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Clipping is defined as the interaction of subject and clip polygons. While clipping usually involves finding the intersections (regions of overlap) of subject and clip polygons, clipping algorithms can also be applied with other boolean clipping operations: difference, where the clipping polygons remove overlapping regions from the subject; union, where clipping returns the regions covered by ...
Vector overlay is an operation (or class of operations) in a geographic information system (GIS) for integrating two or more vector spatial data sets. Terms such as polygon overlay, map overlay, and topological overlay are often used synonymously, although they are not identical in the range of operations they include.
The Weiler–Atherton is a polygon-clipping algorithm. It is used in areas like computer graphics and games development where clipping of polygons is needed. It allows clipping of a subject or candidate polygon by an arbitrarily shaped clipping polygon/area/region. It is generally applicable only in 2D.
Once all sides of the clip polygon have been processed, the final generated list of vertices defines a new single polygon that is entirely visible. Note that if the subject polygon was concave at vertices outside the clipping polygon, the new polygon may have coincident (i.e., overlapping) edges – this is acceptable for rendering, but not for ...
In addition, many systems have tracing tools, so that newly digitized lines can exactly follow existing lines. During the overlay process, the preferred mode of sliver polygon prevention is the use of a fuzzy tolerance, which is sometimes called a "xy tolerance" (ArcGIS) or "snapping threshold" (GRASS), and was originally called an "epsilon ...
Some GIS software has tools for validating topological integrity rules (e.g. not allowing polygons to overlap or have gaps) on spaghetti data to prevent and/or correct topological errors. A hybrid topological data model has the option of storing topological relationship information as a separate layer built on top of a spaghetti data set.
A fractal landscape being rendered using the painter's algorithm on an Amiga. The painter's algorithm (also depth-sort algorithm and priority fill) is an algorithm for visible surface determination in 3D computer graphics that works on a polygon-by-polygon basis rather than a pixel-by-pixel, row by row, or area by area basis of other Hidden-Surface Removal algorithms.
Early algorithms for Boolean operations on polygons were based on the use of bitmaps.Using bitmaps in modeling polygon shapes has many drawbacks. One of the drawbacks is that the memory usage can be very large, since the resolution of polygons is proportional to the number of bits used to represent polygons.