symforce.cam.double_sphere_camera_cal module

class DoubleSphereCameraCal(focal_length, principal_point, xi, alpha)[source]

Bases: CameraCal

Camera model where a point is consecutively projected onto two unit spheres with centers shifted by xi, then projected into the image plane using the pinhole model shifted by alpha / (1 - alpha).

There are important differences here from the derivation in the paper and in other open-source packages with double sphere models; see notebooks/double_sphere_derivation.ipynb for more information.

The storage for this class is:

[ fx fy cx cy xi alpha ]

TODO(aaron): Create double_sphere_derivation.ipynb

TODO(aaron): Probably want to check that values and derivatives are correct (or at least sane) on the valid side of the is_valid boundary

Reference:

https://vision.in.tum.de/research/vslam/double-sphere

Parameters:

  • focal_length (T.Sequence[T.Scalar]) –

  • principal_point (T.Sequence[T.Scalar]) –

  • xi (T.Scalar) –

  • alpha (T.Scalar) –

NUM_DISTORTION_COEFFS = 2
classmethod symbolic(name, **kwargs)[source]

Construct a symbolic element with the given name prefix. Kwargs are forwarded to sf.Symbol (for example, sympy assumptions).

Parameters:

  • name (str) –

  • kwargs (Any) –

Return type:

DoubleSphereCameraCal

property xi: float
property alpha: float
classmethod storage_order()[source]

Return list of the names of values returned in the storage paired with the dimension of each value.

Return type:

Tuple[Tuple[str, int], …]

pixel_from_camera_point(point, epsilon=0.0)[source]

Project a 3D point in the camera frame into 2D pixel coordinates.

Returns:

  • pixel – (x, y) coordinate in pixels if valid

  • is_valid – 1 if the operation is within bounds else 0

Parameters:
Return type:

Tuple[Matrix21, float]

camera_ray_from_pixel(pixel, epsilon=0.0)[source]

Backproject a 2D pixel coordinate into a 3D ray in the camera frame.

Returns:

  • camera_ray – The ray in the camera frame (NOT normalized)

  • is_valid – 1 if the operation is within bounds else 0

Parameters:
Return type:

Tuple[Matrix31, float]