I’m trying to sweep a bridge cross section of varying width. I’m not satisfied with the default way the outer edges of the resulting solid are handled - they seem to always be perpendicular to cross sections, which means that on a segment of varying width the edges are S-shaped. I need the edge to stay linear with respect to the sweep rail.
I’ve reduced the problem to a simple example:
A straight line in the XY-plane for the sweep rail.
Same cross section inserted to both ends of rail.
Width of the end cross section reduced significantly on one side.
The resulting S-shape of the corresponding edge is visible in the screenshot. How can I make it a straight line using the Sweep1 command (in this instance I can use Loft, but the bridge axis is, generally, much more complex)?
Thanks, that does work for this simplified example, but that’s not what I’m after. Unless I can loft along a rail curve, it won’t work for a general bridge geometry. The change of width might be happening along a circular arc or worse which can even have parabolically varying elevation.
Although it’s preferable to design the bridge in such a way that the width changes occur on straight segments only, this is not always possible. The internet is full of tutorials on how to model bridges in Rhino/Grasshopper, but I haven’t found any that deal with difficult spacial constraints.
For the sake of completeness, Sweep1 with global shape blending works for the straight rail, but it doesn’t work as desired for an arced rail.
In another example, I used an arced rail and an intermediate cross section. Between Start and middle, the width is constant and then it decreases so that the inner edge remains straight. Global shape blending actually deformed the edge even more than the default setting, see below.
I’m not happy to have to construct the edge curves, but there seems to be no way around it. Now that I have modelled it, I can see that the narrowing edge isn’t actually linear with respect to the center axis.
i am shocked that there is no option to create straight loft along curve?
i have a path curve and sections i want to lof between, i need straight connection not tangential on longitudinal direction. i would bet my life this must be possible because its the simplest case and i cant seem to be able to construct it…
i have to manually sweep1 with global blending option between only 2 adjacent crossections multiple times.
it is a shame there is no option directly in options to get this! we need simple loft multiple crosssections along curve option.
