PCLVisualizer: save and restore camera information

[xiangxw]

Press ctrl + s to save camera parameters and ctrl + r to restore the
saved camera parameters.

If a camera file is specified with "-cam" option or pcd file(s) is(are)
available in the command line, the camera parameters will be written to
the corresponding file and can be restored later from that file.
In this case, PCLVisualizer will restore camera parameters automatically
from the corresponding file when the pragram restarts with the same
command line input.

[xiangxw]

Origin camera:

Change camera and press ctrl + s to save the camera information:

Restarted:

[taketwo]

I think this is a very useful contribution, thanks! I have a few comments though:

• In PCLVisualizer we already have functions to save/load camera parameters. Would be nice to reuse them to make sure that the file format is consistent.
• I am not sure if ".screenshot-%s.cam" is a good filename. Why screenshot? Why hidden?
• What about providing another shortcut to load camera information on demand? For example, the user might open the scene, play around selecting a good view, save it, then move the camera around even more in an attempt to find a better view. Then he decides that the first saved view was better, and reloads it.

[xiangxw]

hi, @taketwo

• I can't find any public functions in PCLVisualizer to save/load camera parameters. My code is copyed from interactor_style.cpp, there is no public api there. Is it ok to add this extension to PCLVisualizer so that every PCLVisualizer has this ability?
• There may be multiple .pcd files for pcl_viewer to view so we name the .cam file with sha1(not pathes of the .pcd files. And sha1 filename is hard to understand, so we make it hidden. Users do not need to see the .cam file.
• Good idea. I will do that.

Question: If I add this to PCLVisualizer, path of .pcd files are not available so sha1 can be calculated. Any idea about how to calculate sha1 value of pointclouds? Thanks.

[taketwo]

• The ultimate goal should be to have a single implementation of saving/loading so that different clients can call it. If this could be put in PCLVisualizer, then why not.
• I very much like the idea with SHA1, and you are right that the names are a bit unreadable. But still, why putting "screenshot" inside the name?
• What shortcuts do you think it makes sense to assign to saving/loading?

Question: If I add this to PCLVisualizer, path of .pcd files are not available so sha1 can be calculated.

I would rather have save/load functions that take a filename. It's up to the client (pcl_viewer in our case) how it constructs this name.

[xiangxw]

hi, @taketwo

• I will put this in PCLVisualizer.
• "screenshot" is from interactor_style.cpp and I will remove it, with ".%s.cam" remaining.
• How about ctrl+s for saving and ctrl+r for restoring?

PCLVisualizer will read "-cam" option and filenames from command arguments, and I will pass sha1 value of .pcd paths to PCLVisualizerInteractorStyle which is attached to the PCLVisualizer

[taketwo]

How about ctrl+s for saving and ctrl+r for restoring?

+1

PCLVisualizer will read "-cam" option and filenames from command arguments

I am not sure I understand what you mean here.

[xiangxw]

@taketwo Sorry for my english.
I mean I will modify constructor:

 PCLVisualizer (int &argc, char **argv, const std::string &name="", PCLVisualizerInteractorStyle *style=PCLVisualizerInteractorStyle::New(), const bool create_interactor=true)

to calculate sha1 value and pass it to PCLVisualizerInteractorStyle. If "-cam" option are valid, camera information will save/restore using the specified .cam file

[taketwo]

What about the following use-case. I have a program that uses PCLVisualizer to display some point clouds that it creates at runtime. This means that when it instantiates PCLVisualizer, it does not pass any filenames to it. Rather the point clouds are added programmatically later on. How saving/loading of camera parameters may be organized in this case?

[xiangxw]

@taketwo
In this case, camera information will be written to memory, not .cam file. Camera information can be restored using the information from memory, but can't be restored when program restarts,

[taketwo]

Why this restriction? Wouldn't it make sense to have PCLVisualizer::saveCameraParameters (const std::string& filename) so that we can store the viewpoint to an arbitrary file?

[xiangxw]

Great @taketwo I will do that

[xiangxw]

Tested cases:

• Test case 1: single input .pcd file.

  ./bin/pcl_viewer kitchen_small_1_1.pcd

• Test case 2: multiple input .pcd files.

  ./bin/pcl_viewer kitchen_small_1_1.pcd kitchen_small_1_2.pcd

• Test case 3: with "-cam" option.

  ./bin/pcl_viewer kitchen_small_1_1.pcd kitchen_small_1_2.pcd -cam 14.2608,2660.28/0,0,1/985.715,-401.162,909.226/0.288812,0.951412,0.106784/0.8575/960,540/603,242

• Test case 4: with "-cam" option(camera file).

  ./bin/pcl_viewer kitchen_small_1_1.pcd kitchen_small_1_2.pcd -cam .efe7509f521e5435dc6008d38d927fd321ad30a0.cam

• Test case 5: restart program(camera file saved will be automatically loaded).

[xiangxw]

Hi, @taketwo Is it ok to merge?

[taketwo]

@xiangxw I skimmed through the code already and have a couple of questions. But in order to formulate them properly I would need some more time to dig in and read carefully. Unfortunately I'm quite busy with other things at the moment. I will come back to your PR as soon as possible. Sorry.

[xiangxw]

@taketwo ok, thanks.

[taketwo]

I think "save" is not a correct verb here. It has connotations with persistence and disk I/O. Rather, here the current camera parameters are retrieved into a variable. I would definitely call this getCameraParameters().

[xiangxw]

yes, you are right.

[xiangxw]

Hi @taketwo I have modified the code. Thanks.

[taketwo]

Looks good to me now, though I have one question. How is this going to behave in the following situation? Suppose the user provided -cam option when starting viewer. Camera parameters will be loaded from the specified file. But later on, when saving and restoring with 'Ctrl-S'/'Ctrl-R', will the parameters be saved/loaded to that same file? I think it would make sense if it was so. The user kind of suggesting that he wants to work with some particular camera file, not a "random" one.

[xiangxw]

hi @taketwo

• When -cam is provided with a camera file, the camera parameters will be saved to/loaded from that same file.
• When -cam is provided with camera parameters, the camera parameters will be saved to/loaded from memory.

[taketwo]

Great, that is exactly the behavior I was thinking about.

So everything is fine from my viewpoint. @jspricke?