I confirmed that a user-defined point type described in
http://www.ros.org/wiki/pcl_ros worked well for our purpose.

I have a question for using a user-defined point type.
PointXYZRGB defined in point_types.hpp is using PCL_ADD_POINT4D,
EIGEN_ALIGNE16.
I tested simple user-defined class not using EIGEN_ALIGN16 and
a user-defined class added 'category' to PointXYZRGB.
Both classes worked well.
Which is the recommended / correct way for using a user-defined class?

* test code

---
namespace my_ns
{
#if 0
  struct PointXYZRGBClass
 {
   float x;
   float y;
   float z;
   float rgb;
   uint32_t category;
  };
#else
  struct PointXYZRGBClass
  {
    PCL_ADD_POINT4D;  // This adds the members x,y,z which can also be
accessed using the point (which is float[4])
    float rgb;
    uint32_t category;
    EIGEN_MAKE_ALIGNED_OPERATOR_NEW
  } EIGEN_ALIGN16;
#endif
} // namespace my_ns

POINT_CLOUD_REGISTER_POINT_STRUCT
(my_ns::PointXYZRGBClass,
 (float, x, x)
 (float, y, y)
 (float, z, z)
 (float, rgb, rgb)
 (uint32_t, category, category)
 );

2011/1/24 Kei Okada <k-okada@jsk.t.u-tokyo.ac.jp>:
>> Frequently, these problems are better solved by republishing some or
>> all of the original points as a single PointCloud2 with a
>> categorization field. The data can be sorted on that field for
>> efficient access, sometimes that occurs naturally as a result of your
>> algorithm, anyway.
>
> I see, that's seems good solution.
>
> Just to be clear, your suggestion is to make PointCloud2 data as followings.
>    sensor_msgs::PointCloud2 cloud2_;
>    cloud2_.fields.resize( 5 );
>    cloud2_.fields[0].name = "x";
>    cloud2_.fields[1].name = "y";
>    cloud2_.fields[2].name = "z";
>    cloud2_.fields[3].name = "rgb";
>    cloud2_.fields[3].name = "label" or "category";
> if this is correct, is there a way to convert from/to pcl::Point*** ??
> Usually, we will write program using pcll:PointCloud<pcl::PointXYZRGB>...
>
>
> On Sun, Jan 23, 2011 at 2:43 AM, Jack O'Quin <jack.oquin@gmail.com> wrote:
>> On Fri, Jan 21, 2011 at 7:32 AM, cmuell2s
>> <christian.mueller@smail.inf.fh-bonn-rhein-sieg.de> wrote:
>>> Hello all,
>>>
>>> I stuck at a small problem. I would like to publish a vector/array of
>>> pcl::PointCloud<pcl::PointXYZ>.
>>> I couldn't find a sensor_msg or std_msg which would do it, did I
>>> overlooked sth?
>>
>> This comes up frequently. In many cases it seems the obvious solution.
>>
>> Often, problems become apparent on further consideration: who will
>> read this vector of pointclouds? What operations must be performed on
>> it?
>>
>> Frequently, these problems are better solved by republishing some or
>> all of the original points as a single PointCloud2 with a
>> categorization field. The data can be sorted on that field for
>> efficient access, sometimes that occurs naturally as a result of your
>> algorithm, anyway.
>> --
>>  joq
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>>
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