camera_chain_sensor.py
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00032 
00033 # author: Vijay Pradeep
00034 
00035 # Define a camera sensor attached to a chain
00036 #
00037 #       before_chain_Ts -- camera_chain -- after_chain_Ts -- camera
00038 #      /
00039 #   root
00040 #      \
00041 #       checkerboard
00042 
00043 import numpy
00044 from numpy import matrix, reshape, array, zeros, diag, real
00045 
00046 import roslib; roslib.load_manifest('calibration_estimation')
00047 import rospy
00048 from calibration_estimation.full_chain import FullChainRobotParams
00049 from sensor_msgs.msg import JointState
00050 
00051 class CameraChainBundler:
00052     """
00053     Tool used to generate a list of CameraChain sensors from a single calibration sample message
00054     """
00055     def __init__(self, valid_configs):
00056         self._valid_configs = valid_configs
00057 
00058     # Construct a CameraChainSensor for every camera chain sensor that exists in the given robot measurement
00059     def build_blocks(self, M_robot):
00060         """
00061         Input:
00062         - M_robot: A calibration sample of type calibration_msgs/RobotMeasurement
00063         Returns:
00064         - sensors: A list of CameraChainSensor objects that corresponds to all camera chain sensors found
00065                    in the calibration message that was passed in.
00066         """
00067         sensors = []
00068         for cur_config in self._valid_configs:
00069             if cur_config["sensor_id"] in [ x.camera_id for x in M_robot.M_cam ]:
00070                 if "chain_id" in cur_config.keys() and cur_config["chain_id"] != None and cur_config["chain_id"] != "NONE":
00071                     if cur_config["chain_id"] in [ x.chain_id  for x in M_robot.M_chain ] :
00072                         M_cam   = M_robot.M_cam  [ [ x.camera_id for x in M_robot.M_cam   ].index(cur_config["sensor_id"])]
00073                         M_chain = M_robot.M_chain[ [ x.chain_id  for x in M_robot.M_chain ].index(cur_config["chain_id"]) ]
00074                         if cur_config["frame_id"] != M_cam.cam_info.header.frame_id:
00075                             rospy.logwarn('WARNING frame_id of cam_info.header.frame_id({}) from bag file'.format(M_cam.cam_info.header.frame_id))
00076                             rospy.logwarn('        and sensors.rectified_cams.{}.frame_id({}) of system.yaml differ'.format(cur_config["chain_id"],cur_config["frame_id"]))
00077                     else:
00078                         continue
00079                 else:
00080                     M_cam   = M_robot.M_cam  [ [ x.camera_id for x in M_robot.M_cam   ].index(cur_config["sensor_id"])]
00081                     M_chain = None
00082                     cur_config["chain_id"] = None
00083                 cur_sensor = CameraChainSensor(cur_config, M_cam, M_chain)
00084                 sensors.append(cur_sensor)
00085             else:
00086                 rospy.logdebug("  Didn't find block")
00087         return sensors
00088 
00089 class CameraChainSensor:
00090     def __init__(self, config_dict, M_cam, M_chain):
00091         """
00092         Generates a single sensor block for a single configuration
00093         Inputs:
00094         - config_dict: The configuration for this specific sensor. This looks exactly like
00095                        a single element from the valid_configs list passed into CameraChainBundler.__init__
00096         - M_cam: The camera measurement of type calibration_msgs/CameraMeasurement
00097         - M_chain: The chain measurement of type calibration_msgs/ChainMeasurement
00098         """
00099         self.sensor_type = "camera"
00100         self.sensor_id = config_dict["sensor_id"]
00101 
00102         self._config_dict = config_dict
00103         self._M_cam = M_cam
00104         self._M_chain = M_chain
00105 
00106         self._full_chain = FullChainRobotParams(config_dict["chain_id"], config_dict["frame_id"])
00107 
00108         self.terms_per_sample = 2
00109         if "baseline_rgbd" in config_dict.keys():
00110             self.terms_per_sample = 3
00111 
00112     def update_config(self, robot_params):
00113         """
00114         On each optimization cycle the set of system parameters that we're optimizing over will change. Thus,
00115         after each change in parameters we must call update_config to ensure that our calculated residual reflects
00116         the newest set of system parameters.
