move scipy to test dependencies + remove some usage (mirror #754)

[pengzhenghao]

What changes do you make in this PR?

• Please describe why you create this PR

resolve #754

Checklist

• I have merged the latest main branch into current branch.
• I have run bash scripts/format.sh before merging.
• Please use "squash and merge" mode.

[pengzhenghao]

@DhlinV @QuanyiLi
Seems like the point_cloud_lidar depends on the scipy to do fast rotation. But I don't find clear call to the get_rgb_array_cpu from anywhere.

Is it safe to remove scipy dependency?

[DhlinV]

@pengzhenghao I think it's safe since the rotation is used only after the parent class depth computes the depth value. Moving it inside the function shouldn't affect functionality. However, I'm not sure whether it would introduce additional overhead for point cloud-based training.

Finally, I implemented a NumPy version, and it runs without issues on my Linux system. The efficiency doesn't seem to be significantly impacted either, but it might need your double-check. Thanks!

rotation function:

def euler_to_rotation_matrix(hpr):
    """
    Convert ZYX Euler angles to a rotation matrix.
    
    Parameters:
        hpr (array-like): [yaw (Z), pitch (Y), roll (X)] in degrees.
    
    Returns:
        numpy.ndarray: 3x3 rotation matrix.
    """
    hpr = np.radians(hpr)
    
    cz, sz = np.cos(hpr[0]), np.sin(hpr[0])  # Yaw (Z)
    cy, sy = np.cos(hpr[1]), np.sin(hpr[1])  # Pitch (Y)
    cx, sx = np.cos(hpr[2]), np.sin(hpr[2])  # Roll (X)

    rotation_matrix = np.array([
        [cz * cy, cz * sy * sx - sz * cx, cz * sy * cx + sz * sx],
        [sz * cy, sz * sy * sx + cz * cx, sz * sy * cx - cz * sx],
        [-sy,     cy * sx,                cy * cx]
    ])

    return rotation_matrix

replace

from scipy.spatial.transform import Rotation as R
rot = R.from_euler('ZYX', hpr, degrees=True)

rotation_matrix = rot.as_matrix()

by

rotation_matrix = euler_to_rotation_matrix(hpr)

[pengzhenghao]

Cool could you make a commit?

[pengzhenghao]

Actually I don't know who've ever called this function. Do we have unit test / profile for this function?

[DhlinV]

@pengzhenghao Sorry for the delay, I just committed a pull request. And I think this function is called when running "metadrive/examples/point_cloud_lidar.py" (like a test script)