes

			std::vector<int> newIndexMap(size(), -1);

			{

				unsigned newIndex = 0;

				for (unsigned i=0; i<count; ++i)

				{

					if (m_pointsVisibility->getValue(i) != POINT_VISIBLE)

						newIndexMap[i] = newIndex++;

				}

			}

			//then update the indexes

			UpdateGridIndexes(newIndexMap, m_grids);

			//and reset the invalid (empty) ones

			//(DGM: we don't erase them as they may still be useful?)

			for (size_t i=0; i<m_grids.size(); ++i)

			{

				Grid::Shared& scanGrid = m_grids[i];

				if (scanGrid->validCount == 0)

				{

					scanGrid->indexes.clear();

				}

			}

		}

		//we remove all visible points

		unsigned lastPoint = 0;

		for (unsigned i=0; i<count; ++i)

		{

			//i持续增长，而lastPoint遇到==POINT_VISIBLE则跳过，起到迁移的效果

			if (m_pointsVisibility->getValue(i) != POINT_VISIBLE)

			{

				if (i != lastPoint)

					swapPoints(lastPoint,i);

				++lastPoint;

			}

		}

		//TODO: handle associated meshes

		resize(lastPoint);

		refreshBB(); //calls notifyGeometryUpdate + releaseVBOs

	}

	return result;

}

CCLib::ReferenceCloud* ccGenericPointCloud::getTheVisiblePoints() const

{

	unsigned count = size();

	assert(count == m_pointsVisibility->currentSize());

	if (!m_pointsVisibility || m_pointsVisibility->currentSize() != count)

	{

		ccLog::Warning("[ccGenericPointCloud::getTheVisiblePoints] No visibility table instantiated!");

		return 0;

	}

	//count the number of points to copy

	unsigned pointCount = 0;

	{

		for (unsigned i=0; i<count; ++i)

			if (m_pointsVisibility->getValue(i) == POINT_VISIBLE)

				++pointCount;

	}

	if (pointCount == 0)

	{

		ccLog::Warning("[ccGenericPointCloud::getTheVisiblePoints] No point in selection");

		return 0;

	}

	//we create an entity with the 'visible' vertices only

	CCLib::ReferenceCloud* rc = new CCLib::ReferenceCloud(const_cast<ccGenericPointCloud*>(this));

	if (rc->reserve(pointCount))

	{

		for (unsigned i=0; i<count; ++i)

			if (m_pointsVisibility->getValue(i) == POINT_VISIBLE)

				rc->addPointIndex(i); //can't fail (see above)

	}

	else

	{

		delete rc;

		rc = 0;

		ccLog::Error("[ccGenericPointCloud::getTheVisiblePoints] Not enough memory!");

	}

	return rc;

}