def box_nuscenes_to_kitti(box: Box, velo_to_cam_rot: Quaternion,
velo_to_cam_trans: np.ndarray,
r0_rect: Quaternion,
kitti_to_nu_lidar_inv: Quaternion = Quaternion(axis=(0, 0, 1), angle=np.pi / 2).inverse) \
-> Box:
"""
Transform from nuScenes lidar frame to KITTI reference frame.
:param box: Instance in nuScenes lidar frame.
:param velo_to_cam_rot: Quaternion to rotate from lidar to camera frame.
:param velo_to_cam_trans: <np.float: 3>. Translate from lidar to camera frame.
:param r0_rect: Quaternion to rectify camera frame.
:param kitti_to_nu_lidar_inv: Quaternion to rotate nuScenes to KITTI LIDAR.
:return: Box instance in KITTI reference frame.
"""
# Copy box to avoid side-effects.
box = box.copy()
# Rotate to KITTI lidar.
box.rotate(kitti_to_nu_lidar_inv)
# Transform to KITTI camera.
box.rotate(velo_to_cam_rot)
box.translate(velo_to_cam_trans)
# Rotate to KITTI rectified camera.
box.rotate(r0_rect)
# KITTI defines the box center as the bottom center of the object.
# We use the true center, so we need to adjust half height in y direction.
box.translate(np.array([0, box.wlh[2] / 2, 0]))
return box
def project_kitti_box_to_image(
box: Box, p_left: np.ndarray,
imsize: Tuple[int, int]) -> Tuple[int, int, int, int]:
"""
Projects 3D box into KITTI image FOV.
:param box: 3D box in KITTI reference frame.
:param p_left: <np.float: 3, 4>. Projection matrix.
:param imsize: (width , height). Image size.
:return: (xmin, ymin, xmax, ymax). Bounding box in image plane.
"""
# Create a new box.
box = box.copy()
# KITTI defines the box center as the bottom center of the object.
# We use the true center, so we need to adjust half height in negative y direction.
box.translate(np.array([0, -box.wlh[2] / 2, 0]))
# Project corners to 2d to get bbox in pixel coords.
corners = np.array(
[corner for corner in box.corners().T if corner[2] > 0]).T
imcorners = view_points(corners, p_left, normalize=True)[:2]
bbox = (np.min(imcorners[0]), np.min(imcorners[1]),
np.max(imcorners[0]), np.max(imcorners[1]))
# Crop bbox to prevent it extending outside image
bbox_crop = (max(0, bbox[0]), max(0, bbox[1]), min(imsize[0], bbox[2]),
min(imsize[1], bbox[3]))
return bbox_crop
def project_kitti_box_to_image(box: Box, p_left: np.ndarray, imsize: Tuple[int, int]) \
-> Union[None, Tuple[int, int, int, int]]:
"""
Projects 3D box into KITTI image FOV.
:param box: 3D box in KITTI reference frame.
:param p_left: <np.float: 3, 4>. Projection matrix.
:param imsize: (width, height). Image size.
:return: (xmin, ymin, xmax, ymax). Bounding box in image plane or None if box is not in the image.
"""
# Create a new box.
box = box.copy()
# KITTI defines the box center as the bottom center of the object.
# We use the true center, so we need to adjust half height in negative y direction.
box.translate(np.array([0, -box.wlh[2] / 2, 0]))
# Check that some corners are inside the image.
corners = np.array(
[corner for corner in box.corners().T if corner[2] > 0]).T
if len(corners) == 0:
return None
# Project corners that are in front of the camera to 2d to get bbox in pixel coords.
imcorners = view_points(corners, p_left, normalize=True)[:2]
bbox = (np.min(imcorners[0]), np.min(imcorners[1]),
np.max(imcorners[0]), np.max(imcorners[1]))
# Crop bbox to prevent it extending outside image.
bbox_crop = tuple(max(0, b) for b in bbox)
bbox_crop = (min(imsize[0], bbox_crop[0]), min(imsize[0],
bbox_crop[1]),
min(imsize[0], bbox_crop[2]), min(imsize[1],
bbox_crop[3]))
# Detect if a cropped box is empty.
if bbox_crop[0] >= bbox_crop[2] or bbox_crop[1] >= bbox_crop[3]:
return None
return bbox_crop