Which of the following statements regarding Cohen-Sutherland algorithm is…
Which of the following statements regarding Cohen-Sutherland algorithm is INCORRECT?
Answer: B. In Visible clipping category, both endpoints of the line lie outside the window. — Answer: The incorrect statement is: "In Visible clipping category, both endpoints of the line lie outside the window." In the Cohen-Sutherland algorithm, a…
- A.
In Cohen-Sutherland algorithm, line clipping process is divided into two phases.
- B.
In Visible clipping category, both endpoints of the line lie outside the window.
- C.
In Cohen-Sutherland algorithm, the plane is divided into nine regions.
- D.
In Cohen-Sutherland algorithm, the third clipping category is called Clipping Candidate.
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Correct answer: B
Answer: The incorrect statement is: "In Visible clipping category, both endpoints of the line lie outside the window."
In the Cohen-Sutherland algorithm, a region code of 0000 for a point means that the point is inside the clipping window.
If both points P and Q have codes 0000, it means both lie inside the clipping window.
Therefore, the entire line segment joining P and Q is totally inside the clipping window and is trivially accepted.
Cohen–Sutherland classification:
Visible (trivially accepted): both endpoints are inside the window (region code 0000).
Invisible (trivially rejected): both endpoints lie outside the window in such a way that their region codes share a common 1 bit (bitwise AND of codes ≠ 0).
Clipping candidate: the line is neither trivially accepted nor trivially rejected and must be clipped (compute intersections and update region codes).
Other key facts:
The plane is divided into nine regions: the central inside region and eight outside regions (top, bottom, left, right, and four corners).
The algorithm proceeds in two phases: a trivial acceptance/rejection test using region codes, followed by an iterative clipping phase that computes line intersections with window boundaries until the line is accepted or rejected.
Conclusion: The statement claiming both endpoints lie outside in the visible category is incorrect; visible means both endpoints are inside the window (region code 0000).