Issues with offsetting surface

I'm currently having some issues offsetting a single, trimmed surface. The goal is to offset the original surface in order to derive lofted surfaces connecting the original and the offset surface so that those side surfaces might trim a third, already defined surface. In this case, the green surface shown would offset to trim the red surface.

However, as noted by some others on these forums, offsetting trimmed surfaces in grasshopper seems to operate much differently in grasshopper than in rhino. To be clear, I don't actually require the offset surface itself, but rather the side surfaces that would connect the original and the offset surfaces. Additionally, the offset works okay within certain ranges, but does not work beyond a certain distance, whereas in rhino the commands work just fine with the same surfaces. I see two options (there may be other approaches I hadn't considered);

1) Find a workaround for offsetting the surface.

2) Find an analogue to "OrientCrv" in grasshopper. Use that to array lines on the surface normal at the edges. Sweep1 using normal-oriented lines as cross-section curves. Use swept surfaces to trim lower (red) surface.

Any thoughts or input are greatly appreciated, as I've been productively failing for the past 6 hours. I assure you, I've scoured forums and tried multiple work-arounds and custom components - It just seems that the offsetting of surfaces fails at a given distance for this surface.

Thanks!

Attachments:

offset.3dm, 458 KB
offset.gh, 5 KB

Replies to This Discussion

Permalink Reply by Joseph Oster on October 12, 2015 at 3:40pm

Here are three possibilities:

P.S. I internalized the two 'Srf' parameters so the Rhino file isn't needed.

Attachments:

offset_2015_Oct12a.gh, 178 KB

Permalink Reply by brad thomas on October 12, 2015 at 3:54pm

Remarkable! Thanks, Joseph! I believe the "pull" option works best for my purposes. Do you know if it "pulls" normal to the lower surface or the top surface?

Permalink Reply by Joseph Oster on October 12, 2015 at 4:24pm

I assume that it pulls to the closest point, all along the curve? Not sure, really.

Permalink Reply by brad thomas on October 12, 2015 at 4:27pm

Thanks, Joseph. Will do some tests and try to figure it out.

Permalink Reply by Kyle Faulkner on October 13, 2015 at 1:31pm

A little late to the party, but here might be another option. This generates edges "extruded" surfaces normal to the original surface.

Attachments:

offsetEdge.gh, 10 KB

Permalink Reply by Joseph Oster on October 13, 2015 at 1:51pm

Nice! I wonder how different that is from the 'Pull' method I posted? Oh, wait, I see a big difference... 'Pull' takes the edge curves to the surface while your method uses a distance offset. Well done.

Permalink Reply by brad thomas on October 13, 2015 at 2:29pm

Excellent!

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