Explain the method of overlapping and intersecting, Data Structure & Algorithms

Assignment Help:

Overlapping or Intersecting

A polygon overlaps or intersects the current background if any of its sides cuts the edges of the viewport as depicted at the top right corner of the viewport.

The extent of a polygon overlapping the viewport is only a necessary but not sufficient condition, because even if the extent overlaps, the polygon may be disjoint, as illustrated at the top left corner of the viewport. It may be seen that only the surrounding and contained cases (a) and (b) may be decided on the basis of the simple rules of relationship between the x-y extents of the polygon and the viewport. All other cases need further investigation, as follows : 

We start with the entire viewport, and examine all the polygons for surrounding or containment. Whatever polygons can be classified as Case (a) or Case (b) can be stored or not depending on whether they are visible or not.

For any remaining polygons, the viewport is divided into four quarters, and each quarter representing a viewport segment is evaluated against the polygon portions in that quarter for cases (a) and (b). The quarter or quarters in which such determination cannot be made will again be subdivided into four further quarters each, and each quarter (which may be termed a "viewport segment") examined for the same kind of relationship decisions.

This procedure is applied with successive subdivisions until all the polygons and sub-regions can be resolved as (a) or (b). Frequently, the procedure may have to be repeated until the last quartering reduces to a single pixel. Because of the four branches formed with each quartering step, the method is also called the Quad tree method. Finally, the method illustrates the difference between hidden-line and hidden-surface algorithms. In a particular viewport segment, it may happen that there are no edges at all, but two or more surfaces are surrounding the viewport segment. Here, hidden line has no relevance, but hidden surface has. 

 


Related Discussions:- Explain the method of overlapping and intersecting

Data mining assignment, The assignment aims at consolidating your knowledge...

The assignment aims at consolidating your knowledge on data mining techniques and developing practical skills through solving a problem of transcription factor binding sites recogn

Deletion of an element from the linear array, Program will demonstrate dele...

Program will demonstrate deletion of an element from the linear array /* declaration of delete_list function */ voiddelete_list(list *, int); /* definition of delete_list

Find the optimal solution - branch and bound algorithm, Consider the follow...

Consider the following 5-city traveling salesman problem. The distance between each city (in miles) is shown in the following table: (a) Formulate an IP whose solution will

Explain the abstract data type assertions, Explain the Abstract data type a...

Explain the Abstract data type assertions Generally, ADT assertions translate into assertions about the data types which implement ADTs, which helps insure that our ADT impleme

What is a height balanced tree, What is a height balanced tree? Height Ba...

What is a height balanced tree? Height Balanced Tree (AVL Tree) An AVL tree is a binary search tree in which the height of the left and right subtree of the root vary by at most

Splaying procedure, For splaying, three trees are maintained, the central, ...

For splaying, three trees are maintained, the central, left & right sub trees. At first, the central subtree is the complete tree and left and right subtrees are empty. The target

Algorithm, what algorithms can i use for the above title in my project desi...

what algorithms can i use for the above title in my project desing and implmentation of road transport booking system

Stack, using a program flowchart design a program to illustrate pop and pus...

using a program flowchart design a program to illustrate pop and push operation

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd