fix: quaternion normalization divides by zero for anti-parallel

[andrewwhitecdw]

Problem

fix: quaternion normalization divides by zero for anti-parallel vectors

Fix

Replace:

def quat_between_vectors(u, v):
    """Return the quaternion transformation between two vectors."""
    xyz = np.cross(u, v)
    w = np.sqrt(np.linalg.norm(u)**2 * np.linalg.norm(v)**2) + np.dot(u, v)
    q = [xyz[0], xyz[1], xyz[2], w]
    return q / np.linalg.norm(q)

with:

def quat_between_vectors(u, v):
    """Return the quaternion transformation between two vectors."""
    xyz = np.cross(u, v)
    w = np.sqrt(np.linalg.norm(u)**2 * np.linalg.norm(v)**2) + np.dot(u, v)
    q = np.array([xyz[0], xyz[1], xyz[2], w])
    norm = np.linalg.norm(q)
    if norm < 1e-12:
        # Anti-parallel vectors: choose any axis perpendicular to u
        tmp = np.array([1.0, 0.0, 0.0]) if abs(u[0]) < abs(u[1]) else np.array([0.0, 1.0, 0.0])
        xyz = np.cross(u, tmp)
        q = np.array([xyz[0], xyz[1], xyz[2], 0.0])
        norm = np.linalg.norm(q)
    return q / norm

Files changed

• utils/uniform_sphere.py