Loft v. Extrude

Something that has puzzled me so I thought I would ask.

In the attached I have three identical closed polylines. At the top I have lofted a pair.
At the bottom I have extruded one.

The loft has created a separate surface for each curve segment.The extruded surface has the two upper facets merged. Why is that the case?

Problem Loft 6.3dm (3.1 MB)

Hi -

To ensure that this is created as two separate surfaces, run the CreaseSplitting and select the Enable option before running the ExtrudeCrv command.
-wim

I’m not getting any difference.

Hello - the file angle tolerance is .001, the polyline segments are ~.7 degrees off,

image

so Loft does not merge those segments. Extrusions use it’s own tolerance, apparently - if you set useExtrusions to make polysurfaces, you’ll get the same as the loft, or if you set the angle tolerance to 1, the loft will merge the segments.

-Pascal

Thanks, my preference is to not merge the surface as that is a specified knuckle point.

UseExtrusion=PolySurfaces does add the knuckle to the extrusion.