Circular arc fast cutting method for rectangular window

Abstract

The invention discloses a method for quickly cutting an arc under a rectangular window. For any given arc section, according to occurrence probability and required operation of each type of arc, through an arc integral bounding box and a bounding box for each divided quadrant arc section in sequence, and through internal and external tests for a vertex of a cut window relative to the quadrant arcsection, the method uses less operation to exclude the arcs disjointed with the cut window as much as possible, and quickly obtain intersection of the arc and the edge of the cut window for the rest arcs demanding cross operation to finish cutting by looking up a table. The method has the advantage that the method only needs several times of displacements, integer addition-subtraction or little multiplication-division arithmetic for optional arc to be cut to quickly acquire cutting results thereof, and improves arc cutting efficiency greatly. Moreover, as arc cutting is the basis of graphics and CAD, the method can be widely applied to various drawing software, modeling software, CAD software, complex engineering drawing design systems and the like.

Description

technical field [0001] The invention relates to an arc cutting method, and in particular to a fast arc cutting method in a rectangular window. Background technique [0002] As one of the basic algorithms in computer graphics, the line clipping algorithm is directly related to the efficiency of the graphics system. In the aspect of rectangular window clipping of straight line segments, many classic algorithms have appeared, such as Cohen-Sutherland algorithm based on coding technology, Liang-Barsky algorithm based on parameterization method, Nicholl-Lee-Nicholl algorithm based on geometric transformation, and Nicholl-Lee-Nicholl algorithm based on Nicholl -Lee-Nicholl's improved ELC algorithm and FLC algorithm, etc. Relatively speaking, there are few methods for arc clipping in rectangular windows, and the existing arc clipping methods are essentially realized by solving quadratic equations in one variable; however, due to the complexity of solving arc algebraic equations, t...

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Problems solved by technology

However, in the actual research process, it is still found that the arc bounding box and the endpoint can be used for the arc correlation test, but there are the following difficulties: 1. The nonlinear characteristics of the arc bring additional bounding box calculation overhead, which is not conducive to eliminating as soon as possible and reserved; 2. The arc bounding box is generally large, and it is difficult to exclude or retain as many arcs as possible; 3. Even if both ends of the arc fall within the rectangular clipping window, the arc may still intersect with the window; 4. Even if both ends of the arc fall outside the rectangular clipping window, the arc may intersect with the window

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