docs: private boolean checkBehindCamera(SceneStructureMetric structure ) {
  
  		int totalBehind = 0;
  		Point3D_F64 X = new Point3D_F64();
  		for (int i = 0; i < structure.points.length; i++) {
  			structure.points[i].get(X);
  			if( X.z < 0 )
  				totalBehind++;
  		}
  
  		if( verbose != null ) {
  			verbose.println("points behind "+totalBehind+" / "+structure.points.length);
  		}
  
  		return totalBehind > structure.points.length/2;
  	}