共查询到16条相似文献,搜索用时 109 毫秒
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本文探索NURBS曲面求交及构造过渡曲面的方法。基于交线跟踪算法求出NURBS曲面间的交线,算法比较稳定、可靠;采用参数化平面与等距面求交找出两曲面空间等距点,具有自然与变半径过渡曲面的定义相呼应、找点快、准确、稳定的特点;过渡曲面表示为2×3次NURBS曲面,自然、充分地利用了NURBS曲线可精确表示圆弧段的特性,过渡曲面具有表达简单、比较准确、便于采用统一的NURBS曲面处理算法对其进行各种几何处理的优点;实验证明这些方法可行,效果令人满意。 相似文献
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参数曲面与平面求交的一种新方法 总被引:2,自引:0,他引:2
本文提出了一种新的参数曲面与平面求交算法,基于平面的半空间性质,通过参数域平面的二向线性插值,将求交问题转化为一系列简单的离散、判断、比较、排序等运算,能较好的解决曲面片内的交线不连续和交线丢失问题,算法简便,可靠性好,计算精度高,在NC自动编程中具有广泛的应用场合。 相似文献
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本文提出了一种新的参数曲面线投影求交计算方法,基于参数域摄动原理,将求交问题转化为一系列简单的参数摄动,映射,判断,比较等运算,能有效地解决参数曲面的线投影求交计算,大量的应用的实例表明这一算法的可靠性好,计算精度高,摄动速度快,已在复杂曲面测量造型和数控加工质量分析中取得了良好的应用效果。 相似文献
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介绍了一种用于实现复杂场景高品质实时渲染的新算法。已有的研究表明,基于传统几何图元的渲染技术必然涉及到大量的求交与消隐计算,而这正是实现实时绘制的瓶颈所在。利用OpenGL虽然可以实现实时绘制,但这是建立在Z-Buffer技术的基础上,并且将场景尽可能地简化来实现实时绘制的一种基于传统几何图元的绘制技术。这样渲染而得的图像质量很低,很难再现纹理及材质的特殊光照效果。笔者将图像与体图形学技术相结合,研究并实现了基于表面元素(Surface elements,即Surfels)的渲染技术,避免了耗时的求交计算,因此大大提高了复杂几何场景的绘制时间。又因为surfels中包含完整的材质属性和纹理信息,从而确保了在快速重绘时的图像质量。 相似文献
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根据线段两端点相对于圆形窗口的可能位置讨论裁剪结果。当两端点都在圆形窗口之外时,通过圆切线斜率与线段斜率的比较,及点区域判别来判断线段与窗口的相交情况。在确定线段与圆形窗口有交点的情况下,应用参数化形式求交运算,简化求交方程的构造。实验结果表明,新算法显著提高了裁剪效率。 相似文献
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A practical method for a noncontacting and real-time feature extraction for personal authentication is proposed. The finger geometry and feature extraction of the palmar flexion creases are integrated into a small number of discrete points based on the anatomical observation. For a video image of either palm, a palm placed freely facing toward a video camera is acquired. The fingers are brought together, and the palm is straightened out to eliminate any constraints. The discrete feature points for the fingers involve intersection points of the three finger (digital) flexion creases on the four finger skeletal lines. The feature points for the palm involve intersection points of the major palmar flexion creases and/or prominent creases of the palm on the extended finger skeletal lines. The orientations of the creases at the intersection points are also extracted features to be matched. The matching results are perfect for about 500 palm samples from 50 subjects so far. This discrete point processing, requiring no time-consumptive palmprint image analysis and requiring less than one second processing time, will contribute to a noncontacting, real-time and reliable feature extraction, easily combinable with other traits, for the personal authentication. 相似文献
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构造两个曲面的拼接曲面 总被引:1,自引:1,他引:1
给出了当两个待拼接曲面的拼接线具有参数化形式或者可以参数化时,它们之间 G1光滑拼接曲面的构造方法。所得的拼接曲面是由一个空间曲线集定义的,每一条空间曲线由拼接线上的点对确定。并且拼接曲面都是参数曲面,它们的形状可以通过预设的参数很好地调整和控制。作为实例,讨论了两个截口是平面的或非平面的(由两个二次曲面定义)的二次曲面之间的拼接曲面的构造和一般的参数曲面的拼接曲面的构造。 相似文献
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Bert Jüttler Pavel Chalmovianský 《Applicable Algebra in Engineering, Communication and Computing》2007,18(1-2):151-168
We describe a method to approximate a segment of the intersection curve of two implicitly defined surfaces by a rational parametric
curve. Starting from an initial solution, the method applies predictor and corrector steps in order to obtain the result.
Based on a preconditioning of the two given surfaces, the corrector step is formulated as an optimization problem, where the
objective function approximates the integral of the squared Euclidean distance of the curve to the intersection curve. An
SQP-type method is used to solve the optimization problem numerically. Two different predictor steps, which are based on simple
extrapolation and on a differential equation, are formulated. Error bounds are needed in order to certify the accuracy of
the result. In the case of the intersection of two algebraic surfaces, we show how to bound the Hausdorff distance between
the intersection curve (an algebraic space curve) and its rational approximation. 相似文献