Search results
Results from the WOW.Com Content Network
Clipping, in the context of computer graphics, is a method to selectively enable or disable rendering operations within a defined region of interest. Mathematically, clipping can be described using the terminology of constructive geometry .
The outcode will have 4 bits for two-dimensional clipping, or 6 bits in the three-dimensional case. The first bit is set to 1 if the point is above the viewport. The bits in the 2D outcode represent: top, bottom, right, left. For example, the outcode 1010 represents a point that is top-right of the viewport.
The Nicholl–Lee–Nicholl algorithm is a fast line-clipping algorithm that reduces the chances of clipping a single line segment multiple times, as may happen in the Cohen–Sutherland algorithm. The clipping window is divided into a number of different areas, depending on the position of the initial point of the line to be clipped.
Note that a point is defined as being inside an edge if it lies on the same side of the edge as the remainder of the polygon. If the vertices of the clip polygon are consistently listed in a counter-clockwise direction, then this is equivalent to testing whether the point lies to the left of the line (left means inside , while right means ...
Cyrus–Beck is a general algorithm and can be used with a convex polygon clipping window, unlike Cohen-Sutherland, which can be used only on a rectangular clipping area. Here the parametric equation of a line in the view plane is p ( t ) = t p 1 + ( 1 − t ) p 0 {\displaystyle \mathbf {p} (t)=t\mathbf {p} _{1}+(1-t)\mathbf {p} _{0}} where 0 ...
The value of the line function at this midpoint is the sole determinant of which point should be chosen. The adjacent image shows the blue point (2,2) chosen to be on the line with two candidate points in green (3,2) and (3,3). The black point (3, 2.5) is the midpoint between the two candidate points.
Clipping is an operation that limits rasterisation to a limited, usually rectangular, area. This is done by moving the start- and end points of the given line to the borders of this area if they lie outside of it. Generally, this leads to the coordinates of these points no longer being integer numbers.
Using the Nicholl–Lee–Nicholl algorithm, the area around the clipping window is divided into a number of different areas, depending on the position of the initial point of the line to be clipped. This initial point should be in three predetermined areas; thus the line may have to be translated and/or rotated to bring it into the desired region.