00117         """
00118         self._camera = robot_params.rectified_cams[ self.sensor_id ]
00119         if self._full_chain is not None:
00120             self._full_chain.update_config(robot_params)
00121 
00122     def compute_residual(self, target_pts):
00123         """
00124         Computes the measurement residual for the current set of system parameters and target points
00125         Input:
00126         - target_pts: 4XN matrix, storing features point locations in world cartesian homogenous coordinates.
00127         Output:
00128         - r: terms_per_sample*N long vector, storing pixel residuals for the target points in the form of
00129              [u1, v1, u2, v2, ..., uN, vN] or [u1, v1, u'1, u2....]
00130         """
00131         z_mat = self.get_measurement()
00132         h_mat = self.compute_expected(target_pts)
00133         r = array(reshape(h_mat - z_mat, [-1,1]))[:,0]
00134         return r
00135 
00136     def compute_residual_scaled(self, target_pts):
00137         """
00138         Computes the residual, and then scales it by sqrt(Gamma), where Gamma
00139         is the information matrix for this measurement (Cov^-1).
00140         """
00141         r = self.compute_residual(target_pts)
00142         gamma_sqrt = self.compute_marginal_gamma_sqrt(target_pts)
00143         r_scaled = gamma_sqrt * matrix(r).T
00144         return array(r_scaled.T)[0]
00145 
00146     def compute_marginal_gamma_sqrt(self, target_pts):
00147         """
00148         Calculates the square root of the information matrix for the measurement of the
00149         current set of system parameters at the passed in set of target points.
00150         """
00151         import scipy.linalg
00152         cov = self.compute_cov(target_pts)
00153         gamma = matrix(zeros(cov.shape))
00154         num_pts = self.get_residual_length()/self.terms_per_sample
00155 
00156         for k in range(num_pts):
00157             first = self.terms_per_sample*k
00158             last = self.terms_per_sample*k+self.terms_per_sample
00159             sub_cov = matrix(cov[first:last, first:last])
00160             sub_gamma_sqrt_full = matrix(scipy.linalg.sqrtm(sub_cov.I))
00161             sub_gamma_sqrt = real(sub_gamma_sqrt_full)
00162             assert(scipy.linalg.norm(sub_gamma_sqrt_full - sub_gamma_sqrt) < 1e-6)
00163             gamma[first:last, first:last] = sub_gamma_sqrt
00164         return gamma
00165 
00166     def get_residual_length(self):
00167         return self.terms_per_sample*len(self._M_cam.image_points)
00168 
00169     def get_measurement(self):
00170         """
00171         Get the target's pixel coordinates as measured by the actual sensor
00172         """
00173         if self.terms_per_sample == 2:
00174             return numpy.matrix([[pt.x, pt.y] for pt in self._M_cam.image_points])
00175         elif self.terms_per_sample == 3:
00176             return numpy.matrix([[pt.x, pt.y, self._camera.get_disparity(self._M_cam.cam_info.P, pt.z)] for pt in self._M_cam.image_points])
00177 
00178     def compute_expected(self, target_pts):
00179         """
00180         Compute the expected pixel coordinates for a set of target points.
00181         target_pts: 4xN matrix, storing feature points of the target, in homogeneous coords
00182         Returns: target points projected into pixel coordinates, in a Nx2 matrix
00183         """
00184         if self._M_chain is not None:
00185             return self._compute_expected(self._M_chain.chain_state, target_pts)
00186         else:
00187             return self._compute_expected(None, target_pts)
00188     def _compute_expected(self, chain_state, target_pts):
00189         """
00190         Compute what measurement we would expect to see, based on the current system parameters
00191         and the specified target point locations.
00192 
00193         Inputs:
00194         - chain_state: The joint angles of this sensor's chain of type sensor_msgs/JointState.
00195         - target_pts: 4XN matrix, storing features point locations in world cartesian homogenous coordinates.
00196 
00197         Returns: target points projected into pixel coordinates, in a Nx2 matrix
00198         """
00199         # Camera pose in root frame
00200         camera_pose_root = self._full_chain.calc_block.fk(chain_state)
00201         cam_frame_pts = camera_pose_root.I * target_pts
00202         # Do the camera projection
00203         pixel_pts = self._camera.project(self._M_cam.cam_info.P, cam_frame_pts)
00204         return pixel_pts.T
00205 
00206     def compute_expected_J(self, target_pts):
00207         """
00208         The output Jacobian J shows how moving target_pts in cartesian space affects
00209         the expected measurement in (u,v) camera coordinates.
