Cohen-Sutherland Line Clipping Algorithm
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The document discusses the Cohen-Sutherland line clipping algorithm, which is used to efficiently find visible portions of a line that may extend beyond the edges of a screen. It categorizes line endpoints based on whether they fall inside or outside the clipping rectangle, utilizing specific conditions to accept or reject lines. The algorithm divides the 2D space into nine regions to determine the necessary clipping actions for different line configurations.
Cohen-Sutherland Line Clipping Algorithm
- 2. Group 3 Cohen-Sutherland Line Clipping Algorithm
- 3. Hosted By M.M. Arifin Ferdous Joy 131-15-2614 Md. Touhidul Hasan Shadi 132-15-2680 Maruf Abdullah (Rion) 132-15-2703
- 4. Introduction When drawing a 2D line on screen, it might happen that one or both of the endpoints are outside the screen while a part of the line should still be visible. In that case, an efficient algorithm is needed to find two new endpoints that are on the edges on the screen, so that the part of the line that's visible can now be drawn. This way, all those points of the line outside the screen are clipped away and you don't need to waste any execution time on them. A good clipping algorithm is the Cohen-Sutherland algorithm for this solution.
- 5. Here are a few cases, where the black rectangle represents the screen, in red are the old endpoints, and in blue the ones after clipping: Case A: Both end-points are inside the screen, so no clipping needed. CASE A
- 6. Case B: One end-point outside the screen, that one had to be clipped. Case C: both endpoint are outside the screen, and no part of the line is visible, don't draw it at all. Case D: both endpoint are outside the screen, and a part of the line is visible, clip both endpoints and draw it. CASE B CASE C CASE D
- 7. Cohen Sutherland Clipping Algorithm Now we will learn what is Cohen Sutherland Clipping Algorithm and how it works. This algorithm clips a line to the clipping rectangle. It concerns itself with performing the simple cases quickly.
- 8. In this algorithm it divides lines & edges into 2 cases. 1) Trivially Accept and 2) Trivially Reject.
- 9. Conditions of Trivially Accept Xmin ≤ X ≤ Xmax Ymin ≤ Y ≤ Ymax Lines fulfill this conditions then we will mark those lines as trivially accept. Ymax Ymin Xmin Xmax
- 10. Conditions of Trivially Reject X0 < Xmin & X1 < Xmin or Y0 < Ymin & Y1 < Ymin X0 > Xmax & X1 > Xmax or Y0 > Ymax & Y1 > Ymax
- 11. Question Arrives We must have a question now?? A B Then we will move forward for solve this ……..
- 12. The algorithm divides the 2D space in 9 regions: This is also known as ABRL CODE Figure: 2D space in 9 regions
- 13. The center region is the screen or Window Position (0000). If the region is above the screen, the first bit is 1. If the region is below the screen, the second bit is 1. If the region is to the right of the screen, the third bit is 1. If the region is to the left of the screen, the fourth bit is 1.
- 14. A (0100) B (0010) AND Operation Then get the new point C (0000)
- 15. C (0000) B (0010) AND Operation Then get the new point D (0000) Then we have the final line after clipping is CD
- 16. Handling Similar Situations If similar problems arrive then we have to clip those according to mentioned method. Some examples of similar situations
- 17. Any Questions??