Point cloud tools

This wiki present the base tools included in the Pointcloud plugin. The version used in 1.7.

Every tools presented here are available both from GUI or from RGG code. The projects used to create the images are available from the example explorer embedded in GroIMP. The tools consider the local transformation of the point cloud. The coordinate of the Point are local in relatively to the Point cloud Node.

See more:

• Point cloud structure
• Import/export point clouds

There are two GUI way for accessing the point clouds tools:

• The edit menu:

• The interactive toolbar (from the Coolbar plugin), which automatically display usable methods depending on the current selection. See here for more information.

In order to select several objects please hold the CTRL key while clicking on the objects.

To use the tools in RGG you should import the following packages:

import de.grogra.pointcloud.groimp.*;
import de.grogra.pointcloud.groimp.PointCloud;
import de.grogra.pointcloud.objects.impl.*;
import de.grogra.pointcloud.tools.Tools;

It is key to understand that in GroIMP each node have a local transformation, and the global coordinate of a node depends on the resolution of all previous local transformations from its parents in the graph.

For point clouds nodes, it means that two point clouds with points that have the SAME coordinates, might be displayed at different global coordinates. The coordinates of Points are local by default. For instance, the two following point clouds are imported from the same file (and thus have the same local coordinates):

The first image results from PointCloud F and the second from F PointCloud.

It is possible to force a point cloud to have global coordinates by moving it to the root of the graph and transforming it with its globalTransformation with :

PointCloud myPC = ...;
Matrix34d transfo = de.grogra.pointcloud.utils.Utils.getGlobalTransform( myPC);
Matrix4d localT = myPC.getLocalTransformation();
myPC.setTransform( transfo.transform( localT ) );
[c:PointCloud ==> ^c;]

A given point cloud can be split into two point clouds based on a plane object.

The function requires the selection of a plane and a point cloud (in that order!). If the splitting was successful, both point clouds are selected afterwards. If the plane did not cut the point cloud, one of the new point clouds remains empty.

in RGG the split function from the tools class can be used. This class returns a cloud array with the old and the new cloud. The new one has to be added to the graph afterwards.

public void splitByPlane(){
 Cloud c = first((*PointCloud*)).getCloud();
 Plane p = first((*Plane*));
 Cloud[] clouds = de.grogra.pointcloud.tools.Tools.split(p, c);
 Cloud c2 =clouds[1];
 [
  ==>>^c2;
 ]
}

Note: The RGG split only works with a plane added through RGG

A selection of leafs (points) of a point cloud can be seperated to become their own point cloud.

Select first the cloud that holds the points and then the points that are suppose to be separated. after executing the function two point cloud appear.

The following example shows the usage of this tool on a CloudGraph:

public void splitByLeaf(){
// get the first Cloud object that handle LeafPoint object.
Cloud c = first((* pc:PointCloud, 
    (pc.getCloud() instanceof CloudGraph), 
    ( ((CloudGraph)pc.getCloud()).getChildrenType().isAssignableFrom( LeafPointImpl.class)  ) *)).getCloud(); 
 
//get the first three points found in the graph below the cloud root 
Cloud[] clouds = Tools.split(slice((*c.getNode() (-->)*LeafPointImpl*),0,3), c);
Cloud c2 =clouds[1];
[
  ==>>^c2;
]
}

Turning several point clouds into one. The end result will be of the format (graph/list/array) of the first selected point cloud.

The merge tool is considering the coordinate of the point relatively to the Point cloud Node. For Node added to the root of the project graph, their local transformations are equivalent to a global one. Thus, Point clouds added at the root of the project graph, or having not transforming parent to the root, have “global coordinate”.

However, if the point clouds are under other transformations in the graph, the merged Points will be added to the other Point cloud with their local coordinate.

Select all point clouds to merge and execute the merge command.

A simple way to merge all point clouds in RGG is to combine the tool with a query.

public void merge(){
 de.grogra.pointcloud.tools.Tools.merge(((*PontCloud*)));
 (*PontCloud*).update();
}

Additionally with Tools.merge(cloud ,cloud[]), it is possible to add all clouds form cloud[] to the given first cloud.

Point clouds added to the Project graph root:

Point clouds with local transformations (as part branch of Nodes with transformations). In the following example, the two point clouds are added each after a F build by the following code (where PC1 and PC2 are the Point cloud nodes:

Axiom ==> F PC1 F PC2 ;

In that example, the points of PC1 are translated by the F Node, but their local coordinates do not include this translation. Similarly, the points of PC2 are translated twice, once per F.

If we merge the RED point cloud (PC2) into the BLACK one we have the following result (the points of PC2 are translated only by the first F):

Basic K-means clustering

after selecting a point cloud and clustering it, the new created point clouds are added to the graph.

public void Kcluster(){
 BoundedCloud c = (BoundedCloud) first((* pc:de.grogra.pointcloud.groimp.PointCloud, 
    (pc.getCloud() instanceof BoundedCloud) *)).getCloud(); 
 Cloud[] res = de.grogra.pointcloud.tools.KMeans.cluster(c,2,4);
 for(Cloud y : res){
 [
  ==>>^y;
 ]
 }
}