[PCL]ApproximateVoxelGrid

点云滤波继承自Filter模板类

注意Filter类的filter 方法调用了虚方法applyFilter：

inline void  filter (PointCloud &output)
      {
        if (!initCompute ())
          return;

        if (input_.get () == &output)  // cloud_in = cloud_out
        {
          PointCloud output_temp;
          applyFilter (output_temp);
          output_temp.header = input_->header;
          output_temp.sensor_origin_ = input_->sensor_origin_;
          output_temp.sensor_orientation_ = input_->sensor_orientation_;
          pcl::copyPointCloud (output_temp, output);
        }
        else
        {
          output.header = input_->header;
          output.sensor_origin_ = input_->sensor_origin_;
          output.sensor_orientation_ = input_->sensor_orientation_;
          applyFilter (output);
        }

        deinitCompute ();
      }

ApproximateVoxelGrid进行点云Filter

效果图：

原始点云66901个点，点云平均距离0.038253，采样参数（Grid size 0.2）后点云数目11924