def _parse_cameras(input_file, num_cameras, camera_calibration_matrix):
# VisualSFM CAMERA coordinate system is the standard
# CAMERA coordinate system in computer vision
# (not the same as in computer graphics like in bundler, blender, etc.)
# That means
# the y axis in the image is pointing downwards (not upwards)
# the camera is looking along the positive z axis
# (points in front of the camera show a positive z value)
# The camera coordinate system in computer vision VISUALSFM
# uses camera matrices which are rotated around the x axis by 180 degree
# i.e. the y and z axis of the CAMERA MATRICES are inverted
# therefore, the y and z axis of the TRANSLATION VECTOR are also inverted
cameras = []
for camera_index in range(num_cameras):
line = input_file.readline()
# <Camera> = <File name> <focal length> <quaternion WXYZ> <camera center> <radial distortion> 0
line_values = line.split()
file_name = os.path.basename(line_values[0])
focal_length = float(line_values[1])
if camera_calibration_matrix is None:
camera_calibration_matrix = np.array([[focal_length, 0, 0],
[0, focal_length, 0],
[0, 0, 1]])
quaternion_w = float(line_values[2])
quaternion_x = float(line_values[3])
quaternion_y = float(line_values[4])
quaternion_z = float(line_values[5])
quaternion = np.array(
[quaternion_w, quaternion_x, quaternion_y, quaternion_z],
dtype=float)
camera_center_x = float(line_values[6])
camera_center_y = float(line_values[7])
camera_center_z = float(line_values[8])
center_vec = np.array(
[camera_center_x, camera_center_y, camera_center_z])
radial_distortion = float(line_values[9])
zero_value = float(line_values[10])
assert (zero_value == 0)
current_camera = Camera()
# Setting the quaternion also sets the rotation matrix
current_camera.set_quaternion(quaternion)
# Set the camera center after rotation
# COMMENT FROM PBA CODE:
# older format for compability
# camera_data[i].SetQuaternionRotation(q); // quaternion from the file
# camera_data[i].SetCameraCenterAfterRotation(c); // camera center from the file
current_camera._center = center_vec
# set the camera view direction as normal w.r.t world coordinates
cam_view_vec_cam_coord = np.array([0, 0, 1]).T
cam_rotation_matrix_inv = np.linalg.inv(
current_camera.get_rotation_mat())
cam_view_vec_world_coord = cam_rotation_matrix_inv.dot(
cam_view_vec_cam_coord)
current_camera.normal = cam_view_vec_world_coord
translation_vec = compute_camera_coordinate_system_translation_vector(
center_vec, current_camera.get_rotation_mat())
current_camera._translation_vec = translation_vec
current_camera.set_calibration(camera_calibration_matrix,
radial_distortion)
current_camera.file_name = file_name
current_camera.camera_index = camera_index
cameras.append(current_camera)
return cameras
def parse_cameras(json_data):
views = json_data['views']
intrinsics = json_data['intrinsics']
extrinsics = json_data['extrinsics']
# Remark: extrinsics may contain only a subset of views! (no all views are contained in the reconstruction)
# Matching entries are determined by view['key'] == extrinsics['key']
cams = []
# Mapping from input images to reconstructed cameras
image_index_to_camera_index = {}
# IMPORTANT: Views contains number of input images
# (this may be more than the number of reconstructed poses)
for rec_index, extrinsic in enumerate(extrinsics): # Iterate over extrinsics, not views!
camera = Camera()
# The key is defined w.r.t. view indices (NOT reconstructed camera indices)
view_index = int(extrinsic['key'])
image_index_to_camera_index[view_index] = rec_index
view = views[view_index]
camera.file_name = view['value']['ptr_wrapper']['data']['filename']
id_intrinsic = view['value']['ptr_wrapper']['data']['id_intrinsic']
# handle intrinsic params
intrinsic_params = intrinsics[int(id_intrinsic)]['value']['ptr_wrapper']['data']
focal_length = intrinsic_params['focal_length']
principal_point = intrinsic_params['principal_point']
if 'disto_k3' in intrinsic_params:
logger.info('3 Radial Distortion Parameters are not supported')
assert False
# For Radial there are several options: "None", disto_k1, disto_k3
if 'disto_k1' in intrinsic_params:
radial_distortion = float(intrinsic_params['disto_k1'][0])
else: # No radial distortion, i.e. pinhole camera model
radial_distortion = 0
camera.set_calibration(
np.asarray([[focal_length, 0, principal_point[0]],
[0, focal_length, principal_point[1]],
[0, 0, 1]], dtype=float),
radial_distortion
)
# handle extrinsic params (pose = extrinsic)
extrinsic_params = extrinsic['value']
cam_rotation_list = extrinsic_params['rotation']
camera.set_rotation_mat(np.array(cam_rotation_list, dtype=float))
camera._center = np.array(extrinsic_params['center'], dtype=float).T
# the camera looks in the z direction
cam_view_vec_cam_coordinates = np.array([0, 0, 1]).T
# transform view direction from cam coordinates to world coordinates
# for rotations the inverse is equal to the transpose
rotation_inv_mat = camera.get_rotation_mat().T
camera.normal = rotation_inv_mat.dot(cam_view_vec_cam_coordinates)
camera.view_index = view_index
cams.append(camera)
return cams, image_index_to_camera_index