lofting or sweeping along a helix

[tricky]

I have always hated loft objects in Max (ever since version 1 I think!!!). I can never understand the way it seems to orient the underlying shape and paths - it never seems logical.

I attach a tiny part of a scene where I am trying to loft/extrude/sweep a rectangle along a helical path. Can anyone do this and tell me how they did it? For me, it just goes crazy!

spiral sweep.zip

Its a Max 2012 scene by the way.

[rivoli]

once you do the lofting, picking the rectangle as shape, go into the loft sub ojb menu and select shape. you can then reorient it so that it matches the rectangle's position. since the spiral path has already many corner vertices, you don't need any path step, so you can set that to 0 in the loft's skin parameters. this way it worked for me, I can send you back the scene if you want to have a look at it. what's good for me, might not be enough for you, and you may need to find a different solution..

[tricky]

I just can't get the loft to be accurate working like this. Why doesn't the shape just stay where it is instead of acquiring an apparently random rotation when added to the loft object? I can manually rotate it so its about right, but the error in the alignment is exaggerated higher up the path. Can't the shape be made to snap to the original location?

[muoto]

what about making your helix spline, extrude, and shell it ?

[Morne]

just do the helix in AutoCAD and do a sweep, works perfect (its a bit of a mission to draw the helix like you want due to ackwards commands, then have to convert it to a polyline)
OR
in max do a AEC stair object without the steps, also will work (a bit quicker in this case than AutoCAD)

[rivoli]

I can manually rotate it so its about right, but the error in the alignment is exaggerated higher up the path. Can't the shape be made to snap to the original location?

in my case the shape was aligned to the path, but yes, I had to try and match its position by hand. it's not very precise.. don't know of any method to make it snap to the starting rectangle. tried to reset both splines xform and collapse, but it didn't help..

[tricky]

Yep - tried doing it in Autocad - that's where the splines came from. The problem I have with Autocad was that I needed to make sure the cross section was NOT aligned to the spline when it is swept along the path. In wireframe, the result looks perfect, but in shaded (and after import into Max), the underside of the swept geometry is severely stepped. I couldn't figure out how to increase the resolution/steps in the sweep (tried messing with surftab1 and surftab2 variables for example) so I had to give up.

Any suggestions?

[tricky]

in my case the shape was aligned to the path, but yes, I had to try and match its position by hand. it's not very precise.. don't know of any method to make it snap to the starting rectangle. tried to reset both splines xform and collapse, but it didn't help..

Yes - I tried XFORM too, but no help. This should be so easy.

[Morne]

in AutoCAD:
sweep (enter)
select profile (enter)
A (enter)
N (enter)
B (enter)
click base of profile where it starts on the path
click path
done

no need to worry about surftab1 or surftab2

[Ramsay]

I rebuilt your splines in Max and it seems to work fine. It also means you can tweak the helix if you like as the base parameters are still there. Here's the file - http://dl.dropbox.com/u/25822301/spiral%20sweep03.zip

[tricky]

in AutoCAD:
sweep (enter)
select profile (enter)
A (enter)
N (enter)
B (enter)
click base of profile where it starts on the path
click path
done

no need to worry about surftab1 or surftab2

Yep - tried this. I get a horrible 'stepping' on the underside of the sweep. Wireframe looks great, but shaded (and import into max) looks wank.

[Morne]

and in AutoCAD if you instead of do a "shade" do:
vscurrent
s
or instead of s try e

does it still display with a step?

[sduck]

Have you checked FACETRES system variable in AutoCAD? The default is .5 but you can take it up to 10. This adjusts smoothness of shaded and hidden line objects but also impacts how a mesh exports.

[tricky]

Have you checked FACETRES system variable in AutoCAD? The default is .5 but you can take it up to 10. This adjusts smoothness of shaded and hidden line objects but also impacts how a mesh exports.

Bugger - that's a setting I haven't used for a few years! I'd forgotten about that little easter egg. Let me give it a try.

We have a winner - it seems FACETRES is the culprit. Thankyou all!