I’m again trying to up my skills. So I’m trying to make this piece. I’ve been at it for a while. After much trial and error to get the tapered tight turns, I thought I had it. (the object with the bottom) However, when I tried to apply a 5mm filet to the bottom edge it failed. Looking closely at the tight turns, there is something off. I decided to go back to the original curves I used for the 2 rail sweep. These were made using BlendCrv with tangency 1&2. Anyway, I split them and mirrored to ensure they were symmetrical. The new sweep is even worse. (the object without the bottom) The second image is what O got lofting the curves. Obviously something is wrong with the corners, but I don’t kno where to start. Where am I going wrong?
on 2 spots, what i like to do when things behave strange like this i use osnap end and check the curves if it has any strange movable snaps there is some issue there
@CalypsoArt In BlendCrv is CurveEnd or PickPoint selected? If PickPoint is selected then the blend curve will start where you pick the curve, which may not be at the end of the curve. You need to use CurveEnd (unless you follow-up the blend by trimming the input curve(s).)
Thanks for the responses. BlendCrv is set to CurveEnd, Trim and Join. I just reworked it. Again, I split and mirrored for symmetry.
Pic 1 is what I get with the Sweep2. Pic 2 is what I get after I try to apply a 5mm filet. Pic 3 is some sort of blemish, which I assume is caused by bad geometry.
Jim, yes, that is what I’m trying to get. I’ve never used ExtrudeSrfTapered. I’ll look into it. Right now I can’t see how to specify the taper.
Also, your model does not filet correctly for me using FiletSrf. I pick the base as the first surface, but the wall is four surfaces, and I can pick them all, so I get partial fileting. It did work with FiletEdge.(ChainEdges)
Too coarse a render mesh, not bad geometry.
Correction: there is bad geometry which leads to the need for a more refined render mesh. The curvature comb shows there is a problems with the curve.
For a uniform height tapered extrusion (uniform taper angle) the offset in the plane normal to the extrusion direction will be uniform, equal to the extrusion distance * tangent (extrusion angle). For your example that offset should be 4.44.
That’s curious because one of the main surfaces had 5 degrees draft and the other had 10 degrees draft. I assumed that was not by accident.
I did reconstruct the arcs. Your arcs were a bit off with internal discontinuities so reconstructed them.
Extrude Taper is not an easy command to use. Its one of those surface modeling tools that has been ignored for decades. It only really works well on planar lines and arcs that are tangent, but the input curves need good G1 continuity.
If you wanted to make everything with the same draft angle you could use extrude taper for all the curves all the way around in one go. But since there are two different draft angles you have to do them separately and the connecting surfaces can’t have a constant draft angle
If you are using Rhino8 or earlier you have to run FilletSrf 4 times to make each fillet. In the Rhino WIP FilletSrf has the ContinueAcrossFaces option that will make all the fillets at once.
