As described earlier, pcl::PointCloud contains a field that serves as a container for the points; this field is of the PointT type, which is the template parameter of the pcl::PointCloud class and defines the type of point the cloud is meant to store. PCL defines many types of points, but a few of the most commonly used ones are the following:
- pcl::PointXYZ: This is the simplest type of point and probably one of the most used; it stores only 3D XYZ information.
- pcl::PointXYZI: This type of point is very similar to the previous one, but it also includes a field for the intensity of the point. Intensity can be useful when obtaining points based on a certain level of return from a sensor. There are two other standard identical point types to this one—the first one ispcl::InterestPoint, which has a field to store strength instead of intensity, and pcl::PointWithRange, which has a field to store the range instead of either intensity or strength.
- pcl::PointXYZRGBA: This type of point stores 3D information as well as color (RGB: red, green, blue) and transparency (A: alpha).
- pcl::PointXYZRGB: This type is similar to the previous point type, but it differs in that it lacks the transparency field.
- pcl::Normal: This is one of the most used types of points; it represents the surface normal at a given point and a measure of its curvature.
- pcl::PointNormal: This type is exactly the same as the previous one; it contains the surface normal and curvature information at a given point, but it also includes the 3D XYZ coordinates of the point. Variants of this point are PointXYZRGBNormal and PointXYZINormal, which, as the names suggest, include color (former) and intensity (latter).
Aside from these common types of points, there are many more standard PCL types, such as PointWithViewpoint, MomentInvariants, Boundary, PrincipalCurvatures, and Histogram. More importantly, the PCL algorithms are all converted to templates so that not only the available types can be used, but also semantically valid user-defined types can be used.