ORB (Oriented FAST and Rotated BRIEF) MCQ
FAST detector, intensity centroid orientation, steered BRIEF pairs, and fast Hamming matching for real-time apps.
FAST
Corner test
Orientation
Intensity centroid
rBRIEF
256 bits
Hamming
XOR popcount
ORB features
ORB combines FAST corners, a simple orientation from intensity moments, and rotation-aware BRIEF bit patterns—optimized for speed on CPUs and embedded devices.
Why binary?
Popcount Hamming distance is extremely fast; storage is compact—tradeoff vs SIFT discrimination.
Pieces
FAST
Compare circle of pixels to center with contiguous arc test—very fast corner detector.
Steered BRIEF
Rotate sampling pattern using θ so bits are rotation invariant.
Learning pairs
ORB selects BRIEF point pairs with lower correlation for better discrimination.
vs SIFT
ORB is faster and free; SIFT often stronger under hard illumination/viewpoint.
Matching cost
Hamming distance between 256-bit strings