5. What is polygon clipping? Explain Sutherland Hodgman algorithm for polygon clipping.

Polygon clipping is a process used in computer graphics to remove certain parts of a polygon by a rectangular clipping window. It is used to only draw the parts of the polygon that will be visible in the final scene, which can improve performance by reducing the amount of drawing needed.

The Sutherland-Hodgman algorithm is a popular method for polygon clipping. Here's a step-by-step explanation of how it works:

1. Input: The algorithm takes two inputs - a subject polygon and a clip polygon. The subject polygon is the one that we want to clip, and the clip polygon is the shape that we use to clip the subject polygon.

2. Initialization: The algorithm starts with an empty list of output vertices.

3. Processing Each Edge of the Clip Polygon: The algorithm processes each edge of the clip polygon one by one. For each edge, it processes all vertices of the subject polygon.

4. Determining Whether to Keep or Discard Each Vertex: For each vertex of the subject polygon, the algorithm determines whether to keep it or discard it based on its position relative to the clip edge. If the vertex is on the inside of the clip edge, it is kept; otherwise, it is discarded.

5. Handling Intersections: If a vertex is on the outside of the clip edge, but the next vertex is on the inside, the algorithm calculates the intersection point of the edge connecting the two vertices and the clip edge, and adds this intersection point to the output list.

6. Updating the Subject Polygon: After processing all vertices for the current clip edge, the algorithm updates the subject polygon to be the list of output vertices, and clears the output list for the next clip edge.

7. Repeating the Process: The algorithm repeats steps 3-6 for each edge of the clip polygon.

8. Output: After all edges of the clip polygon have been processed, the remaining vertices form the clipped polygon.

This algorithm is efficient and can handle complex polygon shapes, but it only works for convex clip polygons. For non-convex clip polygons, other algorithms such as the Weiler-Atherton algorithm can be used.