CloudCompare forum

Posted: **Wed Mar 13, 2019 1:46 pm**

Hello everyone!

I'm trying to implement the "Compute cloud/cloud distance" in a Qt project. I have been able to run the ccViewer in Qt. and, also, I'm capable of visualize clouds dropped on the viewer window or from a file read in the code.

My main problem is that, when I compute the distances, I get a mean distance and deviaton of zero. I also have to resize the clouds in order to avoid errors. It's like the ccPointCloud doesn't have any points even though the reading function returns CC_FERR_NO_ERROR and the cloud it's correctly displayed.

I leave here the function I have made to read the .asc files and get the information in a ccHObject.

Code: Select all

CC_FILE_ERROR readASCPointCloud(QString path, ccHObject &container, ccViewer* widget)
{
    AsciiFilter *mFilter= new AsciiFilter;
    CCVector3d loadCoordinatesShift(0,0,0);
    bool loadCoordinatesTransEnabled = true;
    FileIOFilter::LoadParameters mParam;
    {
            mParam.alwaysDisplayLoadDialog = false;//true to see the window
            mParam.shiftHandlingMode = ccGlobalShiftManager::DIALOG_IF_NECESSARY;
            mParam.coordinatesShift = &loadCoordinatesShift;
            mParam.coordinatesShiftEnabled = &loadCoordinatesTransEnabled;
            mParam.parentWidget = widget;
    }

    return mFilter->loadFile(path,container, mParam);
}

Also, here is the chunk of code where I read the files, convert the clouds to ccPointCloud and compute the distances.

Code: Select all

...
ccViewer w;
...
 //Reading the Ascii files
ccHObject* comp_example=ccHObject::New(CC_TYPES::POINT_CLOUD);
CC_FILE_ERROR read_comp;
read_comp=readASCPointCloud(path1, *comp_example, &w);

ccHObject* src_example=ccHObject::New(CC_TYPES::POINT_CLOUD);
CC_FILE_ERROR read_ref;
read_ref=readASCPointCloud(path2, *src_example, &w);

//Casting
ccPointCloud* compCloud = ccHObjectCaster::ToPointCloud(comp_example);
ccPointCloud* srcCloud = ccHObjectCaster::ToPointCloud(src_example);
                 
//Display in viewer
w.addToDB(srcCloud);
w.addToDB(compCloud);

//Avoiding error -1
compCloud->resize(80589); 
srcCloud->resize(80589);

//Computing distances
w.ComputePointCloudDistances(compCloud, srcCloud);
w.addToDB(compCloud);

When I debug I get that, after the casting, the cloud is apparently empty even though is displayed in the viewer without problem.

: error.png (132.73 KiB) Viewed 26324 times

Does anyone know what I'm doing wrong? Any kind of help will be useful.

Thanks in advance!
Álvaro

Posted: **Wed Mar 13, 2019 8:10 pm**

comp_example is a ccHObject instance (a 'group' object). You cannot convert it to a point cloud directly.

You have to look for its children (normally there should only be one if you load an ASCII file) and this child should be a point cloud. Pay attention that ccHObjectCaster::ToPointCloud may return a null pointer (if the input entity cannot be converted to a point cloud).

Posted: **Wed Mar 13, 2019 8:13 pm**

And if the cloud is empty, it's for a reason. No need to 'resize' it to make the function 'work'. As there will be no valid point in such a cloud.

Posted: **Wed Mar 13, 2019 11:19 pm**

daniel wrote: ↑Wed Mar 13, 2019 8:10 pm comp_example is a ccHObject instance (a 'group' object). You cannot convert it to a point cloud directly.

You have to look for its children (normally there should only be one if you load an ASCII file) and this child should be a point cloud. Pay attention that ccHObjectCaster::ToPointCloud may return a null pointer (if the input entity cannot be converted to a point cloud).

Thanks! I was sure that i have tested with getting childs from the ccHObject but there must have been other mistakes when I tried. Now I'm dealing with some errors in the cloud2cloud distance calculation but, at least, my clouds have some points!

daniel wrote: ↑Wed Mar 13, 2019 8:13 pm And if the cloud is empty, it's for a reason. No need to 'resize' it to make the function 'work'. As there will be no valid point in such a cloud.

Yeah, I know it doesn't have much sense but after a couple of hours trying to solve it I started to think that there was a kind of bug. It was more like something I did to debug. Sorry for including it in the posted code.

Thank you again!

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