In this video we will learn scan line polygon fill algorithm in computer graphics.
We will learn the basic concept of scan line polygon fill algorithm.
We will also take a look at an example of scan line polygon fill algorithm,
Scan line polygon filling algorithm is used for solid color filling in polygons.
Steps to perform:
For Scan line polygon filling there are three steps to perform in the following order:
Find the intersections of the scan line with all edges of the polygon.
Sort the intersections by increasing x-coordinate i.e. from left to right.
Make pairs of the intersections and fill in color within all the pixels inside the pair.
Special Cases:
Some scan-line intersections at polygon vertices require special handling.
A scan line passing through a vertex intersects two polygon edges at that position, adding two points to the list of intersections for the scan line.
In this example Scan line y and Scan line y` both pass through an vertex or an edge endpoint.
Now in case of scan line y` the scan line is intersecting 4 edges i.e. even number of edges and
Also passing through a vertex/endpoint.
ALSO both the edges that are connected to the vertex are on SAME SIDE, of the scan line.
SO we need to count the vertex/endpoint TWICE so that we can make pairs of intersection points (8,12) & (12,14).
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