docs: int countFeaturesWith3D(View v ) {
  
  		int count = 0;
  
  		for (int i = 0; i < v.connections.size(); i++) {
  			Motion m = v.connections.get(i);
  
  			boolean isSrc = m.viewSrc == v;
  
  			for (int j = 0; j < m.associated.size(); j++) {
  				AssociatedIndex a = m.associated.get(j);
  
  				if( isSrc ) {
  					count += m.viewDst.features3D[a.dst] != null ? 1 : 0;
  				} else {
  					count += m.viewSrc.features3D[a.src] != null ? 1 : 0;
  				}
  			}
  		}
  
  		return count;
  	}