Explain Polygon Fill algorithm

Polygon Fill algorithm is used in computer graphics to fill the area of the polygon. Here are the steps involved in the Polygon Fill algorithm:

1. Edge Table Creation: The first step in the polygon fill algorithm is to create an edge table (ET). This table contains a list of all the edges of the polygon sorted by the smallest y coordinate of the edge. Each entry in the table contains the smallest y coordinate of the edge, the largest y coordinate, the x coordinate corresponding to the smallest y coordinate, and the slope inverse of the edge.

2. Active Edge Table: The Active Edge Table (AET) is initially empty. It is filled with the edges when their smallest y coordinate becomes equal to the scan line. The edges are removed when the scan line is equal to the maximum y coordinate of the edge.

3. Filling: The scan line is initially at the minimum y coordinate. It is incremented by 1 unit until it reaches the maximum y coordinate. When the scan line is at a particular y coordinate, the edges whose minimum y coordinate is equal to the scan line are moved from the ET to the AET. The x coordinates in the AET are sorted in increasing order. Then, the pixels between pairs of x coordinates in the AET are filled.

4. Updating the AET: After filling the pixels on the current scan line, the AET is updated for the next scan line. The x coordinate for each edge is updated by adding the slope inverse to it. If the scan line becomes equal to the maximum y coordinate of an edge, that edge is removed from the AET.

5. Repeat Steps 3 and 4: Steps 3 and 4 are repeated until the scan line reaches the maximum y coordinate.

This algorithm is efficient because it only considers the pixels inside the polygon, and it can be used to fill polygons with any number of sides.