Module camera

Classes and functions for simulating cameras.

Simple vs Calibrated Camera

There are two different camera implementations: Camera and CalibratedCamera.

Camera first one only takes the camera’s position, orientation and field of view as input and uses PyBullet functions to compute the corresponding transformation/projection from it.

CalibratedCamera expects a full camera matrix and distortion coefficients (like they are acquired through camera calibration. By using the calibration parameters of a real camera here, the rendered images are much closer to the real ones. On the downside the rendering process is a bit slower as applying the distortion takes some time.

Loading calibration parameters from a single YAML file can be done using CameraParameters.load(). To load the calibration parameters of all three cameras of a TriFinger platform, load_camera_parameters() can be used.

Camera Arrays

CameraArray provides a simple interface to get images from an arbitrary number of cameras.

When specifically simulating the three-camera-setup of the TriFinger platform, you can use TriFingerCameras for the simple camera model or create_trifinger_camera_array_from_config() for the model using the full calibration parameters.

class trifinger_simulation.camera.CalibratedCamera(camera_matrix, distortion_coefficients, tf_world_to_camera, image_size, near_plane_distance, far_plane_distance, pybullet_client_id=0)

Simulate a camera based on calibration parameters.

This class renders images from the simulation, using calibration parameters from a real camera. It uses a more accurate projection matrix as Camera and also takes distortion into account.

Parameters:

• camera_matrix –

  Camera matrix containing focal length and centre point:

  \[\begin{split}\begin{bmatrix} f_x & 0 & c_x \\ 0 & f_y & c_y \\ 0 & 0 & 0 \end{bmatrix}\end{split}\]

• distortion_coefficients – Distortion coefficients (k_1, k_2, p_1, p_2, k_3)

• tf_world_to_camera – Homogeneous transformation matrix from world to camera frame.

• image_size – Size of the image given as (width, height).

• near_plane_distance – Minimum distance to camera for objects to be rendered. Objects that are closer to the camera are clipped.

• far_plane_distance – Maximum distance to the camera for objects to be rendered. Objects that are further away are clipped.

• pybullet_client_id – Id of the pybullet client (needed when multiple clients are running in parallel).

distort_image(image)

Distort an image based on the cameras distortion coefficients.

Parameters:

image – The undistorted image.

Returns:

The distorted image.

get_height()

Get height of the images rendered by this camera instance.

Return type:

int

get_image(renderer=131072)

Get a rendered and distorted image from the camera.

Parameters:

renderer – Specify which renderer is to be used. The renderer used by default relies on X server. Note: this would need visualization to have access to OpenGL. In order to use the renderer without visualization, as in, in the “DIRECT” mode of connection, use the ER_TINY_RENDERER.

Returns:

Rendered RGB image from the simulated camera.

Return type:

array, shape=(height, width, 3)

get_width()

Get width of the images rendered by this camera instance.

Return type:

int

class trifinger_simulation.camera.Camera(camera_position, camera_orientation, image_size=(270, 270), field_of_view=52, near_plane_distance=0.001, far_plane_distance=100.0, pybullet_client_id=0)

Represents a camera in the simulation environment.

Note: This class uses a simplified camera model. For images that better match with the real cameras, use CalibratedCamera.

Parameters:

• camera_position – Position (x, y, z) of the camera w.r.t. the world frame.

• camera_orientation – Quaternion (x, y, z, w) representing the orientation of the camera.

• image_size – Tuple (width, height) specifying the size of the image.

• field_of_view – Field of view of the camera

• near_plane_distance – see OpenGL’s documentation for details

• far_plane_distance – see OpenGL’s documentation for details

• target_position – where should the camera be pointed at

• camera_up_vector – the up axis of the camera

• pybullet_client_id – Id of the pybullet client (needed when multiple clients are running in parallel).

get_height()

Get height of the images rendered by this camera instance.

Return type:

int

get_image(renderer=131072)

Get a rendered image from the camera.

Parameters:

renderer – Specify which renderer is to be used. The renderer used by default relies on X server. Note: this would need visualization to have access to OpenGL. In order to use the renderer without visualization, as in, in the “DIRECT” mode of connection, use the ER_TINY_RENDERER.

