Equal Arclength
The Equal Arclength direction method allows the projection of curves from an X-Y coordinate system to the u-v isocurve coordinate system on a face, preserving the curve arclengths in the X (or u-isocurve) direction or the Y (or v-isocurve) direction. See the figure below for an example. Not available for sheet bodies or planes.
The projection utilizes only a single face, which you must select before choosing the Equal Arclength direction method. Also, the 'face' you select must be a face, and not a sheet body, plane or datum plane. If you select additional faces (and/or planes), they are ignored for the equal arclength projection.
A reference point on or near the X-Y plane of the curves is required. This must be an existing point entity.
After selecting a face and specifying the Equal Arclength method, select the reference point and specify a projection vector using the vector common tool.
Next, the Cue line prompts you to specify an X vector that corresponds to the u direction on the face. After you have done this, the system then displays the v-isocurve vector on the face.
The reference point and the projection vector and the X vector define the X-Y plane (the Y vector is orthogonal to the projection vector and to the X vector). The curves selected should be on (or parallel to) this plane in order for arclength distances to be preserved by the projection.
The new u and v coordinates of the projected (x,y) points depend on the Equal Arclength option. You may choose from the following: Both X and Y, First X, then Y, First Y, then X, X Only or Y Only.
Both X and Y - u is determined by measuring an arclength distance of x along the u-isocurve, and v is determined by measuring an arclength distance of y along the v-isocurve. The projection of a line in the X-Y plane, through the reference point and along the X-vector or the Y-vector will have an arclength equal to the line's length.
First X, then Y - First u is determined by measuring an arclength distance of x along the u-isocurve, then an arclength distance of y is measured along the v-isocurve to determine v. The projection of a line in the X-Y plane through the reference point and along the X-vector will have an arclength equal to the line's length. The projection of any line in the X-Y plane parallel to the Y-vector will have an arclength equal to the line's length.
First Y, then X - First v is determined by measuring an arclength distance of y along the v-isocurve, then an arclength distance of x is measured along the u-isocurve to determine u. The projection of the line in the X-Y plane through the reference point and along the Y-vector will have an arclength equal to the line's length. The projection of any line in the X-Y plane parallel to the X-vector will have an arclength equal to the line's length.
X Only - u is determined by measuring an arclength distance of x along the u-isocurve, and v is determined by measuring a distance of y along the surface tangent vector in the v-isocurve direction. The projection of the line in the X-Y plane through the reference point and along the X-vector will have an arclength equal to the line's length. For a line in the X-Y plane parallel to the Y-vector, distance along the surface tangent vector in the v-isocurve direction is preserved.
Y Only - v is determined by measuring an arclength distance of y along the v-isocurve, and u is determined by measuring a distance of x along the surface tangent vector in the u-isocurve direction. The projection of the line in the X-Y plane through the reference point and along the Y-vector will have an arclength equal to the line's length. For a line in the X-Y plane parallel to the X-vector, distance along the surface tangent vector in the u-isocurve direction is preserved.
Projection onto a face, or portion of a face, that is not smooth or is almost normal (orthogonal) to the projection vector may not work well. Also, if the projection would extend over the edge of the face, the projection curve may not be created.作者: yuanjunxhl 时间: 2005-8-10 06:20
投影中有等弧长这个命令作者: qsunny 时间: 2005-8-10 21:09
使用等弧投影，无法选取参数点，是不是因为用的盗版的阿！作者: vodka 时间: 2005-8-11 00:53
qsunny wrote:
使用等弧投影，无法选取参数点，是不是因为用的盗版的阿！
和D版无关。作者: 风里密码 时间: 2005-8-11 09:31
记得 n 年前作过一个动画，找找看
