Offset srf fail

Hello,

Rhino fails when i want to offset surfaces outwards 10mm to create solids (rings)…

cantoffsetsrrf.3dm (1.3 MB)

I think the problem is that you are too far away from origin (1403791458.82 millimeters).
I’ve moved alla to 0.0.0 and it seems to work (some surfaces need to be fitted to tolerance to have a good offsetsrf).

cantoffset_trynow.3dm (1.5 MB)

even at 0 many fails. what do you mean by “fit to tolerance” ?

FitSrf
If you run the command and push F1 the help will show how it works.
Another way could be rebuild surface… there are many commands that can fix the surfaces.

i will try but at first glance they seem fairly simple (shouldnot have these problems)… i made it by lofting two intersection curves (bridge main cable brep and plane) in GH.

Hello - you have many stacked control points on the surface.
How were these made?

-Pascal

Working at big distances from origin can cause a lot of problems so could be that the intersection curves were bad from the beginning.
To say what’s wrong we should see how the bridge main cable is modeled (if the surface is bad and you intersect it with a plane, the curves you’ll obtain will be bad as well).

BTW, if you are using GH, could be a good thing to fit or rebuild the curves you obtain from the cable before you use the loft command; this could give a better surface.

intersection of plane and brep (main cable of bridge).

yes thanks for the tip, i will rebuild intersection curves inside GH to achieve lighter loft surfaces. but still what pascal showed. is such density of CPs considered too heavy to cause issues with simple offsetsrf?

The problem Pascal pointed to is that there are CP that are duplicated (multi knot).
You can remove them with RemoveMultiKnot command.
To understand why they are created we have to see the original surfaces.