Sweep1

Sweep1 指令旨在沿着一条路径扫掠通过数条定义曲面形状的断面曲线建立曲面。

步骤

选取一条路径曲线。

依照曲面通过的顺序选取数条断面曲线。

附注

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开放的曲线需要点选同一侧。

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封闭的曲线可以调整曲线接缝。

技巧

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每条断面曲线的结构都相同才可以建立品质良好的扫掠曲面，使用重新逼近公差选项时，所有的断面曲线会以三阶曲线重新逼近。

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未使用重新逼近公差选项时，所有断面曲线的阶数与节点会一致化，但形状并不会改变。您可以使用重新逼近公差设定断面曲线重新逼近的公差，但逼近路径曲线是由文件属性 > 单位 > 绝对公差控制。

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以封闭的路径曲线建立封闭的扫掠曲面时，您选取的第一条断面曲线同时也是最后一条断面曲线。

指令行选项

ChainEdges (rails only)

Select connected edges based on the curve continuity of the connection between segments.

连锁边缘选项

Inside a command that accepts chain selection, type chain.

Select first chain segment.

Chain options

自动连锁

选取一条曲线或曲面边缘可以自动选取所有与它以连锁连续性选项设定的连续性相接的线段。

连锁连续性

设定自动连锁选项使用的连续性。

方向

向前

选取第一个连锁段正方向的曲线/边缘段。

向后

选取第一个连锁段负方向的曲线/边缘段。

两方向

选取第一个连锁段正、负两个方向的曲线/边缘段。

接缝公差

如果两条曲线或两个边缘的端点距离比这个数值小，连锁选取会忽略这个接缝继续选取下一个连锁段。

角度公差

当连锁连续性设为正切时，两条曲线或两个边缘段接点的差异角度小于这个设定值时会被视为正切。

Undo

依次复原最后选取的线段。

下一个

选取下一个线段。

全部

选取所有线段。

Point (cross-sections only)

The Point option creates a surface that begins or ends at a point. Use this option only at the start or end of the curve series.

单轨扫掠选项

型式

自由扭转和走向选项决定断面平面是如何沿轨迹分布的，在很多情况下，所有选项得到的曲面是相同的。

自由扭转

扫掠建立的曲面会随着路径曲线扭转，自由扭转通常使用路径切线与曲率方向的相交作为框架平面。

走向 Top / Right / Front

单轨扫掠走向选项基于路径切线方向与此选项指定的固定方向来计算断面沿路径的分布。走向 Top 设置固定方向为世界坐标轴的 Z 方向，Front 使用 Y 反向，Right 使用 X 方向。

Technical notes

To determine the movement of a cross-section, one frame is found at an existing cross-section location and another is calculated at the desired location along the rail. The difference between those frames defines the movement of the cross-section.

A frame is a 3-D point and three direction vectors. It can be drawn as something that looks like the Rhino world axes icon. It describes a unique coordinate system in space.

The frames are found like this:

The rail tangent and the fixed direction vector (if they are not parallel) define a plane. The cross product of the tangent vector and the fixed direction produces the normal vector of that plane (frame x) perpendicular to both of the input vectors.

The cross product of frame x and the rail tangent produces another vector, frame y, perpendicular to the tangent and frame x.

Taking the rail tangent as frame z, there is a unique 3d frame at a specific location along the rail with its mutually perpendicular x, y and z coordinate directions.

The rotation and translation between two of those frames determines how a cross-section will be moved from one location on the rail to another.

If the rail tangent and the arbitrary vector are parallel, they do not define a plane and the cross product does not produce a vector, so the frame is under-defined, and it will twist around the rail tangent since that is the only defined information.

For the Right and Front options, the same orientation rules apply with respect to those construction planes.