无法进入优化步骤，报错[pcl::KdTreeFLANN::setInputCloud] Cannot create a KDTree with an empty input cloud!

[Goughhhhhh]

运行自己的录制的数据（Livox Avia录制的pcd点云和D4354i录制640×480分辨率的影像）时报错：[pcl::KdTreeFLANN::setInputCloud] Cannot create a KDTree with an empty input cloud!

导致无法进入优化程序，具体表现为没有输出点云-图像残差图以及没有点云叠加的优化窗口，如下图所示：


排除了点云路径错误、点云话题名称错误以及点云密度过于稀疏等#19 Issue和#84 Issue中提到的可能的错误，即能读取并在rviz上显示就说明点云路径和话题名称没错，能提取到足够多的线特征（红色的线条）就说明点云密度达到标定要求（为此我还对比了项目demo中3.pcd的点云密度，我采集的点云数量远高于demo中的点云数量），如下图所示。但是问题依然没有得到解决。

当我把D435i的影像分辨率改为和作者demo中提供的影像分辨率1920×1080，并在相同环境、相同位置录制数据后，程序正常运行了！请问作者和各位大佬们，这可能是什么问题？如果想用640×480分辨率的影像进行标定，我该怎么做？
回复为盼。祝大家好！

[tdcsu]

First, I fixed the livox avia at a certain location,
then I ran the fast_lio to get a denser registration of pointcloud.
At the same time, the images from a sub_cam with resolution 640x480 were recored.
After that, I ran the calibration based on the last frame image and the cloud registration, and successfully get a not bad result.

As you can see from the figures below, the topleft is the color_pcd, the bottom is the cloud regidtration by fast_lio based on livox avia, and the right is the image from usb_cam.

Here is my senser setup:

[tdcsu]

First, I fixed the livox avia at a certain location, then I ran the fast_lio to get a denser registration of pointcloud. At the same time, the images from a sub_cam with resolution 640x480 were recored. After that, I ran the calibration based on the last frame image and the cloud registration, and successfully get a not bad result.

As you can see from the figures below, the topleft is the color_pcd, the bottom is the cloud regidtration by fast_lio based on livox avia, and the right is the image from usb_cam. Here is my senser setup:

so i think if the density of your point cloud is not enough.