[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