Openni pointcloud

In the simple openni example, pointcloud draw on user tracking
for example:
ofxOpenNIUser user;
user.drawpointcloud;

how can i draw pointcloud of the fool scene? i known that i must use something like : openNIDevices[deviceID].addDepthThreshold(nearThreshold,farThreshold);
but what then? how can i get x.y.z? how can i get a mesh?