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Simulo

simulo.SensorOffset

Offset configuration for sensor placement relative to parent frame.

Used to specify the position and orientation of a sensor relative to its attachment point (e.g., camera offset from robot base).

Attributes:

  • pos — Position offset (x, y, z) in meters
  • rot — Rotation as quaternion (w, x, y, z) - wxyz convention
  • convention — Coordinate frame convention (“opengl”, “ros”, “world”)

For cameras, hand-tuning rot quaternions is error-prone — identity rotation in ROS convention makes the camera stare straight up at the parent’s +Z axis, not forward. Prefer look_at() to derive the quaternion from a camera position and a target point.

simulo.SensorOffset(
    pos: Tuple[float, float, float] = (0.0, 0.0, 0.0),
    rot: Tuple[float, float, float, float] = (1.0, 0.0, 0.0, 0.0),
    convention: str = 'opengl',
)

look_at()

Section titled “look_at()”
SensorOffset.look_at(
    pos: Tuple[float, float, float],
    target: Tuple[float, float, float] = (0.0, 0.0, 0.0),
    up_hint: Tuple[float, float, float] = (0.0, 0.0, 1.0),
    convention: str = 'ros',
) -> SensorOffset

classmethod

Return a SensorOffset whose camera looks at target from pos.

Computes a ROS-optical-frame quaternion so the camera’s +Z axis (forward) points from pos toward target and the camera’s +Y axis (down in image) is perpendicular to up_hint. The degenerate case (forward parallel to up_hint — i.e., camera looking straight up or down along the parent’s Z axis) returns the canonical (0, 1, 0, 0) “look down” quaternion when looking down, identity “look up” when looking up.

Args:

  • pos — Camera position in the parent (attachment) frame.
  • target — Point the camera should point at, in the parent frame. Defaults to the parent’s origin.
  • up_hint — World-space “up” direction. Defaults to (0, 0, 1).
  • convention — Frame convention passed through to the returned SensorOffset. Defaults to “ros” since look-at math is expressed in ROS optical-frame convention.

Examples: Top-down camera 4m above the torso looking straight down:

offset = SensorOffset.look_at(pos=(0, 0, 4))

Side camera 3m to the right + 2m up, looking back at the robot:

offset = SensorOffset.look_at(pos=(3, 0, 2))

Over-the-shoulder camera 2m behind + 1.5m up:

offset = SensorOffset.look_at(pos=(-2, 0, 1.5))