[ros-users] PCL nodelet PointCloudConcatenateFieldsSynchronizer

[Felix Ruess]

Hi Radu,

thanks for the quick reply.


On Wed, Sep 29, 2010 at 8:46 PM, Radu Bogdan Rusu <rusu at willowgarage.com> wrote:
> Dear Felix,
>
> On 09/29/2010 11:39 AM, Felix Ruess wrote:
>>
>> Hi,
>>
>> I'm using the pcl::concatenateFields(cloud_a, cloud_b, cloud_out)
>> function to concatenate
>>   pcl::PointCloud<pcl::PointXYZ>  cloud_a;
>>   pcl::PointCloud<pcl::Normal>  cloud_b;
>> to
>>   pcl::PointCloud<pcl::PointNormal>  cloud_out;
>> and it works great!
>
> Thanks! We're happy to hear that.
>
>
>> Is there any possibility to specify the output cloud type for the
>> nodelet pcl/PointCloudConcatenateFieldsSynchronizer somehow as well?
>> (This is used in the normal estimation launch file for example).
>
> By output cloud type you mean you want to copy only certain fields, and not
> all? That is, if you have
>
> PointCloud<PointXYZ> a;
> PointCloud<Normal> b;
>
> you want
> PointCloud<PointXYNormal> c
> instead of
> PointCloud<PointXYZNormal> c
>
> ?

No, not quite.
I just want to solve the problem that when I concatenate PointXYZ and
Normal (using the nodelet) I get a message that I can then convert
back to pcl PointNormal.
This fails because PointNormal is padded with the field w to be SSE friendly.
As long as the fields are simply concatenated there is no "magic"
happening to make sure I can convert it back to an already existing
pointcloud type (e.g. PointNormal).


>> The problem I have with the nodelet is that I'm trying to convert the
>> output pointcloud2 message to
>>     struct PointNormal;
>>     // Members: float x, y, z; uint32_t w; float normal[3], curvature;
>> to read the data.
>> Now of course this does not work as the padding w is missing from the
>> output pointcloud2 message I get from the nodelet since it "only"
>> concatenates the existing fields of the input clouds.
>>
>> So, is there some way to adapt the nodelet to output a pointcloud2
>> message that corresponds to a specific pcl PointCloud<specified point
>> type>?
>
> In general yes, we've been working on making that possible by publishing
> pcl::PointCloud<T> types instead of sensor_msgs::PointCloud2 types. However,
> that's not fully finished yet (CC-ing Patrick who is the mastermind behind
> all that magic).


Yes, I guess that would potentially solve the problem as it then would
be easier to write a new nodelet where you can specify the template
type for the output cloud (or even uses the concatenateFields
function).


>> P.S. I did not sent this to pcl-users because the nodelet lives in pcl_ros
>
> You can definitely send it there as pcl-users@ deals both with PCL _and_
> PCL_ROS. :)
>
> Cheers,
> Radu.

:-)

Cheers, Felix