# Computer Graphics Questions & Answers – Other Polygon Clipping Algorithms

This set of Computer Graphics Multiple Choice Questions & Answers (MCQs) focuses on “Other Polygon Clipping Algorithms”.

1. How many types of basic polygons are present?
a) 4
b) 2
c) 10
d) 5

Explanation: There are two types of basic polygons present. They are concave polygons and convex polygons. In a concave polygon at least one angle should be greater than 180. In a convex polygon all the angles should be less than 180.

2. A polygon can be a figure whose all edges are not connected with another edge.
a) True
b) False

Explanation: In a polygon, all lines are connected. Lines can be a combination of edges and vertices, which together form a polygon. It is a 2-dimensional shape made by connecting multiple straight lines.

3. Which of the following part of a polygon is considered in a polygon clipping algorithm?
a) Part which is both inside and outside the window
b) Part which is outside the window
c) Part which is inside the window
d) Part which is neither inside nor outside the window

Explanation: Polygon clipping is a process in which we only consider the part which is inside the view pane or window. We will remove or clip the part that is outside the window.

4. Which of the following polygon clipping algorithm can be used to clip a filled area?
a) Sutherland Hodgman Clipping Algorithm
b) Weiler Atherton Clipping Algorithm
c) Vatti Clipping Algorithm
d) Greiner Hormann Clipping Algorithm

Explanation: Weiler Atherton Clipping algorithm helps us to clip a filled area. The filled area may be a convex polygon or concave polygon. This algorithm was introduced to identify the visible surfaces. This algorithm helps to create individual polygons in some cases.

5. In Weiler Atherton Clipping Algorithm which of the following is consider to clip a polygon?
a) Polygon edges and Window boundaries
b) Polygon Vertices
c) Polygon Edges
d) Window boundaries

Explanation: In the Weiler Atherton algorithm, we consider the view pane boundaries instead of edges and vertices of the polygon to clip a polygon. Points very close to the edge of the other polygon may be considered as both in and out until their status can be confirmed after all the intersections have been found and verified but this increases the complexity.

6. Which of the following algorithm can be used to clip a self-intersecting polygon?
a) Greiner Hormann Clipping Algorithm
b) Weiler Atherton Clipping Algorithm
c) Vatti Clipping Algorithm
d) Both Vatti and Greiner Hormann Clipping Algorithm

Explanation: To clip a self-intersecting polygon we can use the Vatti Clipping Algorithm as well as the Greiner Hormann Clipping Algorithm. Polygons with holes can also be clipped using these algorithms. Algorithms like Sutherland-Hodgman and Weiler-Atherton cannot perform clipping on a self-intersecting polygon.

7. Vatti Clipping Algorithm uses the sweep line approach to clip a polygon.
a) True
b) False

Explanation: The Vatti Clipping algorithm uses the sweep line approach to clip a polygon. In scan line approach the selected polygon is selected and placed upon imaginary horizontal lines that passes through the polygons every vertex and divides the polygon on different parts.

8. Greiner Hormann Clipping Algorithm is more efficient than the Vatti Clipping Algorithm.
a) True
b) False

Explanation: The Greiner Hormann Clipping Algorithm works better than the Vatti Clipping Algorithm. It can work on self-intersecting polygons as well as non-convex polygons but it cannot work upon polygons having common edges.

9. Which of the following algorithm can be used to clip a polygon in 3D space?
a) Weiler Atherton Algorithm
b) Vatti Clipping Algorithm
c) Greiner Hormann Clipping Algorithm
d) Polygon in 3D space cannot be clipped

Explanation: The algorithm that can be used in 3D space as well is Weiler Atherton Algorithm. It is mostly used in 2D space but can be used in 3D space with the help of Z-ordering. The Vatti Clipping algorithm and Greiner Hormann Clipping algorithm only works on 2D space.

10. Which of the following clipping algorithm is based upon the “inside” of a polygon based on the winding number?
a) Sutherland Hodgman Clipping Algorithm
b) Weiler Atherton Clipping Algorithm
c) Vatti Clipping Algorithm
d) Greiner Hormann Clipping Algorithm

Explanation: The Greiner Hormann Clipping algorithm is based upon the “inside” of a polygon based on the winding number. The winding number of a closed curve in the plane around a given point is an integer representing the total number of times that curve travels counter clockwise around the point. The algorithm considers regions with odd winding number to be inside the polygon.

Sanfoundry Global Education & Learning Series – Computer Graphics.

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