00210         For n points in target_pts, J is a 2nx3n matrix
00211         Note: This doesn't seem to be used anywhere, except maybe in some drawing code
00212         """
00213         epsilon = 1e-8
00214         N = len(self._M_cam.image_points)
00215         Jt = zeros([N*3, N*self.terms_per_sample])
00216         for k in range(N):
00217             # Compute jacobian for point k
00218             sub_Jt = zeros([3,self.terms_per_sample])
00219             x = target_pts[:,k].copy()
00220             f0 = self.compute_expected(x)
00221             for i in [0,1,2]:
00222                 x[i,0] += epsilon
00223                 fTest = self.compute_expected(x)
00224                 sub_Jt[i,:] = array((fTest - f0) / epsilon)
00225                 x[i,0] -= epsilon
00226             Jt[k*3:(k+1)*3, k*self.terms_per_sample:(k+1)*self.terms_per_sample] = sub_Jt
00227         return Jt.T
00228 
00229     def compute_cov(self, target_pts):
00230         '''
00231         Computes the measurement covariance in pixel coordinates for the given
00232         set of target points (target_pts)
00233         Input:
00234          - target_pts: 4xN matrix, storing N feature points of the target, in homogeneous coords
00235         '''
00236         cam_cov = matrix(zeros([self.get_residual_length(), self.get_residual_length()]))
00237 
00238         # Convert StdDev into variance
00239         var_u = self._camera._cov_dict['u'] * self._camera._cov_dict['u']
00240         var_v = self._camera._cov_dict['v'] * self._camera._cov_dict['v']
00241         for k in range(cam_cov.shape[0]/self.terms_per_sample):
00242             cam_cov[self.terms_per_sample*k  , self.terms_per_sample*k]   = var_u
00243             cam_cov[self.terms_per_sample*k+1, self.terms_per_sample*k+1] = var_v
00244             if self.terms_per_sample == 3:
00245                 cam_cov[self.terms_per_sample*k+2, self.terms_per_sample*k+2] = self._camera._cov_dict['x'] * self._camera._cov_dict['x']
00246 
00247         # Both chain and camera covariances are now in measurement space, so we can simply add them together
00248         if self._M_chain is not None:
00249             return self.get_chain_cov(target_pts) + cam_cov
00250         else:
00251             return cam_cov
00252 
00253     def get_chain_cov(self, target_pts, epsilon=1e-8):
00254         num_joints = len(self._M_chain.chain_state.position)
00255         Jt = zeros([num_joints, self.get_residual_length()])
00256 
00257         x = JointState()
00258         x.position = self._M_chain.chain_state.position[:]
00259 
00260         # Compute the Jacobian from the chain's joint angles to pixel residuals
00261         f0 = reshape(array(self._compute_expected(x, target_pts)), [-1])
00262         for i in range(num_joints):
00263             x.position = [cur_pos for cur_pos in self._M_chain.chain_state.position]
00264             x.position[i] += epsilon
00265             fTest = reshape(array(self._compute_expected(x, target_pts)), [-1])
00266             Jt[i] = (fTest - f0)/epsilon
00267         cov_angles = [x*x for x in self._full_chain.calc_block._chain._cov_dict['joint_angles']]
00268 
00269         # Transform the chain's covariance from joint angle space into pixel space using the just calculated jacobian
00270         return matrix(Jt).T * matrix(diag(cov_angles)) * matrix(Jt)
00271         
00272     def build_sparsity_dict(self):
00273         """
00274         Build a dictionary that defines which parameters will in fact affect this measurement.
00275 
00276         Returned dictionary should be of the following form:
00277           transforms:
00278             my_transformA: [1, 1, 1, 1, 1, 1]
00279             my_transformB: [1, 1, 1, 1, 1, 1]
00280           chains:
00281             my_chain:
00282               gearing: [1, 1, ---, 1]
00283           rectified_cams:
00284             my_cam:
00285               baseline_shift: 1
00286               f_shift: 1
00287               cx_shift: 1
00288               cy_shift: 1
00289         """
00290         sparsity = self._full_chain.build_sparsity_dict()
00291         sparsity['rectified_cams'] = {}
00292         sparsity['rectified_cams'][self.sensor_id] = dict( [(x,1) for x in self._camera.get_param_names()] )
00293         return sparsity
00294 


calibration_estimation
Author(s): Vijay Pradeep, Michael Ferguson
autogenerated on Wed Aug 26 2015 10:56:21