Cohen-Sutherland Line Clipping Algorithm

Pseudo Code of the Algorithm

Input: Two Endpoints of the line, ((x_0, y_0)) & ((x_1, y_1)).
Two opposite corner points of the frame buffer.

Steps of the Algorithm

1. Initialize Endpoints:
   Set (P_0 = (x_0, y_0)) and (P_1 = (x_1, y_1)).

2. Compute 4-bit Codes:
   Compute the 4-bit codes for each endpoint based on their relative position to the clipping window. The codes are determined as follows:

Source: From Academic Tutorials

The code "0000" represents the clip window, and all other areas outside are to be clipped.

• If both codes are "0000" (bitwise OR of the codes yields "0000"), the line lies completely inside the window. Pass the endpoints to the draw routine.
• If both codes have a "1" in the same bit position (bitwise AND of the codes is not "0000"), the line lies outside the window and can be trivially rejected.

3. Clipping Decision:
   If a line cannot be trivially accepted or rejected, it implies that at least one of the two endpoints lies outside the window, and the line segment crosses a window edge. In such cases, the line must be clipped at the window edge before being passed to the drawing routine.

4. Examine Endpoint Codes:
   Examine one of the endpoints, say (P_0), and read (P_0)'s 4-bit code in order: Left-to-Right, Bottom-to-Top.

5. Clipping at Window Edge:
   When a set bit ("1") is found in the 4-bit code, compute the intersection (I) of the corresponding window edge with the line from (P_0) to (P_1). Replace (P_0) with (I) and repeat the algorithm.

This algorithm efficiently determines and clips line segments that extend beyond the specified window, ensuring that only the visible portion is considered for rendering.