is_dense not properly set when loading PLY files

[VictorLamoine]

is_dense is wrongly set to false when loading a PLY cloud (reported here and here).
This line is responsible: io/src/ply_io.cpp#L62

Is must be set to true, and when adding vertex the variable should be set to false if one of the components is not finite.

Test code:
#1433

It should be tested within PCL:
#1381 (comment)

[SergioRAgostinho]

👍 When you submit the PR for this can you please uncomment the lines in the color test?

[VictorLamoine]

Ok but I'm not sure how should I check if the values are finite or not, I see 2 options:

• Just before returning the ply loading function, loop through the cloud and search for non-finite values. Dumb & slow but easy to implement.
• When parsing the values, if one is non-finite, change is_dense to false.

The scalar values are parsed here but I don't see an easy way to modify the is_dense property from here, it requires modifying the function signature.

[jspricke]

Can't we check it in the global loop? I guess it's this one: https://github.com/PointCloudLibrary/pcl/blob/master/io/src/ply_io.cpp#L603

[VictorLamoine]

We only go into this loop if the PLY file has the range_grid field.

[SergioRAgostinho]

@VictorLamoine Notice that at some point, the value inferred in here needs to be stored on the pointcloud/blob. That happens further ahead, probably in whatever get's called in here.
Look at scalarPropertyDefinitionCallback and "friends" in ply_io.cpp. Eventually you'll find the callback which store the value on the cloud/blob. Sorry for not being precise, but I'm not on my development pc at the moment.

[SergioRAgostinho]

I have the impression it takes place here.

Now the question for me is, under which conditions do you set is_dense to false? I know it happens when one of the coordinates from a point is set to NaN. Is this also valid for any other (float) scalar, one might need to parse, e.g. a normal? What happens if your scalar value is Inf?

[VictorLamoine]

Yes it's exactly here, using pcl_isfinite works fine, I've just compiled PCL with that and it works;

    if (!pcl_isfinite (value))
      cloud_->is_dense = false;

I was about to ask the same question, the documentation is not very clear about this:
http://docs.pointclouds.org/trunk/classpcl_1_1_point_cloud.html#a3ca88d8ebf6f4f35acbc31cdfb38aa94

If the color is invalid, should we set the point cloud to non dense? Etc.