Returns:

Rendered RGB image from the simulated camera.

Return type:

array, shape=(height, width, 3)

get_width()

Get width of the images rendered by this camera instance.

Return type:

int

class trifinger_simulation.camera.CameraArray(cameras)

Array of an arbitrary number of cameras.

Parameters:

cameras (Sequence[BaseCamera]) – List of cameras.

get_bayer_images(renderer=131072)

Get Bayer images.

Same as get_images() but returning the images as BG-Bayer patterns instead of RGB.

Return type:

List[ndarray]

get_images(renderer=131072)

Get images.

See Camera.get_image() for details.

Returns:

List of RGB images, one per camera.

Return type:

List[ndarray]

class trifinger_simulation.camera.CameraParameters(name, width, height, camera_matrix, distortion_coefficients, tf_world_to_camera)

Represents intrinsic and extrinsic parameters of a camera.

See description of properties for the meaning of the constructor arguments.

Create new instance of CameraParameters(name, width, height, camera_matrix, distortion_coefficients, tf_world_to_camera)

Parameters:

• name (str)

• width (int)

• height (int)

• camera_matrix (ndarray)

• distortion_coefficients (ndarray)

• tf_world_to_camera (ndarray)

dump(stream)

Dump camera parameters in YAML format to the given output stream.

Parameters:

stream (TextIO) – Output stream.

classmethod load(stream)

Load camera parameters from a YAML stream.

Parameters:

stream (TextIO) – Input stream of configuration in YAML format.

Returns:

Instance of CameraParameters with values set based on the input YAML.

Return type:

CameraParameters

camera_matrix: ndarray

Camera projection matrix. Shape = (3, 3)

distortion_coefficients: ndarray

Distortion coefficients. Shape = (5,)

height: int

Height of the images.

name: str

Name of the camera.

tf_world_to_camera: ndarray

Transformation matrix from world to camera frame. Shape = (4, 4)

width: int

Width of the images.

class trifinger_simulation.camera.TriFingerCameras(**kwargs)

Simulate the three cameras of the TriFinger platform.

Note

This uses the simple camera model (see Camera). To get images that are more closely matching those of the real cameras use create_trifinger_camera_array_from_config() instead.

Parameters:

cameras – List of cameras.

trifinger_simulation.camera.calib_data_to_matrix(data)

Extract a matrix from a camera parameter dict (as loaded from YAML).

Parameters:

data (dict)

Return type:

ndarray

trifinger_simulation.camera.create_trifinger_camera_array(camera_parameters, pybullet_client_id=0)

Create a TriFinger camera array using camera calibration parameters.

Parameters:

• camera_parameters (Iterable[CameraParameters]) – List of camera calibration parameters for the three cameras.

• pybullet_client_id – Id of the pybullet client (needed when multiple clients are running in parallel).

Returns:

CameraArray with three cameras.

Return type:

CameraArray

trifinger_simulation.camera.create_trifinger_camera_array_from_config(config_dir, calib_filename_pattern='camera{id}.yml', pybullet_client_id=0)

Create a TriFinger camera array using camera calibration files.

Loads camera calibration files from the given directory and uses them to create a CameraArray of CalibratedCamera.

Parameters:

• config_dir (Path) – Directory containing the camera calibration files.

• calib_filename_pattern – Template for the camera calibration file names. ‘{id}’ will be replaced with the camera id (60, 180, 300).

• pybullet_client_id – Id of the pybullet client (needed when multiple clients are running in parallel).

Returns:

CameraArray with three cameras.

Return type:

CameraArray

trifinger_simulation.camera.rbg_to_bayer_bg(image)

Convert an rgb image to a BG Bayer pattern.

This can be used to generate simulated raw camera data in Bayer format. Note that there will be some loss in image quality. It is mostly meant for testing the full software pipeline with the same conditions as on the real robot. It is not optimized of realistic images.

Parameters:

image (ndarray) – RGB image.

Returns:

Bayer pattern based on the input image. Height and width are the same as of the input image. The image can be converted using OpenCV’s COLOR_BAYER_BG2*.

Return type:

ndarray